Keywords : dielectric properties


Influence of Processing Induced Morphology on the Performance of PP Injected Intricate Pieces Modified with MWCNT as a Painting Aide

Alejandra Costantino; Leandro Ramajo; Julio Viana; Caren Rosales; Antonio Pontes; Valeria Pettarin

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-10
DOI: 10.5185/amlett.2021.041618

Carbon nanotubes are currently added to polymers to avoid extra-stages in the electrostatic painting process. However, the attained particle network after processing a final part could affect the mechanical properties and thermal stability of nanocomposites. It is then important to evaluate not only the functional properties, but also the overall performance of these pieces. In this work, boxes of polypropylene (PP) modified with multi-walled carbon nanotubes (MWCNT) were injection molded. Morphology induced by processing was characterized at different locations of the moldings to correlate the influence of in-homogeneities and flow pattern with the overall performance of the molded boxes. PP/MWCNT presented a better aesthetic quality and a markedly better thermal stability than pure PP. It was confirmed that the nanocomposite has high dielectric permittivity, low dielectric losses and relatively good DC conductivity. Regarding mechanical properties, MWCNT induced a slight improvement in flexural elastic modulus. Although fracture initiated at practically the same loading levels for both materials, the propagation energy was deteriorated by MWCNT presence. Differences in both electrical and mechanical behavior were found trough out the PP/MWCNT pieces as result of distinct MWCNT orientation and distribution. It was then concluded that processing has a great influence on parts performance.

Structural, Optical and Electrical Properties of CaSnO3 and Ca0.98Nd0.02Sn0.98Ti0.02O3 Synthesized using Sol-Gel Method

Aditya Kumar; Bushra Khan; Gulab Singh; Manoj K. Singh; Upendra Kumar

Advanced Materials Letters, 2021, Volume 12, Issue 3, Pages 1-9
DOI: 10.5185/amlett.2021.031611

Single phase sample of CaSnO3 and Ca0.98Nd0.02Sn0.98Ti0.02O3 were synthesized by sol-gel route followed by calcination at 800 o C. The X-ray diffraction pattern of both samples showed monophasic, and their Rietveld refinement studies indicated that the samples belonged to orthorhombic crystal structure under space group Pbnm. Moreover, dopant substitution results in unit cell compression due to lower ionic radii of dopant than host. UV-Vis. spectroscopy study of samples reflected semiconducting samples. The direct optical band gap of doped sample found smaller (4.02 eV) than undoped (4.23 eV), due to formation of Nd 3+ state below conduction band. The dielectric constant of both samples (30 and 18) was found to be temperature independent up to 220 o C and 300 o C and tangent loss below 1 makes it suitable candidate for thermally stable capacitor application. Ac conductivity of samples was analyzed using Arrhenius model as a function of frequency and temperature, and the value of activation energy is reflected an electronic as well as mixed ionic and electronic conduction in samples. Based on these studies, the present material can be used in UV-filter, sensors, and mixed ionic and electronic conductor applications.

Dielectric Relaxation and Suitability of Scaling parameters study on Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0 - 0.3) Ferrites

Nimish H. Vasoya; Kiran G. Saija; Akshay R. Makadiya; Tushar K. Pathak; Urmila M. Meshiya; Pooja Y. Raval; Kunal B. Modi

Advanced Materials Letters, 2020, Volume 11, Issue 12, Pages 1-8
DOI: 10.5185/amlett.2020.121587

The compositional dependence of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity (ε*) and loss tangent (tan d) for Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0, 0.1, 0.2 and 0.3) spinel ferrite series was investigated over wide frequency (f = 20 Hz to 1 MHz) and temperature (T = 300 K to 673 K) ranges. Frequency dependence of ε',ε'' and tan δ has been explained based on the two-layer model of dielectrics. The nonlinear relationship between ε'(f) and σ'(f) suggests multi-relaxation process and formation of a broad hump in ε'(f, T) plots indicates collective contributions from electrons and holes to the polarization. The scaling by normalized frequency (f/fc) and scaled frequency (f/σdc) are found successful for ε' in high-frequency regime only while scaling found successful for ε'' over the whole range of frequency. The suitability of various scaling parameters was also tested for the master curve generation. The co-existence of localized and delocalized relaxations is verified.

Effects of Silica Modified NiFe2O4 on the Dielectric and Electrical Properties of NiFe2O4 filled Poly (methyl methacrylate) Composites

Srikanta Moharana; Anjali Kujur; Sudhir Minz; R. N. Mahaling; Banarji Behera

Advanced Materials Letters, 2020, Volume 11, Issue 2, Pages 57-62
DOI: 10.5185/amlett.2020.021480

Nickel ferrite [NiFe2O4 (NFO)] nanoparticles were synthesized using a simple precursor based chemical route and modified with tetraethoxysilane (TEOS) to form SiO2 layer adsorbed on the NFO particles (SiO2@NFO). Based on the nanoparticles, the SiO2@NFO-PMMA composite films were prepared embedded with SiO2@NFO nanoparticles in a poly (methylmethacrylate) (PMMA) matrix. The properties of the composites were characterized extensively using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, dielectric and electrical measurement. FTIR analysis showed that the SiO2 groups had been successfully introduced into the NFO nanoparticles. The SEM images of the SiO2 adsorbed NFO nanoparticles had better dispersion in the PMMA matrix than the unmodified one. The SiO2 modified NFO-PMMA composites had much higher dielectric constant and better suppressed dielectric loss than the other two phase composite systems. The maximum dielectric constant was up to ≈ 67 while the dielectric loss was controlled below 0.5. This study suggested that the SiO2 modified NFO-PMMA composite films with high dielectric constant and low loss might be promising candidates for application in microelectronic engineering.  

Determination of leachate pollution content in soil using in-situ dielectric measurement  

Mohammed Dahim; Rabah Ismail; Hashem Al-Mattarneh; Randa Hatamleh

Advanced Materials Letters, 2019, Volume 10, Issue 4, Pages 298-301
DOI: 10.5185/amlett.2019.2253

This paper presents the development of an electromagnetic probe to accurately measure the soil electromagnetic properties such as dielectric constant and loss factor in the field. The in-site dielectric probe sensor is designed and methods have been developed to calibrate and validate the accuracy of the sensor in measuring dielectric properties of the material. Clean saturated sandy soil material with porosity 40% was used. The soil samples were contaminated by leachate from municipality solid waste from the landfill site. Five levels of leachate contamination were prepared, ranging from 0% to 10%. Dielectric properties of soil polluted sample were measured using the proposed in-site dielectric sensor. Dielectric properties of contaminated soil were evaluated at a different frequency and leachate content. The result showed that both dielectric constant and loss factor decree with increasing frequency due to the reduction of conductance current at high frequency. Also, the result showed that the dielectric properties of leachate-contaminated soil decrease with increasing leachate content while the loss factor increase with increasing leachate content. Mathematical models were developed to determine the relationship between soil dielectric constant, loss factor and soil leachate pollution content.

Magnetic and dielectric properties of divalent Ca2+ and Ba2+ ions co-doped BiFeO3 nanoparticles

N. Manjula; S. Ramu; K. Sunil Kumar; R. P. Vijayalakshmi

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 175-181
DOI: 10.5185/amlett.2018.1411

Pristine BiFeO3 (BFO) and Ca doped BiFeO3: Ba nanoparticles (NPs) were synthesized in aqueous solution by sol-gel method with Tartaric Acid as a chelating agent. EDAX measurements confirmed the presence of Ca, Ba in the BiFeO3 host lattice. X-ray diffraction analysis showed that the average grain size of the prepared samples was in the range of 09–28 nm. The lattice structure of the nanoparticles transformed from rhombohedral to tetragonal phase with Ca 2+ ions substitution increased. TEM images indicated that sphere and square shape of nanoparticles through a size ranging from 10 to 15 nm. Diffusion reflectance spectra of BiFeO3 NPs showed a substantial blue shift of ~100 nm (630 nm -> 530 nm) on Ca, Ba co-doping which corresponds to increase in band gap by 0.47 eV. Dielectric constant (ε’) and dielectric loss (ε’’) were measured in the frequency range 1 Hz to 1 MHz at room temperature. Dielectric constant and loss are increased with Ca concentration except for Ca (4 at. %). The bulk conductivity (σ) increases from 3.07 x 10 -6 S/m to 1.64 x 10 -5 S/m as the Ca concentration increased from 0.00 to 0.03. Magnetic measurements revealed the ferromagnetic character of Pristine BFO and Ca doped BiFeO3: Ba samples. It is observed that by increasing the Ca concentration the value of Mr and magnetization are varied irregularly upto Ca (4 at. %). But for x = 0.01 Mr and magnetization are highest. The values of magnetization and Mr for 1% Ca doped BiFeO3: Ba NPs are 2.99 emu/g, 1.54 emu/g, respectively, which are quite significant at room temperature. These materials have potential applications in data storage, switching devices, spintronics, sensors and microelectronic. 

Zeolite 4A Filled Poly (3, 4-ethylenedioxythiophene): (polystyrenesulfonate) (PEDOT: PSS) And Polyvinyl Alcohol (PVA) Blend Nanocomposites As High-k Dielectric Materials For Embedded Capacitor Applications

M. K. Mohanapriya; Kalim Deshmukh; M. Basheer Ahamed; K. Chidambaram; S. K. Khadheer Pasha

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 996-1002
DOI: 10.5185/amlett.2016.6555

Zeolite 4A nanoparticles were incorporated into Poly (3, 4 - ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS) and Polyvinyl alcohol (PVA) blend matrix to prepare PEDOT: PSS/PVA/Zeolite 4A nanocomposites using solution casting technique. The structure and morphology of nanocomposites were examined using Fourier transform infrared spectroscopy, X-ray diffraction, UV-Vis spectroscopy and Scanning electron microscopy. The mechanical and dielectric properties of nanocomposites were also evaluated. The FTIR and XRD results indicate the strong interaction between the Zeolite 4A nanoparticles and the polymer matrix. The SEM micrographs show the homogeneous dispersion of Zeolite 4A into the polymer matrix. The nanocomposite exhibits a high dielectric constant and low dielectric loss, which could be due to proper dispersion and good interaction between Zeolite 4 A and polymer matrix. Thus, based on the results obtained it can be concluded that PEDOT: PSS/PVA/Zeolite 4A nanocomposites can be used as a flexible dielectric material for embedded capacitor applications.

Correlative Exploration Of Structural, Optical And Electric Properties Of Colossal Dielectric Ni Doped Sm Orthoferrites

Sajad Ahmad Mir; M. Ikram; K. Sultan; Z. Habib; H. Kausar; K. Asokan

Advanced Materials Letters, 2015, Volume 6, Issue 12, Pages 1081-1087
DOI: 10.5185/amlett.2015.5959

Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain size (0.2 μm to 0.3 μm) with an increase in Ni doping. The influences of Ni doping on optical energy band gap are investigated in the wavelength range of 200-800 nm. Dielectric properties (dielectric constant and loss) for SmFe1-xNixO3 were studied in the temperature range 100-400K and in the frequency range 20 kHz-1MHz. AC conductivity of pristine sample is found to be less than Ni doped samples. Various possibilities were explored to explain the observed dielectric and electric behavior of Ni doped SmFeO3 ceramics.

An Experimental And Numerical Investigation Of Tensile Properties Of Stone Wool Fiber Reinforced Polymer Composites

S.T. Leong; Y. Yusof; C.F. Tan

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 888-894
DOI: 10.5185/amlett.2015.5835

The present work focuses on determination of tensile properties of stone wool fiber reinforced high density polyethylene composites by two methods: experimental and finite element analysis. Four weight percentage of stone wool (SW) fiber 10 – 40 wt. % were chosen. The samples of composites were made by using the hot press technique. ASTM D638 was used to test the composite samples. Scanning electron microscopy analysis was carried out on the fractured surface to observe the interaction between matrix and fiber in the composites. Significant improvement of tensile properties was observed and recorded from the composites with SW weight percentage of 20 wt. %. The yield strength, tensile strength and tensile modulus increased by 8.1%, 23.0% and 37.8% over pure HDPE. ANSYS tensile models were then established to understand better the processing and behavior phenomenon. The numerical results obtained were in good agreement with the experimental results, with an accuracy of more than 90%.

Dielectric Properties Of Pr6O11 Nanorods Grown Chemically At Low Temperature And Atmospheric Pressure

Lalit Sharma; Partheepan Ganesan; Ranjit Kumar; T.D. Senguttuvan; Vidya N. Singh

Advanced Materials Letters, 2015, Volume 6, Issue 9, Pages 779-782
DOI: 10.5185/amlett.2015.5848

Due to high dielectric constant, Pr6O11 is viewed as a prospective gate dielectric material in decanano metal-oxide-semiconductor devices. In this study, structural, optical and dielectric properties of Pr6O11 nanorods have been investigated for its possible application as gate dielectric materials for the future generation optoelectronic devices. Pr(OH)3  nanorod structure was synthesized in an alkaline medium (KOH and NaOH) at a moderate temperature (~188°C) and atmospheric pressure. The Pr(OH)3 nanorods were converted to Pr6O11 nanorods by annealing them at 400°C. XRD studies showed that both Pr(OH)3, as well as Pr6O11, were highly crystalline. TEM studied showed that the diameter and length of nanorods were ~30 nm and 100 nm, respectively. Optical studies showed that the band gap of these nanorods is 5.31eV. Dielectric studies showed that dielectric constant at 1 kHz is ~ 4000.

Effect Of Grain Size On The Structural And Magnetic Properties Of Nanocrystalline Al3Fe5O12 By Aqueous Coprecipitation Method

S.E.Naina Vinodini

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 717-725
DOI: 10.5185/amlett.2015.5874

Al3Fe5O12 (AIG) nanopowders were synthesized at different pH using aqueous co-precipitation method. The effect of pH on the phase formation of AIG is characterized using XRD, TEM, FTIR and TG/DTA. From the Scherer formula, the particle sizes of the powders were found to be 15, 21, 25 and 30 nm for pH= 9, 10, 11 and 12, respectively. It is found that as the pH of the solution increase the particle size also increases. It is clear from the TG/DTA curves that as the pH is increasing the weight losses were found to be small. The nanopowders were sintered at 900°C/4hrs using conventional sintering method. The phase formation is completed at 800°C/4h which is correlated with TG/DTA. The average grain size of the samples is found to be ~55 nm. As the pH increases the magnetization values are also increasing. The saturation magnetization was found to be 4 emu/g, 6 emu/g, 7 emu/g and 9 emu/g corresponding to pH= 9, 10, 11 and 12, respectively which clearly shows that the magnetization values are dependent on pH. Room temperature magnetization measurements established these compounds to be soft magnetic.  The dielectric and magnetic properties (εʹ, εʺ, µÊ¹ and µÊº) of AIG was studied over a wide range of frequency (1GHz-50GHz). With increase of pH both εʹ and µÊ¹ increased. This finding provides a new route for AIG materials that can be used in the gigahertz range.

 Dielectric Diffuseness And Conductivity Behavior Of Ba1-xCuxTi1-x(AlK)xO3 Nanoceramics Prepared By Chemical Route

Prasanta Dhak; A. Kundu; K. Pramanik; P. Pramanik; D. Dhak

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 492-500
DOI: 10.5185/amlett.2014.5752

Small amounts of Cu and Al-K substitution on the A and B site of BaTiO3, respectively resulting a solid solution of the type Ba1-xCuxTi1-x(AlK)xO3 (BCTAK) [x = 0.05, 0.10, 0.15, 0.20] have been investigated. The compositions have been prepared in the nanocrystalline range by chemical route. X-ray diffraction revealed the tetragonal (P4/mmm) phase. Average crystallite size and particle size were found to be in the range between 25 nm and 35 nm which were analyzed through X-ray diffraction and transmission electron microscopy respectively. A dielectric study of these compounds as a function of temperature suggested that with increasing substitution concentration the dielectric constant decreased and the Curie temperature shifted towards the lower temperature side. Discontinuous grain growth accompanied with excellent dielectric diffuseness was found with increasing concentration of substitution. The dielectric diffuseness γ was found to be maximum to 1.91 at the substitution of BCTAK x = 0.20. The activation energy, Ea was found to decrease along with an increase in conductivity with increasing substitution concentration in BCTAK.  

Characterisation And Dielectric Property Analysis  of A-site Doped LaTiO3-δ Perovskites Synthesised by Ball Milling Method

Bradha Madhavan; Anuradha Ashok

Advanced Materials Letters, 2015, Volume 6, Issue 5, Pages 395-401
DOI: 10.5185/amlett.2015.5827

The present work highlights a series of perovskites La0.8A0.2TiO3-δ, (where A= Ba, Ca, Sr), which includes a high dielectric constant, a low dielectric loss over a wide temperature, in a frequency range of 30 MHZ. Undoped and A-site doped LaTiO3-δ (with Ba 2+ , Sr 2+ and Ca 2+ ) perovskites were synthesised by solid state reaction method (ball milling). The perovskite phase formation of the milled precursor powders under thermal treatments was investigated by thermogravimetry/differential scanning calorimetry (TG/DSC). Structural analysis of the phase pure sintered pellets revealed an orthorhombic crystal structure for all perovskites. Surface morphology of the sintered pellets exposed the presence of nanosized grains. The oxidation states of La 3+ and Ti 3+ ions have been confirmed using X-ray Photoelectron Spectroscopy (XPS). The dielectric spectral analysis reveals that dielectric properties of the perovskites depend on temperature and frequency. Among the dopants Sr is found to be the most effective in increasing the dielectric properties of LaTiO3-δ. This makes it suitable as a high dielectric material for making capacitors operating at higher frequencies.

Structural, Dielectric And Magnetic Properties Of 0.3CoFe2O4-0.7BaTiO3-PVDF Composite Film

Manjusha and K.L. Yadav; Manjusha;K.L. Yadav

Advanced Materials Letters, 2014, Volume 5, Issue 11, Pages 652-657
DOI: 10.5185/amlett.2014.4567

Structural, Dielectric and magnetic properties 0.3 CoFe2O4–0.7 BaTiO3–PVDF (polyvinylidene fluride) composite film with different concentration of PVDF: 20, 30 and 40 wt% are reported here for the first time. The structural analysis was carried out using X-Ray diffraction technique, which indicates cubic spinel structure for ferrite phase CoFe2O4 (CFO) and tetragonal structure for ferroelectric phase BaTiO3 (BT). The average grain size was observed to be (~106 nm, 30 nm and 26 nm) for 20%, 30% and 40% addition of PVDF by using AFM analysis. The dielectric constant variation with temperature at three fixed frequencies (1 kHz, 50 kHz and 100 kHz) was studied and it was found that the dielectric constant and dielectric loss decrease with increasing amount of polyvinylidene fluride. The values of ac conductivity for 0.3CoFe2O4 – 0.7BaTiO3 –PVDF composite film were found to decrease with increasing concentration of PVDF. The ferroelectric hysteresis loops also indicate that the value of polarization decreases with the addition of PVDF and the value of remnant polarization for 20% PVDF was found to be 0.5286 µC/cm 2 . The magnetocapacitance of 0.3 CoFe2O4–0.7 BaTiO3–0.3 PVDF was found higher for this composition.

Structural And Dielectric Properties Of Nb And Fe Co-doped PZT Ceramic Prepared By A Semi-wet Route

Arvind Kumar; S. K. Mishra

Advanced Materials Letters, 2014, Volume 5, Issue 8, Pages 479-484
DOI: 10.5185/amlett.2014.564

In the present work, detailed investigation of dielectric, piezoelectric and ferroelectric properties of Nb and Fe co-doped PZT ceramic near the MPB composition has been carried out. Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 (PFZTN) ceramics for x = 1- 6 mol% and y = 5.50 mol% have been prepared by a semi-wet route. X-ray diffraction studies confirm the formation of single phase perovskite structure. It is shown that Fe doping in PZNT improves the dielectric, ferroelectric and piezoelectric properties of ceramics. It has been found that at room temperature, dielectric constant and d33 start to increase up to the composition x = 0.05 and thereafter decrease. The maximum value of dielectric constant and d33 has been found for the composition x = 0.05. It has been shown that doping of Fe does not affect over the transition temperature uptown x = 0.04. The value of remnant polarization is of the order of 11.62 µC/cm 2 at x= 0.04. The investigated material seems to be promising candidate for multilayer capacitor applications.

 Study Of Ca Doping On A- Site On The Structural And Physical Properties Of BLTMNZ Ceramics

P. Kumari; R. Rai; A. L. Kholkin; A. Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 255-259
DOI: 10.5185/amlett.2013.10547

The ferroelectric Ca doped (Ba0.9575La0.04X0.0025) (Ti0.815Mn0.0025Nb0.0025Zr0.18)0.99O3 was prepared by a high-temperature solid state reaction technique. For the understanding of the electrical and dielectric property, the relation between the crystal structures, electrical transition and ferroelectric transitions with increasing temperature ( –160 to 35°C) have been analyzed. X- ray diffraction analysis of the powders suggests the formation of a single-phase material with monoclinic structure. Capacitance and tanδ of the specimens were measured in the temperature range from -160 to 35°Cat frequencies 1 kHz – 1 MHz. Detailed studies of dielectric and electrical properties indicate that the Curie temperature shifted to higher temperature with the increase in frequency. Moreover, the dielectric maxima dropped down rapidly initially and the dielectric peaks became extremely broad. The AC conductivity increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity.

Multiferroic Properties Of 0.05 NZF - 0.95 Ba0.9-3x/2Sr0.1LaxTiO3 Magnetoelectric Composites

Renu Rani; K. K. Raina;Chandra Prakash; J. K. Juneja; Sangeeta Singh

Advanced Materials Letters, 2014, Volume 5, Issue 4, Pages 229-233
DOI: 10.5185/amlett.2013.fdm.63

For the present work, the magnetoelectric (ME) composites with composition 0.05 Ni0.8Zn0.2Fe2O4 - 0.95 Ba0.9-3x/2Sr0.1LaxTiO3(NZF-BSLT) with x = 0, 0.01and 0.02 were synthesized by conventional solid state reaction route. The existence of both phases was confirmed by the X-Ray diffraction (XRD) technique. The dielectric properties such as dielectric constant and dielectric loss were measured as a function of temperature at different frequencies. P-E hysteresis loops and M-H hysteresis loops confirm the ferroelectric and ferromagnetic nature of the composite samples.La substitution in ferroelectric phase results in significant improvement in properties of composite samples. The investigated composites seem to be very attractive for multiple state memory devices where data can be stored both as polarization (P) and magnetization (M). 

Effect Of La And Pb Substitution On Structural And Electrical Properties Of Parent And La/Pb Co Doped BiFeO3 multiferroic

Poorva Sharma; Dinesh Varshney

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 71-74
DOI: 10.5185/amlett.2013.fdm.10

La/Pb co-doped BiFeO3 compounds were prepared by a solid-state reaction. X-ray diffraction of BiFeO3 (BFO), Bi0.725La0.1Pb0.175FeO3 [BLPFO] showed single phase in nature. BFO crystallize in the rhombohedral distorted perovskite structure (space group-R3c) while to that BLPFO crystallize in distorted pseudocubic (Pm-3m) symmetry which has been confirmed by the Rietveld refinement of the room temperature X-ray powder diffraction data. The effect of La/Pb substitution on dielectric constant, and loss tangent, of the samples was studied at room temperature in a wide range of frequency 10 Hz – 1 MHz. The room temperature dielectric constant of BFO (BLPFO) was 120 (200). Ferroelectric measurement reveals remnants polarization of BLPFO is about 0.24 μC/cm 2 at an applied field of 15 kV/cm. Weak ferroelectric effect is observed for co-doped BiFeO3 compound.

Microwave-hydrothermal Synthesis Of CoFe2O4-TiO2 Nanocomposites

P. Raju;S. R. Murthy

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 99-105
DOI: 10.5185/amlett.2013.icnano.130

The nanocomposites of x TiO2+(1-x)CoF2O4 (≤x≤1) powders were synthesized using microwave-hydrothermal method at a low temperature of 165°C/45min. The synthesized powder was characterized by using XRD, TEM, FTIR and DSC. The particle size was obtained from TEM study varies from 18nm to 34nm for all the nanopwders. DSC curve of composites shows no anatase to rutile phase transformation. As synthesized powder was densified using a microwave sintering method at 500°C/30min. In the XRD patterns of sintered composite samples, no peaks other than TiO2 and CoFe2O4 were observed. The grain sizes of the composites have been estimated from SEM pictures and they are in between 54 to 78nm. The dielectric properties were measured in the frequency range of 100 Hz to 1 MHz. The frequency variation of dielectric properties is understood with the help of Maxwell–Wagner type of interfacial polarization, which is in agreement with Koop’sphenomenological theory. The thermal variation of dielectric constant and loss studies were also undertaken at a constant frequency of 1kHz. Magnetic properties were also measured on all the composite samples at room temperature. The saturation magnetization (Ms) of the samples decreases with an increase of TiO2 content in CoFe2O4.

Structural And Impedance Spectroscopy Analysis Of Ba(Fe0.5Nb0.5)O3-BaTiO3 ceramic System 

N. K. Singh; Radheshyam Rai;Andrei L. Kholkin; Pritam Kumar

Advanced Materials Letters, 2012, Volume 3, Issue 4, Pages 315-320
DOI: 10.5185/amlett.2012.5345

Polycrystalline samples of BaFe0.5Nb0.5O3 and (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3, [referred as BFN and BFN-BT respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The formation of the compound was checked by an X-ray diffraction (XRD) technique. The microstructure analysis was done by scanning electron micrograph. The spectroscopic data presented in impedance plane show the grain and grain boundary contributions towards electrical processes in the form of semi-circular arcs. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–5MHz) and temperatures (30-282°C) showed that these properties are strongly temperature and frequency dependent.

Citrate–nitrate Derived Sr0.5Ba0.5Ta2O6 Tetragonal Tungsten Bronze Nanorods: Investigation Of Their Optical And Dielectric Properties

Yogesh Kumar Sharma; Krishna Kumar; Chandrashekhar Sharma; R. Nagarajan

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 118-125
DOI: 10.5185/amlett.2011.6278

First time novel complex strontium barium tantalate, Sr0.5Ba0.5Ta2O6 was successfully synthesized in 1D structure (nanorods) by citrate-nitrate gel route. Their structural properties were examined via X-ray diffractometry (XRD) and revealed the formation of tetragonal tungsten bronze (TTB) structure at as low as 1100ºC. Also, FT-IR, FT-Raman, UV-vis, SEM, TEM and PL were used to identify the structure and properties of powders. Well isolated nanorods of the average diameter of ~200nm can be fabricated by this route. PL spectrum showed strong and broad visible emission band around 439nm due to particles with little surface defects. The frequency dependent dielectric dispersion of SBT50 powders sintered at 1300°C/4 h was investigated in a frequency range from 1 kHz-1MHz and at different temperatures (25°C- 450°C). It is observed that: (i) the dielectric constant (ε') and loss tangent (tan δ) are dependent on frequency, (ii) the temperature of dielectric constant maximum shift toward lower temperature side and the maximum dielectric constant (ε) was observed to be 2400 at 1 kHz. The Tc was found to be ~444-449°C and ferroelectric relaxor or diffuse phase transition like behavior was observed at around 449°C.

Comparative study of structure, dielectric and electrical behavior of Ba(Fe0.5Nb0.5)O3 ceramics and their solid solutions with BaTiO3

N.K. Singh; Pritam Kumar; Radheshyam Rai

Advanced Materials Letters, 2011, Volume 2, Issue 3, Pages 200-205
DOI: 10.5185/amlett.2010.11178

Dielectric properties of (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3 (where x = 0.00, 0.05 and 0.10) solid solution ceramics at high temperature range of RT ~ 270 o C have been characterized in this paper. The above said polycrystalline ceramics with (x = 0.0, 0.05 and 0.10) have been produced via a mixed oxide route. The effects of BaTiO3 substitution on the structure and on the electrical and ferroelectric properties of Ba(Fe0.5Nb0.5)O3 samples have been studied by performing x-ray diffraction and dielectric measurements. The dielectric properties (e¢ and tan d) were investigated in the temperature range of 30-270 °C and in the frequency range of 100 Hz-5 MHz. The variation of relative dielectric permittivity (tan d) and tangent loss (tan d) has suggested a significant role of hopping of trapped charge carriers, which is resulted in an extra dielectric response in addition to the dipole response. It is observed that: (i) the relative dielectric permittivity and tangent loss (tan d) are dependent on frequency, (ii) the temperature of dielectric permittivity maximum shifts toward lower temperature side and (iii) dielectric permittivity and tangent loss rapidly increase by making solid solution of BFN with BaTiO3. X-ray diffraction analysis of the compound suggests the formation of single-phase compound with monoclinic structure. SEM photographs exhibit the uniform distribution of grains. The maximum ferroelectric transition temperature (Tc) of this system was 250-270 °C with the dielectric constant peak of 72500 at 1.09 kHz for x = 0.05.

Study of Pb(Zr0.65Ti0.35)O3(PZT(65/35) doping on structural, dielectric and conductivity properties of BaTiO3(BT) ceramics

Arun Chamola; Hemant Singh; U.C. Naithani

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 148-152
DOI: 10.5185/amlett.2010.11183

(1−x)BaTiO3–xPZT(65/35) ceramics were prepared by high temperature solid state reaction technique. Structural properties of the compounds were examined using an X-ray diffraction (XRD) technique to confirm the formation of phase at room temperature. Detailed studies of dielectric properties of (1−x) BaTiO3–xPZT(65/35) for all compositions were in temperature range 30-200 o C reveal that the compound have transition temperature well above at the room temperature. While pure BaTiO3 ceramics exhibited a sharp phase transformation expected for normal ferroelectrics, phase transformation behavior of the (1−x)BaTiO3–xPZT(65/35) solid solutions became more diffuse with increasing PZT(65/35) contents. The diffusivity of the dielectric peaks in the compound exhibited the values between 1 and 2 where the higher value indicates the greater disorder in the systems. This was primarily evidenced by an increased broadness in the dielectric peak, with a maximum peak width occurring at x = 0.5. The temperature dependence of ac conductivity indicated that the electrical conductivity decrease above Tc on increasing the PZT(65/35) contents. This increase in the conductivity is attributed to the increase in polarizability of the materials around Tc, due to oxygen vacancies.

MgCl2 added triglycine sulphate crystals

V. Krishnakumar; M. Rajaboopathi; R. Nagalakshmi

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 163-169
DOI: 10.5185/amlett.2010.12220

Single crystals of pure and MgCl2-added triglycine sulphate crystals were grown from aqueous solutions by low temperature solution growth technique. From the powder XRD technique crystal system remains same (Monoclinic) and the unit cell parameters are slightly different from the pure TGS. FTIR and FT-Raman spectra were recorded to identify the vibrational activity of the various functional groups present in the title crystals. To determine the concentration Mg 2+ ion in the MgCl2- added triglycine sulphate crystals inductively coupled plasma optical emission spectrometer (ICP-OES) study was carried out. The amount of MgCl2 (mol %) incorporated into the crystal is very low, a factor of 10 -2 in comparison to the actual amount taken in the solution. UV-VIS-NIR study shows that there is wide transparency in the visible region and the band gap energies were calculated. The mechanical strength of the grown crystals were known by hardness numbers and work hardening coefficient values. Dielectric constant and dielectric loss of the crystals were studied as function of frequency.

Structural, dielectric and electrical properties of Lead zirconate titanate and CaCu3Ti4O12 ceramic composite

Arun Chamola; Hemant Singh; U.C. Naithani; Shubhash Sharma; Uday Prabhat; Pratiksha Devi; Anuradha Malik; Alok Srivastava; R.K. Sharma

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 26-31
DOI: 10.5185/amlett.2010.12182

In the present work, structural, dielectric and electrical properties of lead zirconate titanate and CaCu3Ti4O12 ceramic composite with composition (1-x)Pb(Zr0.65Ti0.35)O3 - xCaCu3Ti4O12 (where x = 0, 0.20, 0.40 and 0.60) has been reported. The sample was prepared by employing a high-temperature solid-state reaction technique. X-ray diffraction studies confirm the formation of pure phase for x = 0.00 concentration and composite phases for the x = 0.40, 0.60 compositions. Doublet of diffraction peaks suggests structural change for x = 0.20 composition. Scanning electron micrographs show a uniform grain distribution and the grain size and shape modified upon CaCu3Ti4O12 addition. Dielectric measurement demonstrates a decrease in the dielectric constant with increase in CaCu3Ti4O12 percentage. The prepared ceramic composites have high dielectric constant and low dielectric loss. The temperature dependence of the ac conductivity indicated that the conduction process is due to singly ionized (in ferroelectric region) and doubly ionized (in paraelectric region).