Enhanced Negative Thermal Expansion Property Deduced by the Breaks of Superstructure

The HfV2O7/HfMo2O8 composite were prepared in situ. The phase, structure and thermal expansion property were analyzed. The results indicate the composite consist of cubic HfV2O7 and hexagonal HfMo2O8. The two types of structures were coexisted and mixed uniformly, and interacted with each other. The mutual nested structure suppressed the formation of 3×3×3 superstructure in HfV2O7 (RT) introduced by the reaction in situ. The promoted coupled rotation of quasi-rigid polyhedron units could enhance the negative thermal expansion (NTE) property. The HfV2O7/HfMo2O8 composite exhibits excellent NTE property from 250 to 673 K (at least) with CTE -3.09 × 10-6 K-1. The good NTE property and thermal stability over a wide temperature range, especially near the RT range, bring a good potential application in designing zero thermal expansion materials.