João Nuno Gonçalves

Bismuth-based oxides with chemical formula ABiO3, where A = Ca, Zn, Mg, have been recently synthesized and suggested to host ferroelectricity. As these materials possess favorable optical properties, the presence of ferroelectricity with large polarization would further enhance the possible applications, for example, in photovoltaics by improving the separation of charge carriers. In this work, first-principles Density Functional Theory (DFT) calculations are performed to study the relative stability of the different polymorphs and to investigate the structural, electronic, and ferroelectric properties. Furthermore, the effect of compressive and tensile in-plane strain on the polarization and electronic properties is also considered. Our study suggests that CaBiO3 should have a large electric polarization (1.8 C/m2) comparable to the one of BiFeO3. Interestingly, the very high polarization appears with only slightly anomalous values of Born effective charges, which would point out a dominant ionic contribution. Our results call for further studies, both from experimental and theoretical sides, to confirm the large electric polarization CaBiO3 predicted in this work. For ZnBiO3 and MgBiO3, we have demonstrated that, up to large values of strain, the perovskite structure retains favorable ferroelectric and electronic (band gap) properties.