Study of a polymorphic phase transition in KNNLiTaLa0.01 by Raman spectroscopy

Using Raman spectroscopy, the study of a polymorphic phase transition in the KNNLiTaLa0.01 compound is presented. An analysis of the behavior with temperature, wavenumber and half width at full maximum of the individual bands, corresponding to the vibration modes of the (Nb/Ta)O6 octahedra of the KNNLiTaLa0.01 compound’s structure, is performed. This analysis determined that the polymorphic phase transition of the KNNLiTaLa0.01 compound occurs in the 90 to 105°C temperature interval. Using the Hard Mode Spectroscopy method, the value of the critical exponent of the order parameter was determined to be β ≈ ½, indicative of a second order transition.