Raman spectroscopy of (K,Na)NbO3 and ((K,Na)1-xLix)NbO3

TL;DR

This study uses Raman spectroscopy to analyze phase transitions in (K,Na)NbO3 and Li-doped variants, revealing homogeneous ferroelectric phase transitions and a potential structural phase boundary at low Li concentrations.

Contribution

It provides detailed Raman spectral analysis across phases and identifies the impact of Li doping on phase boundaries in (K,Na)NbO3.

Findings

Homogeneous and hysteretic phase transitions in Li-free crystal

Distinct Raman patterns in low-temperature phase with Li doping

Possible structural phase boundary at Li concentration below 2%

Abstract

A Raman scattering spectroscopy study is reported through all four phases of a (K0.5Na0.5)NbO3 crystal and ((K0.5Na0.5)1-xLix)NbO3 for x=0.02 and 0.03. The transitions among the ferroelectric phases in the Li-free crystal are homogeneous and strongly hysteretic, with no evidence of a mixed-phase region between the rhombohedral and orthorhombic phases. The Raman pattern in the lowest-temperature phase in the Li-doped material differs significantly from that found for x=0 and suggest a structural phase boundary exists at for a Li concentration of less than 2%.