High temperature structure and vibrational properties of GdVO4

In this manuscript the temperature evolution of crystal structure and vibrational properties of tetragonal GdVO4 as observed from in situ high temperature powder XRD and Raman spectroscopic studies are reported. The material shows anisotropic expansion with a larger coefficient of thermal expansion along c-axis (alpha c) compared to that along the a-axis (alpha a). The average axial thermal expansion coefficients in the temperature range of 298-1373 K are: alpha a = 3.75 x 10-6 K-1 and alpha c = 11.1 x 10-6 K-1. The degree of anisotropy in thermal expansion decreases with increasing temperature. The thermal expansion behavior of GdVO4 was mainly contributed by the orientation and expansion of Gd-O bonds in the structure. The temperature dependent Raman spectroscopic investigations indicate decreasing trend of all the observed phonon mode frequencies. All the low energy modes show larger anharmonicity compared to the high energy stretching modes and they contribute significantly to the expansion of GdVO4.