Enhanced Negative Thermal Expansion Property Deduced by the Breaks of Superstructure

The HfV 2 O 7 /HfMo 2 O 8 composite were prepared in situ . The phase, structure and thermal expansion property were analyzed. The results indicate the composite consist of cubic HfV 2 O 7 and hexagonal HfMo 2 O 8 . 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 HfV 2 O 7 (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 HfV 2 O 7 /HfMo 2 O 8 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.