Enhanced tetragonality and large negative thermal expansion in a new Pb/Bi-based perovskite ferroelectric of (1 -X) PbTiO₃- xBi (Zn_1/2V_1/2)O₃

The exploration of a large negative thermal expansion (NTE) over a wide temperature range has been an important subject in materials science, since the overall coefficient of thermal expansion (CTE) of ordinary materials can be effectively tailored by the introduction of NTE materials. Here, we successfully achieved a large NTE within a broad temperature range in a new Pb/Bi-based ferroelectric of (1 - x)PbTiO₃-xBi(Zn_1/2V_1/2)O₃ by means of improving the ferroelectricity of PbTiO₃. The present system exhibits an unusual enhanced tetragonality, large spontaneous polarization (P_S), and high Curie temperature (T_C). Specifically, the x = 0.1 compound exhibits an enhanced CTE of -2.10 × 10^-5 °C^-1 from room temperature (RT) up to its T_C of 600 °C, which is in contrast to that of pristine PbTiO₃ (-1.99 × 10^-5 °C^-1, RT-490 °C). More intriguingly, a large volume shrinkage (ΔV ≈ -1%) has also been observed during the ferroelectric-to-paraelectric phase transition. According to experimental and theoretical studies, the large NTE is attributed to the enhanced P_S derived from the strong hybridization of Pb/Bi-O and Ti/Zn/V-O through the substitution of the polar Bi(Zn_1/2V_1/2)O₃ perovskite. The present study demonstrates that a large NTE within a wide temperature range can be achieved in PbTiO₃-based ferroelectrics by improving its ferroelectricity through introducing isostructural polar perovskites.