Size effects in the temperatures of phase transitions in KNbO3 nanopowder

Abstract

The paper reports on thorough Raman-scattering study of newly synthesized nanoscale powders of potassium niobate (KNbO3) aimed at evaluating the possible modification of the phase transition temperatures versus the corresponding bulk values. We register a significant expansion of the temperature ranges of all phase transitions, which is attributed to a wide distribution of particle sizes. An average temperature of each phase transition shifts to the high-temperature region differently, namely by 10°, 25°, and 40°, as compared with corresponding transition temperature in bulk crystals of KNbO3 and amounts 0, 248, and 475 °C, respectively. In the range from 100 to 110 °C, we also find the features, which could be associated with an additional rearrangement of the structure.