CeO_2–YO_(1.5)–NdO_(1.5) system: An extensive phase relation study

摘要

The sub-solidus phase relations in the CeO_2–YO_(1.5)–NdO_(1.5 )system have been studied. About 45 compositions in the series Ce_(1-x)(Y_(0.70)Nd_(0.30))_xO_(2-0.5)_x, Y_(1-x)(Ce_(0.50)Nd_(0.50))_xO_(1.5+0.25x) and Nd_(1-x)(Ce_(0.55)Y_(0.45))xO_(1.5+0.275x) were prepared and characterized by powder XRD. In the Ce_(1-x)(Y_(0.70)Nd_(0.30))_xO_(2-0.5x) series, there was a gradual transformation from the defective F-type cubic lattice to an ordered C-type phase with increasing x, whereas in the Y_(1-x)(Ce_(0.50)Nd_(0.50))_xO_(1.5+0.25x) series, the C-type cubic lattice of yttria was retained over the entire range. In the Nd_(1-x)(Ce_(0.55)Y_(0.45))_xO_(1.5+0.275x) system, the compositions with NdO_(1.5) content greater than 95 mol% showed coexistence of hexagonal, monoclinic and cubic phases. A biphasic region of monoclinic and C-type cubic phases was observed as NdO_(1.5) decreases from 90 to 70 mol%. All the compositions below 70 mol% NdO_(1.5), were found to be C-type cubic solid solutions. The phase relations are distinctly characterized by an extensive range of cubic solid solutions, stable under the slow-cooled conditions. To the best of our knowledge, this is the first detailed sub-solidus study reported in CeO_2–YO_(1.5)–NdO_(1.5) system.