G. Nag Bhargavi

Bio: G. Nag Bhargavi is an academic researcher from National Institute of Technology, Raipur. The author has contributed to research in topics: Ceramic & Dielectric. The author has an hindex of 6, co-authored 11 publications receiving 81 citations.

Luminescence studies of perovskite structured titanates: A review

Abstract: Apart from widely known dielectric and ferroelectric properties, the perovskite type materials also constitute a class of materials, which are recently investigated for their optical properties. These materials are being used for fabrication of various microelectronics and optoelectronic devices. Photoluminescence (PL), mechanoluminescence (ML) and thermoluminescence (TL) are such phenomena offering numerous applications in different fields like electro-optics, flat panel displays, LED technology, sensors, dynamic visualization etc. This paper briefly reviews the status and new progress in luminescence studies of ferroelectric materials like barium titanate (BT), barium zirconate titanate (BZT), calcium titanate (CT), calcium zirconate titanate (CZT), lead titanate (PT), lead zirconate titanate (PZT), etc., prepared through various methods.

Electrical characterizations of BaZr0.05Ti0.95O3 perovskite ceramic by impedance spectroscopy, electric modulus and conductivity

Abstract: We, here in report on the impedance, modulus and conductivity analyses of polycrystalline perovskite structured BaZr0.05Ti0.95O3 ceramic prepared by the conventional solid state reaction technique (SSRT). The X-ray diffraction (XRD) pattern of the specimen confirms the formation of phase pure perovskite structure. The surface morphology of the sample investigated by scanning electron microscopy (SEM) reveals closed packing of grains having good density and very less porosity. Impedance spectroscopy, electric modulus and conductivity have been used as a tool to investigate the electrical conduction mechanism occurring within the material. These studies are performed as a function of both temperature and frequency. The sample has been observed to exhibit negative temperature coefficient of resistance (NTCR) behavior indicating its semiconducting character. The Cole–Cole plots indicate the presence of both grains and grain boundaries. The various relaxation times in the electric modulus studies indicate that the material does not follow Debye law. The conductivity variation of BaZr0.05Ti0.95O3 ceramic has also been reported as a function of temperature.

Analysis of temperature and frequency dependent dielectric properties, dynamic hysteresis loop and thermal energy conversion in BaZr0.05Ti0.95O3 ceramic

Abstract: The barium zirconium titanate ceramic with formula BaZr0.05Ti0.95O3 has been synthesized by the conventional solid state reaction technique. The synthesized ceramic sample is characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, temperature dependent dielectric spectroscopy and ferroelectric behaviour. The Raman spectrum confirms the orthorhombic structure at room temperature and local distortions due to distorted octahedral structures. The temperature dependent dielectric study reveals the occurrence of three transition temperatures representing rhombohedra to orthorhombic, orthorhombic to tetragonal and tetragonal to cubic transition in the material. The area of the hysteresis loop decreases with temperature up to the transition temperature, followed by an increase at higher temperatures. Scaling relations for coercive field (Ec) and remnant polarization (Pr) are studied as a function of temperature. This exhibits back-switching polarization behaviour as a function of temperature. The thermal energy conversion potential of the studied sample is obtained by using Olsen cycle.

Investigation of structural and electrical properties of Gd 3+ ions modified BaZr 0.05 Ti 0.95 O 3 ceramic

Abstract: Gadolinium (Gd) doped BaZr0.05Ti0.95O3 ceramic samples with general formula Ba(1−x)Gd2x/3Zr0.05Ti0.95O3 were prepared by the solid state reaction method. The effect of Gd on the structural and dielectric behaviours of BaZr0.05Ti0.95O3 have been studied in detail. X-ray diffraction studies revealed that site substitution by Gd3+ ions had a great impact on the site occupancy of the BaZr0.05Ti0.95O3 pervoskite. The lattice parameters increased up to x = 0.03 followed by a decrease at higher concentration showing both donor and acceptor behaviours of Gd in BaZr0.05Ti0.95O3 matrix. Structural changes were studied by Raman spectroscopy also, which showed the non-linear shifting of the modes with increasing doping concentration. The scanning electron microscopy images showed a drastic modification in grain size with increasing Gd concentration. The effect of substitution of Gd3+ ions in BaZr0.05Ti0.95O3 was investigated by means of dielectric studies and the dielectric behaviour was explained using self-compensation model. The diffusivity in the samples was studied by modified Curie–Weiss law.