Phase Transition and Exceptional Negative Thermal Expansion in Pb3-xSrx(VO4)2: the Role of Sr Substitution

Negative thermal expansion (NTE) materials continue to attract significant interest due to their unique properties and potential applications. Despite progress in NTE research, achieving precise control over the coefficient of thermal expansion (CTE) remains challenging. Recently, we found that Pb3-xSrx(VO4)2 (x=0-0.5) undergoes a phase transition accompanied by a significant volume contraction of more than 1% (Figure 1). Notably, as the Sr content increases, the transition temperature shifts to lower values. Interestingly, Pb2.5Sr0.5(VO4)2 exhibits an exceptionally negative CTE of -19.7×10-5 K-1 in the 15–35 °C range, the lowest reported for materials under ambient conditions. However, the mechanisms underlying this phase transition and the role of Sr remain unclear. In this context, EXAFS can provide valuable insights into the structural and dynamic factors driving these behaviors, helping the design of materials with tailored thermal expansion.