First-principles study of the composition, cation arrangement, and local structure in high-performance Bi(Me3+)O3–PbTiO3 (Me3+ = Ga, Sc, In) ferroelectric solid solutions

Abstract

Ferroelectric perovskite solid solutions are of interest due to their extensive use in modern electronic devices. Cation off-centering is the dominant mechanism of ferroelectricity in perovskite oxides, and it was shown that the average off-centering of these cations can be used to predict some of the essential properties of solid solutions. In this work, we use first-principles density functional theory to investigate the dependence of the cation displacements on the ionic size, amount of substitution, O6 tilt, and locations of the Bi and Me3+ cations in xBiMe3+O3–(1 − x)PbTiO3 (Me3+ = Ga, Sc, In) solid solutions. We carry out our calculations for the x = 0.125 and x = 0.25 BiMe3+O3 substitution concentrations and the ⟨100⟩, ⟨110⟩, ⟨111⟩, ⟨011⟩, and ⟨001⟩ arrangements of the BiMe3+O3 substituent units. We demonstrate that the substitution of larger ions leads to greater variation in the energy and cation displacement magnitudes of the different cation arrangements. Our study reveals that cation displacements are governed by the interplay of the volume expansion effect that favors higher displacements and the cooperative O6 tilt effect that decreases the displacements. Both of these effects increase with greater ionic radius and their relative strengths depend on the cation arrangement. We also illustrate how negative pressure can be achieved experimentally by the doping of large In cations in these solid solutions. Understanding the dependence of the different directional arrangements, O6 tilting, and the effect of ionic size is important for precise prediction of ferroelectric materials properties and enables rational design of new piezoelectric materials.