Negative thermal expansion property of CuMoO4

The triclinic copper (II) molybdate (α-CuMoO4) was synthesized by a solid state method and its negative thermal expansion (NTE) was systematically studied. The results show that α-CuMoO4 exhibits non-linearly NTE and the coefficient of thermal expansion (CTE) is −4.40 × 10−6/K, when the temperature ranges from room temperature (RT) to 390 K. Its negative expansion behavior may be caused by the charge transferred from O2− to Cu2+, resulting that a part of the CuO6 octahedron transferred to CuO5 hexahedron, and the CuO bond length in CuO5 hexahedron became shorter than in CuO6 octahedron. The synthetic action of d9Jahn-Teller effect of Cu2+ and small amount of pores may also contribute to the NTE of CuMoO4. CuMoO4 also has excellent photocatalytic properties, luminescent properties, dielectric properties and thermal cycling properties. The NTE and other excellent properties of CuMoO4 make the material have great prospects in application.