Mechanical and thermal properties evaluation of Eu2O3-Gd2Zr2O7 ceramics served as potential neutron absorber rod

Rare earth compounds (RE2O3), typically Eu2O3 and Gd2O3, are considered as absorbing materials due to their long chain neutron absorbing ability and high efficiency of neutron absorption. In this paper, a specifically designed xEu2O3-(1-x)Gd2Zr2O7 (x=0.6, 0.7, 0.8, 0.85) composite ceramics with excellent thermal properties were synthesized through direct thermal decomposition reactions followed a high-temperature sintering method under vacuum conditions. X-ray diffraction (XRD) and Raman spectroscopy analysis indicated that the obtained ceramics consisted of monoclinic Eu2O3 and fluorite Gd2Zr2O7 phases. The hardness of xEu2O3-(1-x)Gd2Zr2O7 ceramics (x=0.8, 0.85) have no significantly changes in the test temperature range (25-350 °C). The thermal expansion coefficients (TECs) (7.3-10×10-6 K-1) are lower than Dy2TiO5 (9.3-10.4×10-6 K-1), and the thermal expansion rate changes linearly with the increase of temperature, which indicates that the xEu2O3-(1-x)Gd2Zr2O7 ceramics exhibit excellent high temperature phase stability. Furthermore, the range of thermal conductivities is from 0.96 W·m-1·K-1 to 2.02 W·m-1·K-1 (25-800 °C), which is higher than Dy2TiO5 (0.27-0.55 W/m·K, 220-650 °C). Compared with the state-of-art Dy2TiO5 ceramics, xEu2O3-(1-x)Gd2Zr2O7 have superior thermal properties and are therefore expected to be the next generational of neutron absorbent materials used in ash rod.