Realization of Negative Thermal Expansion in Lead-Free Bi0.5K0.5VO3 by the Suppression of Tetragonality

Zhao Pan; Takehiro Koike; Takumi Nishikubo; Lei Hu; Qiumin Liu; Yuki Sakai; Shogo Kawaguchi; Masaki Azuma

doi:10.1021/acs.inorgchem.1c03960

Realization of Negative Thermal Expansion in Lead-Free Bi_0.5K_0.5VO₃ by the Suppression of Tetragonality

Inorg Chem. 2022 Feb 28;61(8):3730-3735. doi: 10.1021/acs.inorgchem.1c03960. Epub 2022 Feb 11.

Authors

Zhao Pan¹, Takehiro Koike¹, Takumi Nishikubo^{1

2}, Lei Hu¹, Qiumin Liu¹, Yuki Sakai^{1

2}, Shogo Kawaguchi³, Masaki Azuma^{1

2}

Affiliations

¹ Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, Kanagawa 226-8503, Japan.
² Kanagawa Institute of Industrial Science and Technology, 705-1 Shimoimaizumi, Ebina, Kanagawa 243-0435, Japan.
³ Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI), Spring-8, 1-1-1 Kouto, Sayo-gun, Hyo̅go 679-5198, Japan.

PMID: 35148105
DOI: 10.1021/acs.inorgchem.1c03960

Abstract

Bi_1/2K_1/2VO₃ is a lead-free PbTiO₃-type compound with a tetragonality (c/a = 1.054) comparable to that of typical ferroelectric PbTiO₃ (c/a = 1.064) with negative thermal expansion (NTE) during the tetragonal-to-cubic phase transition; therefore, Bi_1/2K_1/2VO₃ is a potential lead-free NTE material if its metastable perovskite structure can be maintained at high temperatures. In the present experiment, electron doping in Bi_1/2K_1/2VO₃ was conducted through substituting K⁺ with La³⁺ to suppress the tetragonality and achieve NTE. La substitution successfully suppressed the tetragonality of Bi_1/2K_1/2VO₃ and also improved its thermal stability. Moreover, both composition- and temperature-induced tetragonal-to-cubic phase transitions occurred. In particular, a large volume shrinkage with a large negative thermal coefficient of expansion (CTE) was obtained for Bi_0.5K_0.46La_0.04VO₃ during the tetragonal-to-cubic phase transition (ΔV = -0.66%). Hence, this study extends the NTE family and also sheds light on the exploration of lead-free piezoelectric materials with controllable thermal expansion.