Negative and zero thermal expansion in α-(Cu2−xZnx)V2O7 solid solutions

Abstract

Negative or zero thermal expansion (NTE or ZTE) of materials is intriguing for controllable thermal expansion. We report a series of orthorhombic α-Cu_2−xZn_xV₂O₇ (x = 0, 0.1, 0.2), in which the volumetric coefficients of thermal expansion are successfully tuned from −10.19 × 10⁻⁶ K⁻¹ to −1.58 × 10⁻⁶ K⁻¹ in the temperature range of 100–475 K by increasing the content of Zn²⁺. It has been revealed that the transverse vibrations of oxygen bonded with vanadium are dominant in the contraction of the bc plane, leading to the overall volume NTE in α-Cu₂V₂O₇. The introduction of Zn²⁺ densifies the crystal structure, which is presumed to suppress the space of transverse vibrations and results in the ZTE in α-Cu_1.8Zn_0.2V₂O₇. This work presents an effective method to realize ZTE in anisotropic framework systems.