TIXTA1-X(O,N)(Y) PHASES FORMED BY AMMONOLYSIS OF TI-TA GELS - PREPARATION OF AN ANATASE-TYPE SOLID-SOLUTION PHASE TIXTA1-XO1-X, THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.87(XN1)

Phase formation in the system TixTa1-x(O, N)(y) has been studied by am monolysis of Ti-Ta gels prepared by the sol-gel technique, at temperat ures between 600 and 1000 degrees C. The observed phases were characte rised by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis. A monophasic oxynitride wi th composition TixTa1-xO1+xN1-x and with the anatase type structure wa s prepared at 600-650 degrees C for 0.52 less than or equal to x less than or equal to 0.87. The structure was verified for the composition Ti0.68Ta0.32O1.68N0.32 (x = 0.68) by the Rietveld method (R-F = 30%) u sing CuK alpha(1) XRPD data. Electric conductivity and magnetic suscep tibility measurements showed semiconductor and temperature-independent paramagnetic behaviour, respectively. A NaCl-type phase was obtained for 0.52 less than or equal to x less than or equal to 1 at 900-1000 d egrees C. Its unit-cell volume varied both with metal composition and preparation temperature. Ta4N5- and Ta5N6-type phases were obtained fo r x less than or equal to 0.34 at 1000 degrees C. Their unit-cell volu mes decreased with increasing x, implying that Ti is incorporated in t he two types of structures. (C) 1997 Elsevier Science Limited.