Crystal structure and negative thermal expansion of solid solution Lu₂W_3-xMo_xO₁₂

Jie Peng1,2), Xin-zhi Liu3), Fu-li Guo4), Song-bai Han3), Yun-tao Liu3), Dong-feng Chen3), and Zhong-bo Hu2) 1) Experimental Physics Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2) College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, Beijing 100049, China 3) China Institute of Atomic Energy, Beijing 102413, China 4) College of Chemistry, Beijing Normal University, Beijing 100875, China

摘 要：A new series of solid solutions Lu2W3?xMoxO12 （0.5≤x≤2.5） were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth tungstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients （TEC） of Lu2W3?xMoxO12 are determined as ?20.0×10?6 K?1 for x=0.5 and ?16.1×10?6 K?1 for x=2.5 but ?18.6×10?6 and ?16.9×10?6 K?1 for unsubstituted Lu2W3O12 and Lu2Mo3O12 in the identical temperature range of 200 to 800°C. High-temperature X-ray diffraction （XRD） data and bond length analysis suggest that the difference between W?O and Mo?O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.

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