A Combinatory Ferroelectric Compound Bridging Simple ABO3 and A-site-Ordered Qudruple Perovskite

Abstract

The simple ABO3 and A-site-ordered AA′3B4O12 perovskites represent two types of the most classical perovskite-based functional materials. While there are well-known simple perovskites with ferroelectric properties, so far there is no report of ferrolectricity due to symmetry breaking transition in A-site-ordered quadruple perovskites, AA′3B4O12. Here we report the synthesis at high pressure and temperature of a new A-site-ordered perovskite, PbHg3Ti4O12. Remarkably, PbHg3Ti4O12 is the only known quadruple perovskite that transforms from a high-temperature centrosymmetric (Im-3), paraelectric phase to a low-temperature, non-centrosymmetric (Imm2) ferroelectric phase. Moreover, the average ionic radius of A-site cations for PbHg3Ti4O12 is large~ 1.1 Å and the tolerance factor t is about 0.88. Surprisingly the coordination chemistry of Hg2+ is changed from the usual square planar as in typical A-site-ordered quadruple perovskite to a rare stereo type with 8 ligands in PbHg3Ti4O12 driven via pressures. Thus PbHg3Ti4O12 appears to be a combinatory link from simple ATiO3 perovskite to AA′3B4O12 type A-site-ordered perovskites, sharing both displacive ferroelectricity with the former and the structure coordination with the latter. This is the first example of ferroelectricity due to a symmetry breaking phase transition in AA′3B4O12-type A-site-ordered perovskite, and opens a new direction to search for ferroelectric materials in combinatory perovskites.

Design of High-Performance Lead-Free Quaternary Antiperovskites for Photovoltaics via Ion Type Inversion and Anion Ordering

“…54,78 An A-site-cation-ordered quadruple perovskite AA′ 3 B 4 O 12 (A = Pb 2+ ; A′ = Hg 2+ ; B = Ti 4+ ) and a B-site-cation-ordered Bi 3+ 2 Fe 3+ Al 3+ O 6 double perovskite have been synthesized. 79,80 Furthermore, a B-site-ordered double antiperovskite Li 6 O 2− S 2− I 2 has also been successfully synthesized. These experimental results suggest that the ordering of two isovalent ions on either A or B site is possible.…”