Low-temperature stabilization of tetragonal zirconia by bismuth

Low-temperature (400-800 degrees C) stabilization of tetragonal zirconia, prepared by a hydroxide gel route and low-temperature annealing, has been achieved by partial substitution of Zr4+ with Bi3+. XRD and Raman spectroscopy have been used for characterization of the doped zirconia powders as well as for identification of the crystal symmetry. XPS data provide evidence of the presence of Bi(III) and of a small amount of a lower Bi sub-oxide. A phase transition from the tetragonal structure of zirconia to the monoclinic phase takes place above 800 degrees C. The grain size dependence upon the annealing temperature has been evaluated using the Scherrer equation. Particle morphology and size have been directly imaged with the aid of SEM.