Preparation and properties of negative thermal expansion zirconium tungstate thin films deposited by radio frequency magnetron sputtering

Zirconium tungstate (ZrW2O8) thin films were deposited on quartz substrates by radio frequency magnetron sputtering followed by annealing at various temperatures. The effects of post-deposition annealing temperature on the phase, morphology and negative thermal expansion properties of the ZrW2O8 thin films were investigated. X-ray diffraction data confirmed that the as-deposited ZrW2O8 films were amorphous, and crystalline ZrW2O8 films could be obtained at high annealing temperature. Trigonal ZrW2O8 films could be prepared at 740 C and cubic ZrW2O8 films could be prepared at 1200 C. The surface morphologies of the ZrW2O8 thin films were evaluated using scanning electron microscopy. The results indicated that amorphous ZrW2O8 films were uniform and dense, and the grain size of the crystalline ZrW2O8 films became larger with increasing annealing temperature. The resulting cubic ZrW2O8 films showed negative thermal expansion, the average value of thermal expansion coefficient being -8.18 x 10-6 K-1 in the temperature range 15-700 C. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)