Volume 5, Issue 2, February 2014


Editorial

International Conference On Smart Materials And Surfaces (SMS), Bangkok

Ashutosh Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 59-60

We are pleased to announce International Conference on Smart Materials and Surfaces (SMS). It will be organised jointly by SETCOR, IAAM and VBRI Press during 26-28 August 2014 at Sheraton Grande Sukhumvit Hotel, Bangkok, Thailand. Smart Materials and Surfaces (SMS), Bangkok is a three-day event targeting researchers interested in the design, modification, characterisation and applications of Novel Smart & Active Surfaces and Materials. The goal of conference is to provide a global platform for researchers and engineers coming from academia and industry to present their research results and activities in the field of Intelligent Materials science and engineering. The conference will provide opportunities for the delegates to exchange face-to-face their novel ideas and experiences with the international experts during plenary & invited talks, oral presentations and poster sessions. We will set up sessions with keynote forum, panel discussion, project negotiation along with welcome cocktail and gala dinner.

Grain Shape Effect On Dielectric Properties And Ionic Conductivity Of Gd-doped Ceria

S. A. Acharya; K. Singh

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 61-66
DOI: 10.5185/amlett.2013.fdm.03

Dielectric behaviour and ionic conductivity of nanostructured Ce0.9Gd0.1O2-d(GDC) are investigated to probe morphology influence of grains on ion transport mechanism at microscopic level. GDC are synthesized in two different morphologies of grains (rod-shape and round-shape particles). TEM study confirmed shape and size; diameter of rods are observed around 20 nm and length are in range of 50-100 nm, while diameter of round particles are found about 10 nm. The dielectric behaviour is studied using the dielectric functions such as dielectric permittivity (e’) and electric modulus (M”). The ionic conductivity is studied by temperature dependent impedance spectra. Both these properties are observed to be finely manipulative by morphology and size. Activation energy of charge carrier relaxation and charge carrier orientation are calculated from impedance spectra and electric modulus spectra and are found to be more in rod-shape GDC. Dielectric relaxation times are also observed to be more for GDC rods. This study provides clear evidence that grain shape and size affect on dopant-oxygen vacancies ineraction, which affect on ion migration and hence ionic conductivity. 1D morphology of grains in oxy-ion conductor has high potential to enhance ionic conductivity.

Synthesis Of (Ag0.5Fe0.5)TiO3 Nanocrystalline Powder Using Stearic Acid Gel Method

Sandeep Kumar; L. K. Sahay; Anal K. Jha; K. Prasad

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 67-70
DOI: 10.5185/amlett.2013.fdm.06

A low-cost, green and reproducible stearic acid assisted synthesis of nanocrystalline powder of (Ag0.5Fe0.5)TiO3 (n-AFT) is reported. X-ray, FTIR, energy dispersive X-ray and transmission electron microscopy analyses are performed to ascertain the formation of n-AFT. Rietveld refinement of X-ray data indicated the formation of a single-phase monoclinic structure. Individual nanoparticles almost spherical in shape having the sizes of 5-14 nm are found. The mechanism of nanotransformation for the soft-chemical synthesis of n-AFT has been explained using nucleation and growth theory. UV-visible study revealed the surface plasmon resonance at 318 nm. Dielectric study revealed a low value of dielectric constant (= 177) and dielectric loss (= 0.013) at 1 kHz. Magnetic studies have been carried out using vibration sample magnetometer, which indicated the possibility of magnetoelectric coupling.

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.

Modified Transport Properties Of LiNbO3 Dispersed Li2CO3 Composite System For Electrochemical CO2 Sensor

Prashant Ambekar; Jasmir Randhawa; Kamal Singh

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 75-79
DOI: 10.5185/amlett.2013.fdm.20

In the present investigation, LiNbO3 dispersed Li2CO3 composite of varying volume fraction is prepared. Its validity of placement in ionic conductor is verified by determining ionic transference number by Wagner’s dc polarization technique and bulk electrical conductivity is estimated with complex impedance spectroscopy. Two different conduction mechanisms are revealed by the complex impedance plots at low and high frequencies. Significant enhancement in the ionic conductivity has resulted due to enhancement in vacancies at the grain boundary interface facilitated by the localized polarization of carbonate grains due to the presence of ferroelectric phase. The effect on electrode kinetics is studied by characterizing an electrochemical CO2 gas sensor with this composite as sensing electrode which showed significant reduction in response time and recovery time (<10 sec). The use of such composite systems will benefit the development of fast electrochemical devices.

 Piezoelectric Polarization Effect And Phonon Relaxation Rates In Binary Wurtzite Nitrides

Sushant K. Sahoo; Bijay K. Sahoo; Sukadev Sahoo

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 80-83
DOI: 10.5185/amlett.2013.fdm.26

The piezoelectric (PZ) polarization property present in the wurtzite nitrides modifies the group velocity of phonons. As a result, the relaxation rates of phonons are changed. In this paper, we have calculated the relaxation rate of phonons as functions of the phonon frequency in binary wurtzite nitrides (GaN, AlN and InN) using the modified phonon group velocity. Different scattering mechanisms such as Umklapp, point defect, dislocation, boundary and phonon-electron scattering processes have been considered. The percentage change in phonon relaxation rates is found to be maximum for InN and minimum for GaN. This result can be used to study the effect of PZ polarization property on thermal conductivity of these materials.

Magnetic, Magnetocapacitance And Dielectric Properties Of BiFeO3 Nanoceramics 

B. Kumari; P. R. Mandal; T. K. Nath

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 84-88
DOI: 10.5185/amlett.2013.fdm.36

Single phase Bismuth ferrite (BiFeO3, BFO) nanoparticles (particle size ~ 50-100 nm) were synthesized by a novel chemical sol-gel technique. The detailed microstructural analysis has been performed through HRXRD, HRTEM and FESEM techniques. The nanoparticles are found to crystallize with distorted rhombohedral structure having R3c space group. The dielectric constant and tan δ loss are found to vary monotonically with temperature measured at different frequency ranging from 1 kHz to 1 MHz. The M (H) hysteresis behavior at 5 K reveals weak ferromagnetic nature of the BiFeO3 nanoparticles having coercivity (Hc) ~ 720 Oe and magnetization (Ms) ~ 1 emu/g at 5 T from SQUID measurements. The multiferroic character of BFO nanoparticles is confirmed through magnetoelectric response. The typical value of magnetodielectric response is observed to be 0.4% at 4300 Oe at room temperature at a frequency of 1 kHz. All the results suggest that the BFO nanoparticles are technologically very promising as far as magnetoelectric properties are concerned.

Dielectric Behavior Of Mixed Cadmium Magnesium Hydrogen Phosphate Crystal 

K. K. Bamzai; Rashmi Gupta; Shivani Suri; Vishal Singh

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 89-95
DOI: 10.5185/amlett.2013.fdm.41

Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X - ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker’s hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε/) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330ËšC in case of magnesium hydrogen phosphate to 310ËšC in case of cadmium magnesium hydrogen phosphate.

A Comparative Study Of Electrical Properties Of Some Rare Earth Based Tungsten Bronze Ceramics

P. S. Sahoo; B. B. Mohanty; R. N. P. Choudhary

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 96-99
DOI: 10.5185/amlett.2013.fdm.47

The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. Barium based ferroelectric materials have gained much importance due to their vast applications as they possess high dielectric constant, non-linear spontaneous polarization, negative temperature coefficient of resistance behavior etc.. All these characteristics stimulated the researchers to replace toxic and hazardous lead based materials by barium based TB materials from industry. Our present research work deals with the synthesis of polycrystalline samples of Ba2Sr3RTi3V7O30 (R = Gd, Sm) by a high temperature solid state reaction technique and a comparative study of the electrical properties of the samples. Preliminary structural (XRD) analyses of these compounds show the formation of single-phase orthorhombic structures at room temperature having average crystallite size of the order of some nanometer for both the compounds. The electrical properties for both the samples are studied in a wide range of temperature (30–500 o C) and frequency (100Hz-1MHz). The dielectric properties suggest that both the compounds have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 230 and 313 0 C for R= Sm and Gd respectively at frequency 100 kHz).The bulk resistance of the materials exhibits negative temperature coefficient of resistance behavior as observed in semiconductors.

Effective Complex Permittivity And AC Conductivity Of (Bi0.5Na0.5)0.94Ba0.06 TiO3-PVDF 0-3 Composite

Ansu Kumar Roy; K. Amar Nath; K. Prasad; Ashutosh Prasad

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 100-105
DOI: 10.5185/amlett.2013.fdm.77

The present study addresses the problem of quantitative prediction of effective complex relative permittivity and ac conductivity of (Bi0.5Na0.5)0.94Ba0.06TiO3-Polyvenylidene Fluoride (BNBT06-PVDF) 0-3 composite samples (prepared by solution cast method at an elevated temperature) having 10, 20 and 30 volume percentage of BNBT06 powder. SEM micrographs of the fractured surfaces showed that the particle distribution in the grains is not strictly homogeneous. Some areas of agglomeration of particles in the grains are also seen in the micrographs. EDAX patterns confirmed the presence of different constituent elements of the composite samples. The resulting data for room temperature real and imaginary parts of relative permittivity as well as real part of ac conductivity showed an increasing trend with increasing volume fraction of the ceramic filler. The 30 vol. % of BNBT06-PVDF composite had the highest dielectric constant of 75.3 and dielectric loss of ~6.09 i.e., loss tangent ~0.08. Among the dielectric mixing models presented, Rother-Lichtenecker model showed the best fit to the experimental data for the test composite. Similar equations for effective ac conductivity in terms of conductivity of the constituent phases of the composite were proposed in the present work to be fitted to find that none except Rother-Lichtenecker equation fitted the experimental data well. First order exponential growth type of equation applicable to all the three properties fitting the experimental data excellently is also proposed in the present work.

Electrical Properties Of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3

Jeewan Kumar; S. N. Choudhary; K. Prasad; R. N. P. Choudhary

Advanced Materials Letters, 2014, Volume 5, Issue 2, Pages 106-110
DOI: 10.5185/amlett.2013.fdm.81

The polycrystalline sample of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3 was synthesized using conventional solid state reaction technique. XRD analysis indicated the formation of a single-phase orthorhombic structure. The SEM analysis shows the grain sizes to be 0.12 to mm. Complex electric modulus analyses suggested the dielectric relaxation to be of non-Debye type. Dielectric studies indicated the relaxor behavior of 0.25Ba(Bi1/2Ta1/2)O3-0.75BaTiO3. The correlated barrier hopping model was employed to explain the mechanism of charge transport in the system. The ac conductivity is found to obey the Jonscher’s power law. The nature of variation of dc conductivity with temperature suggested NTCR behavior with activation energy 0.36eV. The studied material can be a potential candidate for capacitor applications.