Realizing negative thermal expansion over an extended temperature range in PbTiO₃-based perovskites

Negative thermal expansion (NTE) is fascinating, as it involves a material’s volume contraction rather than expansion upon heating. Although NTE lattices typically have highly flexible frameworks, the magnitude of NTE is often very small, and they frequently exhibit a narrow temperature range for controllable NTEs. It remains a great challenge to achieve large NTE while maintaining a wide temperature operation range from the currently available materials. Herein, we present a novel PbTiO₃ (PT)-based perovskite system, (1−x)PbTiO₃–xBiYbO₃, synthesized via a distinctive high-pressure and high-temperature technique. Compared with pristine PbTiO₃ (c/a = 1.064), the system exhibited unusual enhanced tetragonalities. Consequently, NTE over an extended temperature range has been realized in 0.95PbTiO₃–0.05BiYbO₃ ( ${\overline{\alpha }}_V$ = −2.18×10⁻⁵ K⁻¹, 300–820 K) and 0.90PbTiO₃−0.10BiYbO₃ ( ${\overline{\alpha }}_V$ = −1.85×10⁻⁵ K⁻¹, 300–850 K) compared with that of pristine PbTiO₃ ( ${\overline{\alpha }}_V$ = −1.99×10⁻⁵ K⁻¹, 300–763 K). Our experimental and theoretical studies indicate that the improved tetragonality and expanded NTE temperature range result from larger ionic displacements and an enhanced asymmetric charge distribution, both of which are induced by BiYbO₃ substitution. The present study presents a new example of an NTE across a broad temperature range, highlighting its potential as an effective thermal expansion compensator.