Pressure effect on the Raman spectra of RbAIF₄ and KAIF₄: A pressure induced martensitic phase transition in KAIF₄

Abstract

The Raman spectra of RbAIF₄ (phase II) and KAIF₄ (Phase II and IV) at room temperature were measured under hydrostatic pressure up to 10 GPa and 4 GPa, respectively. While the frequencies of the former do not exhibit any significant singularity against temperature, in the case of KAIF₄ a strong frequency jump is observed at 0.21 GPa. This is attributed to the martensitic phase transition already observed as a function of temperature. The pressure dependence of the frequencies in the two compounds is discussed in relation to their structure and the structural phase transitions.

Key Words:

• High pressure
• phase transition
• Raman spectrum