Features of phase transitions in nanosized powders KTa0.7Nb0.3O3

Abstract

Raman spectra of the nanopowder solid solution КТа0.7Nb0.3O3 were obtained and investigated for the first time. The compound was synthesized by a new technology. Temperature dependences of the in-tensity, width and frequency of the В1(TO2), А1(TO1), В1(TO3), А1(ТO3) and В2(TO3) modes are thoroughly analyzed. A significant narrowing of the temperature interval, including three phase transitions, is registered. The interval amounts 100°, from about –130 °С to –30 °С. In nanopowders KNbO3 the interval is almost 500°, from 0 °С to 475 °С. It was found that the temperatures of each of the phase transitions are shifted in different way, in particular: a low-temperature transition at 20° lower, the middle transition at 10° higher, and a ferroelectric phase transition occurs at 10° lower than the corres-ponding transitions in macrocrystals KТa0.7Nb0.3O3.