Synthesis and dissolution kinetics of zirconia based ceramics

Abstract

In this study, an ideal Nd2Zr2O7 pyrochlore and a defect fluorite ceramic were synthesised by coprecipitation, pressing and sintering. Detailed investigations by electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and powder X-ray diffraction (XRD) were used for the characterisation of the powders. In particular both powders were found to be single phase ceramics.All batch and dynamic dissolution experiments were conducted in C(HCl) = 0.1 M at 90 °C to compare the two types of Nd-zirconia structures and the experimental approaches. A good agreement between batch and dynamic dissolution experiments was observed for the pyrochlore with a Nd-based final dissolution rate in the range between 0.84 × 10−5 and 1.95 × 10−5 g m−2 d−1. The dynamic experiments indicate a strongly incongruent preferential release of Nd from the pyrochlore ceramic at the beginning of the experiment and a close to congruent dissolution at the end of the experiment.The dissolution behaviour of defect fluorite in dynamic experiments is observed to be very similar to the pyrochlore. An incongruent dissolution during the early stages is followed by a congruent steady state. The defect fluorite steady state dissolution rate is lower than the one determined for pyrochlore.