Effects of anisotropy and annealing on microhardness of In x Bi2?x Te3 (x=0·1 to 0·5) single crystals

The crystals of In _x Bi_2−x Te₃ (x=0·1 to 0·5) have been grown by zone-melting method. In order to study anisotropy exhibited by the (0001) plane of the crystals, the directional hardness was determined by producing indentations at various azimuthal orientations of the indentor with respect to the surface over a range 0–180°. The crystal was rotated about the indentor axis in steps of 15° while keeping applied load and loading time constant at 50 g and 20 sec, respectively. For annealing study, the sample was kept at a temperature of 375°C. It was observed that softening of crystal takes place and the hardness decreases to a considerable extent.