High-temperature Raman study of K2ZrF6 phase transitions

Abstract Series of K 2 ZrF 6 Raman spectra measured at various temperatures as part of specified time/temperature regimes have been analyzed by the Principal Component Analysis (PCA) and Multivariate Curve Resolution (MCR) methods. The obtained MCR scores indicated the relative abundance of individual K 2 ZrF 6 phases, and the temperatures of the phase transitions could be obtained from them. Eight linear time/temperature regimes were used, with heating/cooling rates of 1 °C/min or 5 °C/min. Two target temperatures were used. Heating to a maximum temperature of 255 °C resulted in the formation of a β phase, which persisted on cooling to room temperature. However, heating to 310 °C resulted in formation first of the β , and then of the γ phase; on cooling to RT, the γ to α transition was seen. These results confirmed the irreversible character of the α to β and γ to α transitions. The transient emergence of β phase during the γ to α transition was observed.