Abstract
The effect of 28 GHz microwave irradiation was investigated on the optical properties of stannic oxide (SnO2). During microwave irradiation, the temperature of SnO2 rose rapidly and reached 1400°C within a few minutes. After microwave irradiation, commercial whitish green SnO2 turned to pale claret one. X-ray diffraction analysis did not reveal any phase changes or differences in lattice parameters as compared with those of SnO2 conventionally heated (1400°C, 43.2ks). Diffuse reflectance spectroscopy detected the absorption peak of claret SnO2 obtained by microwave irradiation in the range of 450-650nm. The same absorption was detected in SnO2 heated conventionally (1400°C, Os), but after annealing the claret sample turned to white one. On the other hand, microwave-irradiated sample maintained the color after long period annealing. From the X-ray photoelectron spectrometry, we found that the binding energy of Sn in claret SnO2 obtained by microwave irradiation shifted to a lower level than that of white SnO2.
