Temperature-dependent Raman scattering of KTa1-xNbxO3 thin films

TL;DR

This study investigates how temperature affects the Raman spectra of KTa1-xNbxO3 thin films, revealing phase transition behaviors similar to bulk materials but with shifted transition temperatures due to strain effects.

Contribution

It provides new insights into the temperature-dependent phase transitions of KTa1-xNbxO3 thin films and highlights the influence of biaxial strain on ferroelectric properties.

Findings

Phase sequence similar to bulk KNbO3

Transition temperatures are up to 50 K higher in films

Enhanced ferroelectricity due to biaxial strain

Abstract

We report a Raman scattering investigation of KTa1-xNbxO3 (x = 0.35, 0.5) thin films deposited on MgO and LaAlO3 as a function of temperature. The observed phase sequence in the range from 90 K to 720 K is similar to the structural phase transitions of the end-member material KNbO3. Although similar in the phase sequence, the actual temperatures observed for phase transition temperatures are significantly different from those observed in the literature for bulk samples. Namely, the tetragonal (ferroelectric) to cubic (paraelectric) phase transition is up to 50 K higher in the films when compared to bulk samples. This enhanced ferroelectricity is attributed to biaxial strain in the investigated thin films.