Phase transition and near-zero thermal expansion of Zr0.5Hf0.5VPO7.

The Zr0.5Hf0.5VPO7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction (XRD), Raman spectroscopy, thermal dilatometry, and scanning electron microscopy (SEM) are used to investigate the structure, the phase transition, and the coefficient of thermal expansion (CTE) of Zr0.5Hf0.5VPO7. The investigation results show that the samples are of the single cubic type with a space group of at room temperature (RT). It can be inferred that the superstructure is transformed from the 3 × 3 × 3 superstructure to the 1 × 1 × 1 ideal crystal in a temperature range between 310 K and 323 K. The CTE is measured by a dilatometer to be 0.59 × 10−6 K−1 (310 K–673 K). The values of intrinsic (XRD) and extrinsic (dilatometric) thermal expansion are both near zero. The results show that Zr0.5Hf0.5VPO7 has near-zero thermal expansion behavior over a wide temperature range. [ABSTRACT FROM AUTHOR]