Keywords : Ferroelectric

Synthesis and characterization of pure BiFeO3 using various complexing agents by Sol-gel method

Balesh Kumar Vashisth; Jarnail S. Bangruwa; S. P. Gairola; Vivek Verma

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 805-810
DOI: 10.5185/amlett.2018.2173

Pure BiFeO3 (BFO) nanoparticles were prepared using various complexing agents like citric acid, malonic acid, succinic anhydride and tartaric acid by sol-gel method annealed at different temperatures (400 °C, 500 °C, 600 °C). X-Ray diffraction pattern of various samples show the degree of formation of required phase. Particle size of pure phase BFO has been shown using TEM image. Scanning Electron Microscopy studies for different samples give detailed study of morphology of samples. Ferroelectric and magnetic studies of best prepared samples show their comparative multiferroic properties. Dielectric analysis also shows the variation in dielectric loss, real and imaginary part of permittivity versus frequency at room temperature.

Effect of heating rate on microstructure and electrical properties of microwave sintered CaCu3Ti4O12 ceramics

Sandeep Kumar; Neetu Ahlawat; Navneet Ahlawat

Advanced Materials Letters, 2017, Volume 8, Issue 5, Pages 605-613
DOI: 10.5185/amlett.2017.6398

In the present work, the results of microstructure, dielectric and ferroelectric investigation of microwave sintered CaCu3Ti4O12 (CCTO) ceramic with different heating rate are presented. Scanning electron micrographs revealed that grain size decreases from 1.167 µm to 0.744 µm with increased heating rate from 10ºC/min. to 50ºC/min which can be explained on the basis of phenomenological kinetic equation for grain growth. Dielectric response also found to influence by heating rate. The CCTO ceramic sintered with 50 ºC/min. exhibited highest dielectric constant (ɛr~3915) with nominal losses (0.10) at room temperature in broad frequency range from 10 2 Hz-10 5 Hz. Cole-Cole plots revealed the change in grain boundary resistivity mainly caused by the oxygen vacancy activities and affected by varying sintering heating rate. An anomaly observed for 50 ºC/min heating rate due to trapping of oxygen at grain boundaries. The remnant polarization and coercive field for CCTO ceramic sintered with 50ºC/min were 0.1 µC /cm 2 and 1.477 kV /cm respectively. Remnant polarization found to decrease while the coercive field increases with increasing heating rate applying these are micro-structural dependent.    

Nano-textured Pb (Zr0.52Ti0.48)O3/ZnO Hetero-structure On Silicon Substrate   

Govind N. Sharma; Shankar Dutta; Ratnamala Chatterjee; Sushil Kumar Singh

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 951-956
DOI: 10.5185/amlett.2016.6509

Metal oxide based hetero-structures (like Pb (ZrxTi1-x) O3 – ZnO) can be used for wide variety of future sensors and electronic devices. This paper presents growth and electrical properties of nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (001) ZnO hetrostructure on oxidized silicon substrate by RF sputtering technique. The grain sizes of ZnO and PZT films are found to be around 30 nm and 80 nm respectively. Resistivity of the ZnO layer is found to be 1x10 9 ?-cm. The electrical properties of the film are studied by creating in-plane electrodes on top of the PZT/ZnO hetrostructure film. The remnant polarization of the film is found ~ 47 µC/ cm 2 at 200 kV/ cm 2 . Dielectric constant of the film is found to be 300 at 1 kHz. The film also showed a low leakage current density of ~ 10 -5 A/cm 2 at 200 kV/ cm applied electric field. The nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (100) ZnO hetrostructure integrated with inter-digital-transducers and microelectronic is well suitable for low-cost, robust, programmable passive micro sensors for military structure and systems such as aircraft, missiles.

Structural, Dielectric, Magnetic And Magnetoelectric Characterization Of Co0.5Ni0.5Fe2O4 - Bi0.9La0.1FeO3 Composite

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

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 853-861
DOI: 10.5185/amlett.2015.5856

Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 ºC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 and rhombohedral perovskite Bi0.9La0.1FeO3 ceramics. FESEM micrographs show closely packed microstructure with grain size in the range 503 nm - 960 nm. Variation of dielectric constant and dielectric loss with temperature at two fixed frequencies (500 kHz and 1 MHz) was studied. The composite with composition x = 0.55/sintered at 850 ºC exhibits the largest coercitivity (Hc) of 883 Oe. The saturation magnetization (Ms) and magnetic moment (µB) increase with an increase of Co0.5Ni0.5Fe2O4 concentration in the composites. From ferroelectric hysteresis loop analysis the values of remnant polarization (Pr) and coercive field (Ec) was found to lie in the range of 0.018-0.745 µC/cm 2 and 3.89-6.06 kV/cm. The relative change of magnetocapacitance was found to be 6.6% at a magnetic field of 8 kOe for x = 0.55 composition. Impedance analysis suggests the presence of a temperature dependent electrical relaxation in the material having a typical negative temperature coefficient of the resistance (NTCR) behavior analogous to a semiconductor.

Phase Transitions Of The Ferroelectric Na0.5Bi0.5TiO3 By Dielectric And Internal Friction Measurements

Venkata Ramana Mudinepalli; N. Ramamanohar Reddy; Wen-Chin Lin; K.V. Siva Kumar; B.S. Murty

Advanced Materials Letters, 2015, Volume 6, Issue 1, Pages 27-32
DOI: 10.5185/amlett.2015.5620

This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as a function of temperature. A sequence of phase transitions has been studied by both dielectric and anelastic measurements. Three internal friction peaks were observed near 350, 200 and 120 °C. The 350 °C-peak corresponds to a transition associated with the tetragonal (P < /em>4bm) to rhombohedral (R3c) phase, and the 200 °C-peak is related to the ferroelectric to antiferroelectric phase transition. The 120 °C-peak could be ascribed to the interaction between the domain walls and the diffusion of oxygen vacancies in the domains.

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.

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). 

Ferrolectric Nanofibers: Principle, Processing And Applications

Seema Sharma

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 522-533
DOI: 10.5185/amlett.2012.9426

Nanotechnology is one of the rapidly growing scientific disciplines due to its enormous potential in creating novel materials that have advanced applications. Electrospinning has been found to be a viable technique to produce materials in nanofiber form. Ferroelectric and/or piezoelectric materials in nanofiber and/or nanowire form have been utilized for producing energy harvesting devices, high frequency transducers, implanted biosensors, vibration absorbers and composite force sensors, etc. An in-depth review of research activities on the development of ferroelectric nanofibers, fundamental understanding of the electrospinning process, and properties of nanostructured fibrous materials and their applications is provided in this article. A detailed account on the type of fibers that have been electrospun and their characteristics is also elaborated. It is hoped that the overview article will serve as a good reference tool for nanoscience researchers in ferroelectric materials.