Jayant Kolte

Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles (d ≈10 nm). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ∼1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher’s power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (∼180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impeda...

Structural and Electrical Characterization of La and Mn Co-Substituted Bismuth Ferrite Thin Films

Bismuth ferrite thin films with 10% La and 5% Mn (BLFMO) have been deposited using Pulsed laser deposition. It is found that oxygen pressure has pronounced effect on the structural and electrical properties of BLFMO thin films. The leakage current density increases with the oxygen pressure. At 0.007 mbar, the leakage current density is found to be in the order of 10−7A/cm2 at 200 kV/cm. The remnant polarization is 73 μC/cm2 at 200 kV/cm. Fatigue endurance has been studied for optimized film and found that films are almost fatigue free after 108 pulses. There is only 3% change in the polarization up to 106 seconds as revealed by retention test.

Growth and Characterization of Na0.5Bi0.5TiO3 Thin Films with BaTiO3 Buffer Layer (Study of Au/Na0.5Bi0.5TiO3/BaTiO3/Pt Capacitor)

Lead free bilayer capacitor structure has been fabricated as a combination of sodium bismuth titanate (Na0.5Bi0.5)TiO3 (NBT) thin films with barium titanate, (BaTiO3) (BT) buffer layer in situ using pulsed laser deposition (PLD). PLD control parameters have been optimized using Taguchi approach to obtain good quality NBT and BT thin films. It has been observed that dielectric properties of NBT thin films enhanced by inserting BT buffer layer. This improvement in the dielectric properties of NBT thin films have been discussed in relation to the effect of the buffer layer on the structure, microstructure and interface of the NBT/BT multilayer capacitor.

Microstructural Characterization of Ferroelectric Bismuth Ferrite (BiFeO3) Ceramic by Electron Backscattered Diffraction

Ferroelectric BiFeO3 (BFO) is potential candidate for future generation of FeRAM due to its large polarization. However, BFO is very sensitive to secondary phase formation during synthesis because of volatility issues related to Bismuth. Investigation of the microstructure for phase purity is the key as impurities can destroy the desired properties. We have used backscattered electron diffraction to study the microstructure of BFO ceramic. The EBSD results provide a direct evidence of the appearance of secondary phase that XRD could not be detected in XRD.

Structural and Magnetic properties of lithium ferrite substituted BaTi0.9Zr0.1O3 composite ceramics

Abstract Improvement of magnetic properties, suggesting the effectiveness of Li0.5Fe2.5O4 (LF) in lower concentration doped in BaTi0.9Zr0.1O3 (BTZr). The composites with a formula of (1-x)BaTi0.9Zr0.1O3 + (x) Li0.5Fe2.5O4 (x = 0.0, 0.05, 0.10 and 0.15) synthesized by conventional solid state reaction method at 1150 °C. X-ray diffraction (XRD) peaks are indexed to the crystal planes for tetragonal perovskite and spinel ferrite observed in the samples. SEM micrographs show dense microstructure resulting in increasing grain size with an increase in ferrite content. Stability of magnetic phase in the higher temperature range, enhancing the Curie temperature with increase in ferrite content.

Effect of Cobalt substitution on the structural, electrical and magnetic properties of BaTiO 3 ceramics

Cobalt doped BaTiO3 (BaTi1-xCoxO3) with x = 0, 5, 7.5, 10% have been synthesized by solid state reaction method and their structural, electrical and magnetic properties have been investigated. Structural characterization show that a multiphase ceramic containing both tetragonal and hexagonal structures are obtained for Co compositions from x = 5% to x = 10%. Ferroelectric and ferromagnetic properties have been observed in all the Co-doped BaTiO3 ceramics at room temperature. The ferromagnetic hysteresis loop at room temperature is due to the formation of oxygen vacancies and their associated exchange interaction. The saturation magnetization (Ms) was 0.010 emu/g for x = 5%. Further, at x = 7.5%, it decreases and again start increasing upto ~ 0.013 emu/g for x = 10% with Cobalt concentration. However, ferroelectric hysteresis loop (P-E) is deteriorated (lossy type) with the increase of Co concentration above x = 5%. The dielectric characterization with frequency has also been carried out for all samples. The dielectric constant decreases with increasing Cobalt concentration.

Effect of Barium Titanate buffer layer on dielectric properties of Sodium Bismuth Titanate thin films grown using Pulsed Laser Deposition

Lead free bilayer capacitor structure has been fabricated as a combination of Sodium Bismuth Titanate, (Na0.5Bi0.5)TiO3 (NBT) thin films with Barium Titanate, (BaTiO3) (BT) buffer layer in situ using Pulsed Laser Deposition (PLD). PLD control parameters have been optimized using Taguchi approach to obtain good quality NBT and BT thin films. In order to understand the effect of buffer layer on the structural and dielectric properties of NBT thin films, 50 nm thickness of BT buffer layer has been grown on Pt coated Si substrate. It has been found that dielectric constant and dielectric loss of NBT thin films is 735 and 0.07 at 1 kHz respectively. It is observed that dielectric properties of NBT thin films enhanced by inserting BT buffer layer. This improvement in the dielectric properties of NBT thin films have been discussed in relation to the effect of the buffer layer on the structure, microstructure and interface of the NBT/BT bilayer capacitor.

Effect of oxygen pressure on the structural, electrical properties of Bi0.90La0.10Fe0.95Mn0.05O3 thin films and characterization for memory applications

Bismuth ferrite (BiFeO3) is a potential candidate for future generation of FeRAM due to its large polarization with additional advantage of being lead free. La and Mn doped BiFeO3 (BLFMO) thin films were deposited by pulsed laser deposition. Effect of oxygen partial pressure on the structural and fatigue properties were studied. It has been found that polarization of thin film is very sensitive to the oxygen partial pressure. The leakage current density found to be in the order of 10-7 A/cm2 at 200kV/cm. Ferroelectric polarization is 73 μC/cm2 and coercive field is 200kV/cm. Fatigue endurance test of BLFMO thin film at 500kV/cm shows films almost fatigue free after 108 pulses. Retention test also carried out and found that there is only 3% change in the polarization up to 105 seconds, thereby making BFO a promising candidate for memory applications.