o-ZrW_(1.6)Mo_(0.4)O_8: A Novel Orthorhombic Intermediate Phase Formed During the Synthesis of the Negative Thermal Expansion Cubic ZrW_(1.6)Mo_(0.4)O_8 Material by the Precursor Dehydration Route

摘要

The mechanism of the precursor dehydration route was revealed for the synthesis of NTE c-ZrW_(1.6)Mo_(0.4)O_8. The hydrate precursor was dehydrated at 473 K and transformed to a NTE cubic compound above 800 K. A novel intermediate phase o-ZrW_(1.6)Mo_(0.4)O_8 occurs between the temperature range of 573? 800 K. The XRD pattern of novel intermediate was refined with the structural model of LT-ZrMo_2O_8 by using Rietveld method. The residuals are R_(wp) = 7.80% and R_p = 5.79%. The space group is Pmn2_1 and the lattice parameters are a = 0.5917(4) nm, b = 0.7273(4) nm, c = 0.9148(6) nm, and Z = 2.