A combinatory ferroelectric compound bridging simple ABO3 and A-site-ordered quadruple perovskite

Jianfa Zhao,Lei Duan,Xudong Shen,Richeng Yu,Xiao Wang,Jun Gao ,Zhi Li,Yang Ren,Xiancheng Wang,Q Huang ,Qingqing Liu,Xi Shen,Chien Te Chen ,Lipeng Cao,Jinlong Zhu,L H Tjeng ,Yuting Qian,C Dong ,Shih Chang Weng ,Wenmin Li,Martha Greenblatt,Hong Ji Lin ,Hongming Weng,Chongwen Ren,Yao Long ,Zheng Deng,Zhiwei Hu,Runze Yu,Jun Zhang,Jin Chen

doi:10.1038/s41467-020-20833-6

Abstract

The simple ABO3 and A-site-ordered AA′3B4O12 perovskites represent two types of classical perovskite functional materials. There are well-known simple perovskites with ferroelectric properties, while there is still no report of ferroelectricity due to symmetry breaking transition in A-site-ordered quadruple perovskites. Here we report the high pressure synthesis of an A-site-ordered perovskite PbHg3Ti4O12, the only known quadruple perovskite that transforms from high-temperature centrosymmetric paraelectric phase to low-temperature non-centrosymmetric ferroelectric phase. The coordination chemistry of Hg2+ is changed from square planar as in typical A-site-ordered quadruple perovskite to a rare stereo type with 8 ligands in PbHg3Ti4O12. Thus PbHg3Ti4O12 appears to be a combinatory link from simple ABO3 perovskites to A-site-ordered AA′3Ti4O12 perovskites, sharing both displacive ferroelectricity with former and structure coordination with latter. This is the only example so far showing ferroelectricity due to symmetry breaking phase transition in AA′3B4O12-type A-site-ordered perovskites, and opens a direction to search for ferroelectric materials.

Highlights

The simple ABO3 and A-site-ordered AA′3B4O12 perovskites represent two types of classical perovskite functional materials
For the simple ABO3 perovskite, the 12-fold coordinated A-site is often occupied by large size ions such as alkali metal, alkaline earth or lanthanide cations and the 6-fold coordinated B-site is often occupied by transition metals (TMs) to satisfy the so called tolerance factor t =/√2(rB + rO) with t usually in the range of 0.75 to 1.05 for stable perovskite compounds[1,18]
The origins of ferroelectricity are discussed based on the comprehensive characterizations of crystal structure using both neutron and synchrotron x-ray diffractions and density functional theory (DFT) calculation

Summary

Introduction

The simple ABO3 and A-site-ordered AA′3B4O12 perovskites represent two types of classical perovskite functional materials. The small TM ion at the A′-site causes the distortion of BO6 octahedron in AA′3B4O12 perovskite, usually resulting in a cubic crystal structure with space group Im-325. An AA′3B4O12 type A-site-ordered perovskite oxide, PbHg3Ti4O12 ( PHTO) was designed and synthesized at high pressure and high temperature conditions.

Results

Conclusion