The bulk nanograined Bi2Te3 material with various mean grain size changing from similar to 51 to similar 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 (*) , for self-diffusion process responsible for grain growth at sintering of material under study. Analysis of the V (*) (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.