Negative Thermal Expansion in a Large Molybdate and Tungstate Family

Negative thermal expansion has been discovered in a very large family of oxides represented by the formulaA2M3O12, where theAandMcations are coordinated by oxygen octahedrally and tetrahedrally, respectively. In the case of Sc2W3O12, negative thermal expansion occurs over a temperature range of at least 10 to 1200 K. Ceramic bars of Sc2W3O12show a contraction with increasing temperature greater than that reported for any other material. Trends observed in this largeA2M3O12family have provided insights on why many compounds showing negative thermal expansion cease to show this behavior below a certain temperature. Some members of this family show positive thermal expansion. Solid solutions have been made which show very low thermal expansion.