Pyroelectricity in Ferroelectric PbTiO3 Enhanced by A-Site Cation Contribution and Negative Thermal Expansion

The primary and secondary pyroelectric effect in ferroelectric tetragonal PbTiO3 perovskite oxide has been studied with quantum chemical methods. Hybrid PBEsol0 density functional method accurately reproduces the experimental crystal structure of PbTiO3 and enables systematic studies on the pyroelectricity, lattice thermal conductivity, and other physical properties of PbTiO3. Phonon anharmonicity and finite-temperature phonon properties necessary for the study of primary pyroelectricity are determined with the use of Self-Consistent Phonon Theory. Secondary pyroelectricity and the negative thermal expansion of PbTiO3 are investigated with quasi-harmonic approximation. In comparison to another tetragonal ferroelectric perovskite oxide BaTiO3, the primary pyroelectric coefficient of PbTiO3 is increased by the contributions of the polarized Pb(II) A-site cations, and the secondary pyroelectric coefficient is increased by the negative thermal expansion.