title: Large negative thermal expansion in non-perovskite lead-free ferroelectric Sn2P2S6.
abstract: Functional materials showing both negative thermal expansion (NTE) and physical performance, such as ferroelectricity and magnetism, have been extensively explored in the past decade. However, among ferroelectrics a remarkable NTE was only found in perovskite-type PbTiO3-based compounds. In this work, a large NTE of -4.7 × 10(-5) K(-1) is obtained in the non-perovskite lead-free ferroelectric Sn2P2S6 from 243 K to TC (338 K). Structure refinements and first-principle calculations reveal the effects of the Sn(ii) 5s-S 3p interaction on spontaneous polarization and its correlation with NTE. Then the mechanism of spontaneous volume ferroelectrostriction (SVFS) is verified and it could well elucidate the nature of NTE in ferroelectric Sn2P2S6. This is the first case to demonstrate the unusual NTE behavior by SVFS in a non-perovskite lead-free ferroelectric material.
authors: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China. xing@ustb.edu.cn.
authors: Yangchun
authors: Y
authors: Rong
authors: Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China.
authors: Menglei
authors: M
authors: Li
authors: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China. xing@ustb.edu.cn.
authors: Jun
authors: J
authors: Chen
authors: Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China.
authors: Mei
authors: M
authors: Zhou
authors: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China. xing@ustb.edu.cn.
authors: Kun
authors: K
authors: Lin
authors: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China. xing@ustb.edu.cn.
authors: Lei
authors: L
authors: Hu
authors: Department of Chemistry and Chemical Engineering, University of Science and Technology Beijing, Beijing 100083, China.
authors: Wenxia
authors: W
authors: Yuan
authors: Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China.
authors: Wenhui
authors: W
authors: Duan
authors: Department of Chemistry and Chemical Engineering, University of Science and Technology Beijing, Beijing 100083, China.
authors: Jinxia
authors: J
authors: Deng
authors: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China. xing@ustb.edu.cn.
authors: Xianran
authors: X
authors: Xing