Grain structure evolution at sintering of the bulk Bi sub(2)Te sub(3) nanomaterial under hot pseudo-isostatic pressure

The bulk nanograined Bi sub(2)Te sub(3) material with various mean grain size changing from ~51 to ~97 nm was prepared by microwave-assisted solvothermal method and hot pseudo-isostatic pressure. The mean grain size values obtained for various pressures, P, and temperatures, T, of the sintering process were used to estimate the changes of activation volume, V super( * ), for self-diffusion process responsible for grain growth at sintering of material under study. Analysis of the V super( * )(P) dependences taken at 573 and 673 K allowed us to suggest that one interstitial diffusion mechanism takes place at 573 K, while the diffusion mechanism is assumed to be changed from the vacancy mechanism at low pressures (2 and 4 GPa) to the interstitial mechanism at high pressures (6 and 8 GPa) at 673 K.