位移铁型电材料PbHg3Ti4O12：架起简单和多阶钙钛矿材料的桥梁

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

Zhao, J. F., Gao, J. C., Li, W. M., Qian, Y. T., Shen, X. D., Wang, X., Shen, X., Hu, Z. W., Dong, C., Huang, Q. Z., Cao, L. P., Li, Z., Zhang, J., Ren, C. W., Duan, L., Liu, Q. Q., Yu, R. C., Ren, Y., Weng, S.-C., Lin, H.-J., Chen, C.-T., Tjeng, L.-H., Long, Y. W., Deng, Z., Zhu, J. L., Wang, X. C., Weng, H. M., Yu, R. Z., Greenblatt, M. & Jin, C. Q.

Nat. Commun. 12, 747 (2021)
Research Highlight: 中科院（CAS）； 中科院物理所（IOP）

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 Asite- 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-siteordered perovskites, and opens a direction to search for ferroelectric materials.