K B R Varma
Articles written in Bulletin of Materials Science
Volume 3 Issue 3 November 1981 pp 307-315
Growth and electro-optic studies in mixed (NH4)
K B R Varma Kolluri V Ramanaiah
Single crystals and mixed crystals of KH2PO4 (KDP) and NH4H2PO4 (ADP) were grown with different dopant concentrations of NH4H2PO4 in KH2PO4 in solution by Holden’s rotary crystallizer technique. The effect of additives like Borax (Na2B4O7·10H2O), seed crystal rotation rate and qualities of the crystals were studied. The half-wave voltages (in longitudinal mode) for KDP mixed with 1% ADP (by weight) were found and hence the unclamped (low frequency) electro-optic coefficients (
Volume 5 Issue 2 June 1983 pp 147-152
Dispersion of photoelastic constants in doped KDP crystals
The photoelastic behaviour of
Volume 9 Issue 1 March 1987 pp 1-5
Twin roller quenching technique and preparation of glasses of high melting ionic solids
A rapid quenching technique with a quenching rate of roughly 106°C/sec has been developed to prepare glassy samples of ABO3 type materials. Glasses of potassium lithium niobate have been prepared by this technique. These glasses have been characterized by x-ray diffraction, electron diffraction and differential scanning calorimetry techniques to assess the quality of the obtained glasses.
Volume 18 Issue 5 September 1995 pp 631-636 Rapid Communication
Structural and dielectric properties of a novel Bi2O3-(1 −
Vandana Sharma K B R Varma A K Shukla
A novel solid solution in the system Bi-W-Cu-O has been synthesized and its structural and dielectric properties studied. The solid solution Bi2O3-(1 −
Volume 18 Issue 7 November 1995 pp 931-936
SrB4O7:Bi2VO5·5 — A novel nanocomposite
M V Shankar G N Subbanna K B R Varma
Glass composites of strontium tetraborate, SrB4O7(SBO) with bismuth vanadate, Bi2VO5·5 (BiV) of the composition (1 −
Volume 19 Issue 5 October 1996 pp 791-798
Large single crystals of an organic nonlinear optical (NLO) material, benzil, have been grown by employing an indigenously built Bridgman-Stockbarger crystal grwoth system. The dielectric constant (
Volume 21 Issue 6 December 1998 pp 499-502 Rapid Communication
Influence of inherent strain on the curie temperature of rare earth ion-doped bismuth vanadate
K Sooryanarayana T N Guru Row R Somashekar K B R Varma
X-ray line broadening is found to be an effective parameter to estimate the strain associated with rare earth ion (Gd3+)-doped polycrystalline bismuth vanadate(Bi2VO5·5). The strain increases with increasing Gd3+ concentration. It is anisotropic and found to be maximum in (111) plane. The Curie temperature which is known to decrease with increase in the rare earth ion concentration in these compounds is correlated with increase in strain.
Volume 39 Issue 2 April 2016 pp 593-601
Magnetic and ferroelectric characteristics of Gd$^{3+}$ and Ti$^{4+}$ co-doped BiFeO$_3$ ceramics
SHIVANAND MADOLAPPA A V ANUPAMA P W JASCHIN K B R VARMA B SAHOO
Polycrystalline BiFeO3 and Bi$_{0.9}$Gd$_{0.1}$Fe$_{1−x}$Ti$_x$O$_3$ ($x = 0$, 0.01, 0.05 and 0.1) samples were synthesized by solid-state reaction route. Structural, magnetic and ferroelectric properties of these samples were investigated. X-ray powder diffraction (XRD) results confirmed the presence of a significant amount of Bi$_2$Fe$_4$O$_9$ impurity phase in the undoped BiFeO$_3$ sample. Mössbauer spectroscopy studies corroborated the XRD studies to confirm the presence of impurity phase.We have observed that gadolinium (Gd$^{3+}$) and titanium (Ti$^{4+}$) doping, respectively, on Bi$^{3+}$ and Fe$^{3+}$ sites facilitated a significant reduction in the impurity phase formation in BiFeO$_3$. Interestingly, Gd$^{3+}$-doping significantly reduced the impurity phase formation as compared to the undoped BiFeO$_3$ sample. This impurity phase formation was further overcome by doping higher ($x \ge 0.05$) amounts of Ti in BiFeO$_3$. The crystallographicsite occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data,Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectricproperties have been observed after co-doping. There was an increasing trend in remnant polarization (Pr) with the increase in Ti concentration besides an improvement in the characteristic saturation magnetization. Our resultsdemonstrate that Gd$^{3+}$ and Ti$^{4+}$ doping could be used to enhance multifunctional properties of BiFeO3 ceramics to enable them as potential material for various devices.
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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