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 SnMoO₄ and the substitution process of Mo⁶⁺ by W⁶⁺ in SnMo_1-WO₄ solid solutions (x = 0-1). Special attention is paid to discriminating the role of the lone pair Sn²⁺ 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 SnWO₄ is rationalized on the same basis as a negative pressure effect associated with a decreasing of W⁶⁺ 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.