Comparative study of phase transitions in polycrystalline and epitaxial BaTiO3 thin films by means of specific heat measurements

TL;DR

This study compares the thermal phase transition behaviors of polycrystalline and epitaxial BaTiO3 thin films using specific heat measurements, revealing similarities and differences in their phase transition characteristics.

Contribution

It introduces a modified 3w method for specific heat measurements and applies it to analyze phase transitions in different BaTiO3 thin film structures.

Findings

Polycrystalline films show similar specific heat and entropy evolution as nanograined ceramics.

Epitaxial films exhibit a diffused anomaly near 400 K with transition temperature shifting.

Thinnest films (50 nm) show no anomalies up to 480 K.

Abstract

The experimental data on the thermal properties of the nanostructured perovskite ferroelectrics are presented and analysed. The ability of the modified 3w method for specific heat measurements is discussed and illustrated by the thermal properties of the thin polycrystalline (BaTiO3 on fused SiO2, 50-1100 nm) and epitaxial (BaTiO3 on MgO, 50-500 nm) films. The similarity of specific heat, phase transition excess entropy evolution in polycrystalline films and nanograined ceramics is revealed. The data on the specific heat of epitaxial films show the extremely diffused anomaly near 400 K, the phase transition has the weak tendency of shifting to higher temperatures with the decreasing of the film thickness. No anomalies were detected for the thinnest (50 nm) film up to 480 K.