Negative thermal expansion property in Nb14W3O44

Nb14W3O44, a promising electrode material of lithium-ion batteries/capacitors, was prepared using a solid-state method. Its geometrical structure, phase diagram, and thermal expansion properties were all thoroughly investigated. The material has a tetragonal structure and an intriguing linear negative thermal expansion (NTE) property with an impressive coefficient of thermal expansion (−4.27 × 10−6 K−1, 300–433 K). The NTE phenomenon can be attributed to the vibrations of the bridge-site atoms, which caused the coupling rotation of the rigid unit models. The lattice distortion, and pores could also affect the thermal expansion performance in the bulk materials.