George Varughese
Articles written in Bulletin of Materials Science
Volume 32 Issue 6 December 2009 pp 621-626 Single Crystals
George Varughese A Santhosh Kumar J Philip Godfrey Louis
The double sulfate family (ABSO4), where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li2Na3(SO4)2.6H2O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, 𝐶11 = 𝐶22, 𝐶33, 𝐶44 = 𝐶55, 𝐶12, 𝐶14 and 𝐶13 = 𝐶23 are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the polar plots of phase velocity, slowness, Young’s modulus and linear compressibility in 𝑎–𝑏 and 𝑎–𝑐 planes.
Volume 36 Issue 1 February 2013 pp 143-148
George Varughese A S Kumar J Philip Godfrey Louis
The double sulfate family of (ABSO4) where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li2Na3(SO4)2.6H2O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, 𝐶11 = 𝐶22, 𝐶33, 𝐶44 = 𝐶55, 𝐶12, 𝐶14 and 𝐶13 = 𝐶23, are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the surface plots of phase velocity, slowness, Young’s modulus and linear compressibility in 𝑎–𝑏 and 𝑎–𝑐 planes.
Volume 39 Issue 5 September 2016 pp 1327-1334
Detection of anomalies in NLO sulphamic acid single crystals by ultrasonic and thermal studies
The ultrasonic pulse echo overlap technique (PEO) has been used to measure the velocities of 10 MHz acoustic waves in sulphamic acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiffnessconstants, compliance constants and Poisson’s ratios of the crystal. The temperature variations of the elastic constants have been determined. The phase transition studies above room temperature were investigated using ultrasonic PEO technique. This study has suggested new weak elastic anomalies for the crystal around 330 K. The transverse elastic constants C44 and C66 have shown clear thermal hysteresis of 2 K. The present differential scanningcalorimetric (DSC) studies carried out at a slow heating rate have also suggested weak phase transition around 331 K. The present elastic and thermal studies have been substantiated by already reported DC electrical conductivitystudies around 330 K.
Volume 46, 2023
All articles
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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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