Anomalous Behavior of the ν₁Mode of PO₄Tetrahedrons in Rb_1-x(NH₄)_xH₂PO₄Mixed Crystals

Abstract

The ν 1 band of PO 4 tetrahedrons in Rb 1- x (NH 4 ) x H 2 PO 4 mixed crystals has been measured in the temperature region from 30 K to room temperature by Raman spectroscopy. An anomaly has been found in the temperature dependence of the ν 1 frequency of the mixed crystals. The glass-formation temperature ( T m ) has been estimated for the mixed crystals. This value of T m is higher than that estimated from the variation of the lattice constants. Raman scattering is useful to determine the onset temperature for the glass formation of those mixed crystals.