Large Negative Thermal Expansion Induced by Synergistic Effects of Ferroelectrostriction and Spin Crossover in PbTiO₃-Based Perovskites

Abstract

The discovery of unusual negative thermal expansion (NTE) provides the opportunity to control the common but much desired property of thermal expansion, which is valuable not only in scientific interests but also in practical applications. However, most of the available NTE materials are limited to a narrow temperature range, and the NTE effect is generally weakened by means of various modifications. Here, we report an enhanced NTE effect that occurs over a wide temperature range ( V  = -5.24 × 10 -5 °C -1 , 25-575 C), and this NTE effect is accompanied by an abnormal enhanced tetragonality, a large spontaneous polarization, and a G-type antiferromagnetic ordering in the present perovskite-type ferroelectric of (1-x)PbTiO3-xBiCoO3. Specifically, for the composition of 0.5PbTiO3-0.5BiCoO3, an extensive volumetric contraction of ~4.8 % has been observed near the Curie temperature of 700 °C, which represents the highest level in PbTiO3-based ferroelectrics.According to our experimental and theoretical results, the giant NTE originates from a synergistic effect of the ferroelectrostriction and spin-crossover of cobalt on the crystal lattice. The actual NTE mechanism is contrasted with previous functional NTE materials, in which the NTE is simply coupled with one ordering such as electronic, magnetic, or ferroelectric ordering. The present study sheds light on the understanding of NTE mechanisms and it attests that NTE could be simultaneously coupled with different orderings, which will pave a new way toward the design of large NTE materials.

Extraordinary anisotropic thermal expansion in photosalient crystals

“…Molecular solids in general are expected to have moderate positive thermal expansion (PTE) due to increasing anharmonic vibrational amplitudes of their molecules. In many cases, structural peculiarities may give rise to very large PTE (Goodwin et al, 2008;Das et al, 2010Das et al, , 2015Engel et al, 2014;Alimi et al, 2018;Janiak et al, 2018;Zhou et al, 2015;Yang et al, 2009) or even NTE (Chapman et al, 2006;Goodwin et al, 2005;Margadonna et al, 2004;Pan et al, 2019;Phillips et al, 2008;Wu et al, 2008) upon heating (Table S3). It is interesting to note that the parallel alignment of the one-dimensional assemblies in 1-3 promotes large thermal expansion from room temperature to 200 C in addition to photoreactivity and the PS effect.…”

Understanding the effect of water transport on the thermal expansion properties of the perovskites BaFe0.6Co0.3Nb0.1O3−δ and BaCo0.7Yb0.2Bi0.1O3−δ

“…For solid materials, many physical or physicochemical processes can cause the phenomenon of negative thermal expansion (NTE) with an increase in temperature. The most frequently reported ones are phase transitions (ice/water), electronic valence transitions [19][20][21], ferroelectric ordering [22][23][24], contraction of zeolites (siliceous or ZrW 2 O 8 ) by changing in bridging M-O-M bond angles [25][26][27] or orbital and magnetic ordering [28]. While there have been some reports of perovskite materials with NTE during the last three decades [29][30][31][32][33], such observations are unusual as perovskites in the form ABO 3 generally do not exhibit NTE properties [30].…”

Tuning Crystal Field Potential by Orbital Dilution in Strongly Correlated d4 Oxides

“…It is interesting to point out that similar competing effects between electron correlations and lattice distortions do not occur in transition metal oxides with e g orbital degrees of freedom, whereas the Jahn-Teller distortions are typically cooperating with the orbital exchange of electronic origin [6,44,47,48]. The local lattice distortions associated with the variation of the orbital order at the metal-insulator transition have been detected by EXAFS and XANES in manganites [49] and recently in PbTiO 3 -based perovskites systems [50]. Therefore, we expect that further experiments will provide interesting information in this field.…”