Some crystallographic considerations on the novel orthorhombic ZrO2 stabilized with Ta doping

Some crystallographic considerations on the novel orthorhombic ZrO2 (o-ZrO2) stabilized at ambient conditions by Ta substitutional doping are presented. Specifically, how the Ta-doped o-ZrO2 was observed for the first time by conventional X-ray diffractometry (XRD) is reported, after which the ab initio and non-ab initio procedures used to resolve its crystal structure are detailed. The crystal structure is then explicitly reported (i.e., space group and cell parameters, as well as atomic positions of the asymmetric unit). It is also shown that this novel Ta-doped o-ZrO2 has a crystal structure similar, but not identical, to the high-pressure o-ZrO2. Additionally, given that the crystal structure of the Ta-doped o-ZrO2 is identified as being a symmetry-breaking distortion of the typical tetragonal ZrO2 (t-ZrO2) stabilized with the commonest dopants, a complete analysis is also made of the structural distortions relating both the Ta-doped o-ZrO2 and the high-pressure o-ZrO2 to the t-ZrO2. Finally, a justification for the apparent greater immunity of the Ta-doped o-ZrO2 to aging is provided.