A Chemical-Pressure-Induced Phase Transition Controlled by Lone Electron Pair Activity.

The chemical pressure approach offers a new paradigm for property control in functional materials. In this work, we disclose a correlation between the β → α pressure-induced phase transition in SnMoO ₄ and the substitution process of Mo ⁶⁺ by W ⁶⁺ in SnMo _{1- x} W _x O ₄ solid solutions ( x = 0-1). Special attention is paid to discriminating the role of the lone pair Sn ²⁺ cation from the structural distortive effect along the Mo/W substitution process, which is crucial to disentangle the driven force of the transition phase. Furthermore, the reverse α → β transition observed at high temperature in SnWO ₄ is rationalized on the same basis as a negative pressure effect associated with a decreasing of W ⁶⁺ percentage in the solid solution. This work opens a versatile chemical approach in which the types of interactions along the formation of solid solutions are clearly differentiated and can also be used to tune their properties, providing opportunities for the development of new materials.