Order–disorder transition and thermal conductivity of (Yb_xNd_1−x)₂Zr₂O₇ solid solutions

Abstract

X-ray diffraction, transmission electron microscopy and a laser-flash method were used to investigate the order–disorder transition and thermal conductivity of (Yb _x Nd_{1− x} )₂Zr₂O₇ (0 ≤ x ≤ 1.00) solid solutions. The structures were found to be pyrochlore-type for 0 ≤ x ≤ 0.25, defect fluorite for 0.45 ≤ x ≤ 1.00 and a mixture of these at 0.30 ≤ x ≤ 0.40. The thermal conductivities of (Yb _x Nd_{1− x} )₂Zr₂O₇ first gradually decrease with increasing temperature, and then increase slightly above 800°C due to the increased radiation contribution. YbNdZr₂O₇ has the lowest thermal conductivity due to the reduced cation mean free path at the compositional combination of equal molar Yb³⁺ and Nd³⁺ cations.

Keywords:

• phase transitions
• structure analysis
• order
• disorder
• thermal properties

Acknowledgements

The authors would like to thank the financial support by the Program of Excellent Teams in Harbin Institute of Technology (HIT) and the Start-up Program for High-level HIT Faculty Returned from Abroad.