Negative and zero thermal expansion in α-(Cu2−xZnx)V2O7 solid solutions†
Negative or zero thermal expansion (NTE or ZTE) of materials is intriguing for controllable thermal expansion. We report a series of orthorhombic α-Cu2−xZnxV2O7 (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-Cu1.8Zn0.2V2O7. This work presents an effective method to realize ZTE in anisotropic framework systems.