A new anatase-type phase in the system Mg-Ta-O-N

摘要

Magnesium doped tantalum oxynitrides were prepared by ammonolysis of amorphous mixed oxides. An orange colored anatase-type phase kith the composition Mg0.05Ta0.95O1.15N0.85 was found. It is metastable and undergoes a phase transformation to a baddeleyite-type phase between 900 and 1000 degrees C. X-ray diffraction measurements indicate spacegroup I4(1)/amd with lattice parameters a = 391.986(6) pm and c = 1011.19(3) pm. A possible anion ordering was examined by theoretical methods and neutron diffraction experiments. In addition, anosovite-type (Ti3O5) phases MgxTa3-xO3xN5-3x; 0 <= x <= 0.3 were obtained. The electronic spectra of all phases were investigated by UV/vis spectroscopy. (c) 2006 Elsevier Inc. All rights reserved.