The rare physical property of negative thermal expansion (NTE) is intriguing because materials with a large NTE over a wide temperature range can serve as high-performance thermal expansion compensators. However, the applications of NTE are hindered by the fact that most of the available NTE materials show small magnitudes of NTE, and/or NTE occurs only in a narrow temperature range. Herein, for the first time, we investigated the effect of anion substitution instead of general Pb/Ti-site substitutions on the thermal expansion properties of a typical ferroelectric NTE material, PbTiO3. Intriguingly, the substitution of S for O in PbTiO3 further increases the tetragonality of PbTiO3. Consequently, an unusually enhanced NTE with an average volumetric coefficient of thermal expansion of [small alpha, Greek, macron]V = −2.50 × 10−5 K−1 was achieved over a wide temperature range (300–790 K), which is in contrast to that of pristine PbTiO3 ([small alpha, Greek, macron]V = −1.99 × 10−5 K−1, RT–763 K). The intensified NTE is attributed to the enhanced hybridization between Pb/Ti and O/S atoms by the substitution of S, as evidenced by our theoretical investigations. We therefore demonstrate a new technique for introducing mixed anions to achieve a large NTE over a wide temperature range in PbTiO3-based ferroelectrics.

This work was supported by the National Key R&D Program of China (Grant No. 2021YFA1400300), the National Natural Science Foundation of China (22271309, 12304268, 11934017, 11921004, and 12261131499), the Grants-in-Aid for Scientific Research (JP18H05208 and JP19H05625) from the Japan Society for the Promotion of Science (JSPS), the Beijing Natural Science Foundation (Grant No. Z200007), the Chinese Academy of Sciences (Grant No. XDB33000000), and the Kanagawa Institute of Industrial Science and Technology. The synchrotron X-ray powder diffraction experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (2023B1575 and 2024A1506). XANES at the S-K edge was performed at beamline 4B7A of Beijing Synchrotron Radiation Facility (BSRF). Technical and human support provided by the DIPC Supercomputing Center is gratefully acknowledged.

Zhao Pan, et al.

Peer reviewed