Enhanced negative thermal expansion and optical absorption of In0.6(HfMg)0.7Mo3O12 with oxygen vacancies

A negative thermal expansion (NTE) material In0.6(HfMg)0.7Mo3O12 with oxygen vacancies was successfully synthesized through He atmosphere annealing. It was found that the introduction of oxygen vacancies enhanced the coefficient of NTE by about an order of magnitude larger. It can be attributed to the increased flexibility of the polyhedra in the framework structure. The introduction of oxygen vacancies also weakened the MO bonds and obviously enhanced the optical absorption in the visible light region. This work provides a promising strategy to effectively improve the NTE and optical properties of traditional NTE materials by introducing oxygen vacancies.