Magnetoelectric and Multiferroic Properties of BaTiO3/NiFe2O4/BaTiO3 Heterostructured Thin Films Grown by Pulsed Laser Deposition Technique

Development of lead-free BaTiO3/NiFe2O4/BaTiO3 (BTO/NFO/BTO) trilayer structure thin films is significant for the realization of eco-friendly and implantable microelectromechanical systems (MEMS)-based devices. In the present work, we report BTO/NFO/BTO trilayer structure as a representative ferroelectric/ferromagnetic/ferroelectric (FE/FM/FE) system deposited on Pt(111)/TiO2/SiO2/Si using Pulsed Laser Deposition (PLD) technique. We report the ferroelectric, magnetic, and ME properties of BTO/NFO/BTO trilayer nanoscale heterostructure having dimensions 140/80/140 nm, at room temperature. High room temperature dielectric constant ~2145 at 100 Hz with low dielectric loss ~0.05 at 1 MHz is observed. Further, the deposited (BTO/NFO/BTO) tri-layered thin films showed magnetoelectric, multiferroic behavior with remanent polarization of 8.63 μCcm−2 at about 0.25 MV/cm and a reasonably high saturation magnetization of ~16 emu/cm3 at ~10 kOe is witnessed at room temperature. Tri-layered films have shown interesting magnetoelectric (ME) coupling coefficient (αE) ~54.5 mV/cm Oe at room temperature.

Influence of CuO Additive on Density and Dielectric Properties of Ba(Zr0.05Ti0.95)O3 Ceramics Prepared by Molten Salt Method

In this research, the Ba(Zr0.05Ti0.95)O3 powders were prepared by molten salt method. The powders were calcined at 600-1100°C for 3 h with heating rate of 5°C/min. The BZT powders were synthesized by molten salt method to reduce the calcination temperature by up to 300°C. The sintering procedure was carried out at 1250°C for 2 h with a heating/cooling rate of 5°C/min. Phase formation and microstructure were examined by XRD and SEM, respectively. The influence of the CuO additive on density and dielectric properties were investigated. The density of the sintered samples was measured by Archimedes method with distilled water as the fluid medium. Dielectric properties were examined by LCR meter. The BZT+2.0 mol% CuO ceramic sintered at 1250°C showed the highest density of 5.76 g/cm3, and the room temperature dielectric constant and dielectric loss at 1 kHz were 2687 and 0.01, respectively.

Bi2O3-Modified Ceramics Based on BaTiO3 Powder Synthesized in Water Vapor

Bi2O3 was investigated in the role of a modifier for BaTiO3 powder synthesized in a water vapor atmosphere at 200 °C and 1.55 MPa. Modification was aimed at increasing the sinterability of the powder as well as improving the structural and dielectric properties of the obtained ceramics. The morphology and phase contents of the synthesized BaTiO3 powder were controlled by the methods of SEM and XRD. Properties of pure and Bi-doped BaTiO3 ceramics were comprehensively studied by XRD, SEM, dielectric spectroscopy, and standard approaches for density and mechanical strength determination. Doping with Bi2O3 favored BaTiO3 ceramic densification and strengthening. The room-temperature dielectric constant and the loss tangent of Bi-doped BaTiO3 were shown to stabilize within the frequency range of 20 Hz to 2 MHz compared to non-doped material. The drop of dielectric constant between room temperature and Curie point was significantly reduced after Bi2O3 addition to BaTiO3. Bi2O3 appeared to be an effective modifier for BaTiO3 ceramics produced from non-stoichiometric powder synthesized in water vapor.

AC CONDUCTIVITY AND DIELECTRIC STUDIES OF POLYPYRROLE-PAPAIN COMPOSITE

Enzyme doped polypyrrole polymer were synthesized by in situ polymerization where ferric chloride works as an oxidizing agent. The different weight percent of papain was added at the time of polymerization. The polypyrrole-papain composite of various composition was analyzed for its dielectric and a. c. conductivity by using LCR meter at room temperature. Dielectric constant and loss decreases, with escalation in frequency. The variation in dielectric constant and dielectric loss was also noted with change in papain percentage in pyrrole.

Influence of sintering technique on the characteristics of Li–Co nanoferrites

Li–Co nanoferrites (Li[Formula: see text]Co[Formula: see text]Fe[Formula: see text]O4) with x = 0.00, 0.03, 0.06, 0.09, and 0.12, were synthesized by chemical sol–gel method. Two different sintering techniques viz. conventional technique (CT) and microwave technique (MT) were employed to heat treat the synthesized samples with an aim to study the effect of sintering technique on the properties of the nanoferrites. Structural and microstructural properties of the samples were investigated using XRD and scanning electron microscopy (SEM) technique, respectively. The variation of room temperature dielectric constant and dielectric loss were measured as a function of frequency in the range 100 Hz–1 MHz and the normal dispersive behavior was observed. Magnetic properties were investigated using Vibrating Sample Magnetometer (VSM), while Soohoo’s method was used to measure Curie temperature. The results obtained have been discussed in the paper.

Effect of Sintering Time on Dielectric Properties of Barium Titanate and Nb Doped Barium Titanate

Barium titanate (BaTiO3) with its perovskite structure is a promising dielectric material for many applications such as transducers, actuators, high-k dielectrics and multilayer ceramic capacitors (MLCC). In this study, we have investigated the effect of sintering time on dielectric properties of BaTiO3 and Nb-doped BaTiO3. BaTiO3 was doped with 0.3 mol % niobium oxide (Nb2O5). At first, nanosized pure BaTiO3 and Nb2O5 doped BaTiO3 were milled, dried and pressed into pellets to prepare green samples. Then, the samples were sintered at 1275°C for different time periods ranging from 2 to 5 hrs. Single stage sintering was adopted for the densification of prepared samples. Microstructure of the sintered samples was investigated employing Field-emission scanning electron microscope (FESEM). Dielectric properties of the samples were measured using an impedance analyzer. Finally, a correlation was established between the dielectric properties of the sintered samples and their microstructure. Nb has shown to provide strong inhibiting effect after sintering the samples in the range of 2 to 5 hours at 1275°C thereby, resulted in higher dielectric properties of doped BaTiO3 ceramics compared to that of pure BaTiO3. The best room temperature dielectric constant of 7200 was obtained for Nb doped BaTiO3 sintered at 1275°C for five hours. Such improved dielectric constant is attributed to the optimum grain size of about 1 micron at this sintering temperature.

Lattice strain driven dielectric insulation response of Sr1−xCaxBi2Nb2O9 ceramics

In this paper, effects of lattice strain on dielectric properties of Sr[Formula: see text]CaxBi2Nb2O9 ([Formula: see text]–0.5 in steps of 0.1) ceramics are reported. High frequency dipolar polarization is observed to increase for 10% calcium addition and suppresses thereafter on higher calcium concentrations. The dielectric loss values for all doped samples were lower compared to undoped one at frequencies beyond 1[Formula: see text]kHz. The sample with [Formula: see text] shows room temperature dielectric constant in the range (130[Formula: see text][Formula: see text][Formula: see text]12) over a wide frequency range from 50[Formula: see text]Hz to 1[Formula: see text]MHz also minimum dielectric loss among all other sample for the same frequency range. Remarkable increase in Curie temperature ([Formula: see text]) by 50[Formula: see text]C is recorded in the present work by increasing 10% calcium content in SBN compostion. All higher doped samples indicate increase in [Formula: see text] by further higher amount. In addition, dc conductivity of all samples is measured for all samples and increase in calcium content is observed to generate more insulating compositions compared to undoped SBN with higher intrinsic activation energies.

Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

Ca2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

Effect of Sintering Parameters and Ta2O5 Doping on the Microstructure and Dielectric Properties of BaTiO3 Based Ceramics

The main focus of the research was to correlate the composition and sintering parameters with the microstructure and dielectric properties of Ta2O5 (Tantalum Oxide) doped BaTiO3 (Barium Titanate) ceramics. Ta2O5 was doped at three different percentages viz. 0.5, 1.0 and 1.5 mole%. The doped samples were then sintered using both single and double stage sintering techniques. Thereafter field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) techniques were used to examine the structure of the samples with particular focus on the incorporation of Ta5+ions into the BaTiO3 crystal lattice. Finally, the dielectric properties were analyzed using impedence analyzer and the relationship between the properties and structure of doped BaTiO3 was established. From the research, it can be stated that double stage sintering yielded best dielectric properties. The best stable value of room temperature dielectric constant (k) of 19000 was obtained for 1.5mole % Ta2O5 doped BaTiO3 sample, sintered at 1320°C for 0 hour and 1280°C for 6 hours due to the combination of high percent theoretical density (%TD) and optimum grain size. At a temperature range of 30°C to 60°C, this combination of composition and sintering parameters yielded dielectric constant in the range of 18000-19000.

Investigation of Low Temperature Sintering of Low Voltage Varistor Based on TiO2

Low temperature sintering of TiO2-base varistor was systematically investigated through doing with V2O5 and B-Si glass. Pellets prepared could be densely sintered from 1273 to 1473K. The highest relative density, 94.6%, was found in the sample sintered at 1433K. According to I-V plots of ceramic pellets, the nonlinear coefficient α and breakdown voltage V1mA were obtained and found to be α=2~5 and V1mA=15~30V. The room temperature dielectric constant was very large, high as to about 20000. Powder XRD analysis has shown the desirable macro-structural characteristics of these compacts.