High-Tc Realization of Lead-Free Halide Hybrid Ferroelectrics via Steric Confinement Modulation

作者：Chen, Qin; Jiang, Haidong; Fan, Yipeng; Li, Zhou; Ye, Huang; Yao, Yunpeng; Chen, Shuang^*; Ji, Chengmin^*; Zhang, Shuhua^*; Luo, Junhua^*

来源：Advanced Functional Materials, 2023, 33(14).

DOI：10.1002/adfm.202213964

• ferroelectrics
• high-T-c
• hybrid perovskites
• lead-free
• steric confinements

Hybrid organic-inorganic perovskite (HOIP) ferroelectrics with high Curie temperature (T-c), typified by the lead halide hybrid perovskite ferroelectrics, are developing rapidly owing to their maneuverable ferroelectricity at high temperatures. However, acquiring high-T-c lead-free HOIP ferroelectrics via rational strategy still needs development. In this study, a brand-new program by modulating the steric confinement in a cuplike cavity to design high-T-c bismuth-halide ferroelectrics [H(2)mdap]BiX5 (H(2)mdap = N-Methyl-1,3-Propanediamine, X = Cl (1), Br (2), I(3)) is proposed. Emphatically, the T-c enhanced dramatically from 264 K of 3 to 318 K of 2 and 377 K of 1, induced by the substitution of Br and Cl to I, accompanied with an interesting transition from second-order phase transition (for 3) to the first-order one (for 1 and 2). The extent of T-c increase is up to 113 K, which far outweighs that of reported Pb-halide hybrid ferroelectrics. Structural and computational analyses elucidate that this unprecedented improvement of T-c is due to the higher phase transition energy barriers induced by modulating the steric confinement of cuplike cavity via halogen substitution. These results will provide new inspiration for designing high-T-c lead-free HOIP ferroelectrics.

• 单位
  中国科学院研究生院; 南京大学; 中国科学院福建物质结构研究所; 桂林理工大学