Structural properties of the system m-ZrO2-alpha-Fe2O3

The existence of solid solutions in the system m-ZrO2-alpha-Fe2O3 was studied by X-ray powder diffraction, A series of samples were prepared from aqueous solutions of corresponding nitrates and subsequent heating of the obtained precipitate up to 1100 degrees C. Diffraction patterns were taken by step-scanning and determination of unit-cell parameters was performed by means of the powder-pattern-fitting methods. In the whole concentration range there exist two types of solid solution, Z and F, of the form Zr1-xFe2xO2+x, very closely structurally related to m-ZrO2 and alpha-Fe2O3 respectively. Exclusively the Z phase exists for 0 less than or equal to x less than or similar to 002. Its unit-cell parameters are different and its crystal lattice is asymmetrically distorted in relation to those of m-ZrO2. Exclusively the F phase exists for 0.99 less than or similar to x less than or equal to 1, having unit-cell parameters very similar to those of alpha-Fe2O3. In:the two-phase region, 0.02 less than or similar to x less than or similar to 0.99, the unit-cell parameters of both the Z and F phases did not change, while the fraction of the F phase increased and the fraction of the Z phase decreased as x increased. The terminal solid solubility limits at room temperature, (2.0+/-0.3) mol% of alpha-Fe2O3 in m-ZrO2 and (1.0+/-0.3) mol% of m-ZrO2 in alpha-Fe2O3 were found from the dependence of diffraction line intensities of both Z and F phases on x by extrapolation to zero intensity. The existence of solid solutions in the limiting concentration ranges were confirmed by Mossbauer spectroscopy.