Thermal expansion of ZnCr2Se4 was investigated from room temperature to 301 degrees C. Zinc chromium selenide, an antiferromagnetic spinel with a helical spin structure and of space group Fd 3m (Oh7), showed unusual behaviour above 340 degrees C on DTA. Thermal expansion of this compound in the temperature range 26-301 degrees C is reported in this paper. The average value of its thermal expansion coefficient in the specified temperature range is found to be 11.69*10-6 degrees C-1.

The lattice parameters of the compound cadmium stanni-diphosphide (CdSnP2) have been determined at different temperatures in the range 28 to 536 degrees C. From these data, the thermal expansion and the tetragonal distortion have been evaluated at various temperatures. The linear thermal expansion coefficients along the a and c axes are estimated to be alpha a=6.55*10-6 K-1 and alpha c=2.75*10-6 K-1 respectively and the axial ratio c/a, changes with a coefficient of -3.63*10-6 K-1. This study indicates the anisotropy between the axial expansion coefficients ( alpha a> alpha c) and an increase in the tetragonal distortion, 2-(c/a), with temperature. These results have been interpreted in terms of the thermal expansion of the Cd-P and Sn-P bonds of the CdSnP2 lattice.

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