G S Kumar
Articles written in Bulletin of Materials Science
Volume 17 Issue 6 November 1994 pp 951-958
Studies on electrical conduction in Bi4SrTi4O15
A R James G S Kumar T Bhimasankaram S V Suryanarayana
The ferroelectric Bi4SrTi4O15 has been synthesized and a study of the electrical (AC) conductivity was made on both poled and unpoled samples in the frequency range from 100 Hz to 1 MHz and from room temperature to 550°C. In the case of unpoled samples the activation energy was found to be 0·54 eV and subsequent to poling it was lowered to 0·39 eV indicating an increased conductivity after poling. Further the conductivity increased with increasing frequency and temperature. DC conductivity measurements were also carried out. Dielectric measurements indicate a peak in the dielectric constant at 530°C.
Volume 18 Issue 1 February 1995 pp 93-97 Seminar On “Recent Trends In Glass And Glass-Ceramics Research”
Dielectric measurements in vanadium doped barium titanate
A Hanumaiah T Bhimasankaram S V Suryanarayana G S Kumar
Ceramic samples of Li0·1Ba0·95(V
Volume 19 Issue 4 August 1996 pp 639-643
Dielectric properties of cobalt doped cadmium oxalate crystals
N V Prasad G Prasad T Bhimasankaram S V Suryanarayana G S Kumar
Co
Volume 21 Issue 3 June 1998 pp 251-255
An experimental setup for dynamic measurement of magnetoelectric effect
M Mahesh Kumar A Srinivas S V Suryanarayana G S Kumar T Bhimasankaram
An experimental setup is developed for the measurement of dynamic magnetoelectric effect (ME) in polycrystalline materials, using a time varying DC magnetic field on which an AC magnetic field is superimposed. The experimental data on ME on Bi5FeTi3O15 and a solid solution of (90%)BiFeO3-(10%)BaTiO3 are obtained using this setup. The linear and higher order ME coefficients can be evaluated from the output voltage. The temperature variation of ME data gives additional information corroborating with the data on magnetization.
Volume 22 Issue 1 February 1999 pp 59-64 Electrical Properties
P S Rama Sastry G S Kumar T Bhimasankaram G Prasad
Pyroelectric properties of bismuth layer structured calcium substituted sodium bismuth titanate (Na0·5Bi0·5)1−
Volume 22 Issue 4 June 1999 pp 779-783 Electrical Properties
Electrical properties of SiO2-doped sodium metavanadate sintered discs
B V Bahuguna Saradhi G Prasad G S Kumar T Bhimasankaram
Impedance of sintered discs of 0·1, 0·25, 0·4 mol% of sodium metavanadate was measured in the frequency range 10 kHz-1 MHz and in the temperature region from room temperature (=30°C) to 450°C. AC conductivity was calculated from the data. DC conductivity was measured in the temperature range 150–450°C. Debye type of relaxation effects were observed in the dielectric loss. The activation energy of the dipoles involved in relaxation was estimated. The activation energy for AC conduction in the temperature above 380°C was calculated. These values are larger than the activation energy of pure sodium metavanadate sample. The relaxation phenomenon observed is explained.
Volume 42 Issue 1 February 2019 Article ID 0030
S MAHBOOB RIZWANA G PRASAD G S KUMAR
Dielectric, conductivity and piezoelectric properties have been studied on (Ba$_{0.997}$Nd$_{0.003}$)TiO$_3$ ceramic samples prepared through microwave sintered (MWS) and conventional sintered (CS) routes and the results are presented in this paper. The room temperature dielectric constant at 10 kHz for CS and MWS samples are 1245 and 5250 respectively. Roomtemperature dielectric constant in MWS sample was almost four times higher than that of the CS sample. The value of $K_t$ is found to be 0.998 and 0.997; whereas the value of $d_{33}$ is 7.72 nm V$^{−1}$ (573 K) and 444.66 nm V$^{−1}$ (573 K) for CS and MWS samples, respectively. In the present study almost 57 times enhancement in piezoelectric charge constant ($d_{33}$) isobserved for the MWS Ba$_{0.997}$Nd$_{0.003}$TiO$_3$ ceramic when compared to the CS ceramic.
Volume 42 Issue 2 April 2019 Article ID 0056
S MAHBOOB RIZWANA G PRASAD G S KUMAR
Dielectric data of new [Ba(Nd$_x$ Ti$1−2xNbx )O$_3$]$_{0.30}$[Na$_{0.5}$Bi$_{0.5}$TiO$_3$]$_{0.70} ($x = 0.075$) relaxor ceramic was modelled using a new modified Lorentz equation ($T$ and $\omega$ simultaneously) as proposed by us. The activation energy forthermally activated orientation of dipoles and relaxation times were estimated. Dielectric resonance and anti-resonance data as a function of temperature and angular frequency of other piezoelectric compound [Ba(Nd$_{0.1}$Ti$_{0.8}$Nb$_{0.1}$)O$_3$]$_{0.35}$ [(Na$_{0.5}$Bi$_{0.5}$)TiO$_{3}$]$_{0.65}$ was also modelled using the modified Lorentz equation as proposed by us. It is shown that using thisequation, it is possible to obtain the polarizability, piezoelectric charge constant, piezoelectric voltage constant and activationenergy for resonance and anti-resonance.
Volume 42 Issue 3 June 2019 Article ID 0114
Dielectric studies on Sm-modified two-layered BLSF ceramics
MD ABDUL BASHEER G PRASAD G S KUMAR N V PRASAD
Sm$_x$Bi$_{3−x}$TiNbO$_9$ (SBTN) with $x = 0$, 0.2, 0.4, 0.6, 0.8 and 1.0, a novel type of ceramic was prepared by a conventional solid-state reaction method. X-ray diffraction patterns confirm the formation of a single-phase, and lattice parameters were calculated based on the parent compound Bi$_3$TiNbO$_9$ (BTN). Well-defined grains were seen in the scanningelectron microscopy pictures. A kink observed near 400$^{\circ}$C for all the samples in the dielectric plot as well as in the stretched exponential parameter ($\beta$)
Volume 46, 2023
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Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
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