Characterization of Sintered Mixed Oxides by Photothermal Microscopy

Abstract

A new photothermal microscopy device is presented and used to map the thermal diffusivity of mixed oxides. The particular cases of UO2 + 10 %Gd2O3 andUO2 +7.5%Dy2O3 are discussed, showing how to determine the homogeneity of theprepared samples, distinguish interdiffused oxides from mixed oxides, recognize and characterize clusters, and determine the relative abundance of different species and its spatial distribution. Histograms can be generated that provide a quantitative determination of the homogeneity. Adding an independent determination of the thermal diffusivity as a function of the composition made in bulk material allows the conversion of the diffusivity map into a concentration map, providing direct quantitative determination of the homogeneity and spatial distribution in concentration units. The new device can be added as an accessory to an optical microscope entering through a standard C mount camera port. Two semiconductor lasers within the viewing spectroscopic window of any microscope (650 nm wavelength for the pump and 785 nm for the probe) that were coupled to a single-mode fiber were used, and the reflected signal was collected using the same fiber. With this construction, the resulting equipment was robust and reliable.