International Journal of Modern Physics B Vol. 21, No. 11 (2007) 1915–1922 c  World Scientific Publishing Company THERMAL EXPANSION STUDY OF A UVAROVITE RICH GARNET G. PARTHASARTHY and R. SRINIVASAN National Geophysical Research Institute, Hyderabad – 500007, India G. D. MUKHERJEE High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India C. BANSAL School of Physics, University of Hyderabad, Hyderabad 500 046, India ASHOK CHATTERJEE ∗ Department of Physics, Bilkent University, 06800 Bilkent, Ankara, Turkey ∗ ashok@fen.bilkent.edu.tr Received 9 May 2006 Thermal expansion measurements have been performed on a uvarovite rich garnet sample for the first time and compared with the expansion data on grossular and pyrope-rich garnets reported in the literature. A semiclassical model has been used to analyze the data and to obtain various thermodynamic parameters. Using these parameters, the lattice specific heat and the corresponding entropy have also been calculated. Keywords : Uvarovite garnets; thermal expansion. 1. Introduction Garnets are common minerals of metamorphic rocks and the upper mantle peri- dodites, 1 and are probably also important phases in the mantle-transition zone (420-670 km) depth. A knowledge of the thermal properties of garnets is therefore of great geophysical importance in the characterization of the thermal structure of the deep interior of the Earth. Considerable effort has been made to study the vibrational and thermodynamic properties of garnets by heat capacity, infra-red, Raman spectroscopic, and ultrasonic techniques and to understand these properties in terms of models for the lattice dynamics of these minerals. 2 However the same cannot be said about thermal expansion measurements. After the early compilation ∗ On leave from School of Physics, University of Hyderabad, Hyderabad 500 046, India. 1915 Int. J. Mod. Phys. B 2007.21:1915-1922. Downloaded from www.worldscientific.com by BILKENT UNIVERSITY on 09/29/17. For personal use only.