On the thermal expansion and crystallography of cubic (C) and monoclinic (B) forms of Gd2O3 in the temperature range 20 to 900°C

Thermal expansion coefficients of B-form (monoclinic) and C-form (cubic) Gd₂O₃ have been measured in the temperature range 20 to 900° C, by X-ray diffractometry. The thermal expansion coefficients of both cubic and monoclinic material are linear in the temperature range studied. The expansion of monoclinic material is, however, very anisotropic, and the minor axis of the thermal expansion ellipsoid is not parallel to the edge of the primitive cell to which Gd₂O₃ has been assigned. It is noted that the anisotropy in expansion behaviour of this material indicates that anisotropic growth probably occurs during irradiation.