Fabrication of negative thermal expansion ZrMo2O8 film by sol–gel method

Abstracts 8 film with cubic β-ZrW2O8 structure was prepared on glass substrates via the sol–gel dip coating method. The structural, compositional, morphological and thermal expansion properties of the ZrMo2O8 film were studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The bonding strength of the as-prepared films was measured by scratch testing. The results indicated that crystalline ZrMo2O7(OH)2(H2O)2 precursor powders changed into amorphous gel as the coordination reaction of citric acid and polyvinylpyrrolidone (PVP) with metal ions. Cubic β-ZrMo2O8 film consisting of ball-like particles could be obtained after annealing the gel film, and the bonding strength decreased from 27.8 N (gel film) to 8.7 N (β-ZrMo2O8 film). The room temperature lattice parameters of resulting cubic β-ZrMo2O8 film are a = b = c = 8.976 Å, and this film exhibited excellent negative thermal expansion (CTE = −8.66 × 10−6 K−1) property from room temperature to 430 °C.