Influence of the partial substitution of Y2O3 with Ln2O3 (Ln=Nd, Sm, Gd) on the phase structure and thermophysical properties of ZrO2–Nb2O5–Y2O3 ceramics

Abstract The low thermal conductivity, elevated phase-transformation temperature and improved mechanical properties make the ZrO 2 –Nb 2 O 5 –Y 2 O 3 system a promising candidate for thermal barrier coatings. In this study, the influences of the partial substitution of Y 2 O 3 with equimolar Ln 2 O 3 (Ln = Nd, Sm, Gd) on the phase structure and thermal properties of ZrO 2 –Nb 2 O 5 –Y 2 O 3 ceramics have been investigated. X-ray diffraction analysis indicates that these compositions consist of the pure non-transformable tetragonal phase and have an obviously higher tetragonality c / a than the binary ZrO 2 systems. Nevertheless, the partial substitution leads to a decrease in the tetragonality. The thermal conductivity measurement shows that these compositions have low and temperature-independent thermal conductivities, as well as more than 10% reduction in the thermal conductivity due to the partial substitution. Among these rare-earth oxides, Nd 2 O 3 is the most effective oxide for lowering the thermal conductivity. Their thermal conductivities well agree with a point-defect scattering model. The model predicts that the phonon scattering associated with the elastic field around a point defect makes the principal contribution to the reduction of the thermal conductivity for these compositions. This research indicates potential applications of ZrO 2 –Nb 2 O 5 –Y 2 O 3 ceramics for thermal barrier coatings as well as the need for further studies.