A Phenomenological Thermodynamic Potential for CaTiO3 Single Crystal

TL;DR

This paper develops a thermodynamic model for CaTiO3 that captures the coupling between antiferrodistortive and ferroelectric transitions, explaining how stress and strain influence phase behavior in thin films.

Contribution

It introduces a comprehensive thermodynamic potential describing AFD and ferroelectric coupling in CaTiO3, aligning well with experimental data.

Findings

Transition temperatures depend on stress and strain conditions.

Ferroelectric transition is suppressed by AFD transition.

Constructed a phase diagram for CaTiO3 thin films.

Abstract

The antiferrodistortive (AFD) structural transitions of calcium titanate (CaTiO3) at ambient pressure have been extensively studied during the last few years. It is found none of the AFD polymorphs is polar or ferroelectric. However, it was recently shown theoretically and later experimentally confirmed that a ferroelectric transition in CaTiO3 can be induced by tensile strains. The ferroelectric instability is believed to be strongly coupled to the AFD soft modes. In this article, we present a complete thermodynamic potential for describing the coupling between the AFD and ferroelectric phase transitions. We analyzed the dependence of transition temperatures on stress and strain condition. Based on this potential, a (001) CaTiO3 thin film diagram was constructed. The results show good agreement with available experimental observations. The strong suppression of ferroelectric transition by the AFD transition is discussed.