electron microscopy and energy dispersive spectroscopy. ... e.g., In3+, Sn4+ and O2-. .... two cations, would be compensated by entrapping O ... the lattice sites of In2O3 also are lost. ... point of view, this would cause the formation of holes.
Optical properties of plasma sprayed semiconducting oxides M. Tului, F. Arezzo, Centro Sviluppo Materiali, Rome/I and L. Pawlowski, ENSCL, Lille/F Optical selective surfaces, i.e., surfaces with optical properties varying according to the frequency of the impinging radiation, have been exploited in several technical fields. These surfaces consist generally of doped semiconducting films, such as mixed oxides of Indium and Tin as well as Aluminium and Zinc. Thay are currently obtained by physical vapour deposition or sol-gel techniques. The present work aimed at demonstrating that coatings retaining optical selectivity can be obtained also by plasma spraying. Powders of Indium Tin Oxide (ITO) were prepared by an agglomeration technique and sprayed with a plasma torch under air and inert gas atmospheres. Both powders and coatings were characterised by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Optical reflection coefficients of the coatings were determined in the wavelength range 0.3-20 µm, i.e., in the visible and in the infrared regions of the spectrum. The experimental results indicated that it was possible to deposit, by plasma spraying, coatings possessing optically selective properties. 1
Introduction
Optical selective surfaces are widely used in several industrial applications, ranging from antireflective coatings up to solar cells [1]. Surfaces should present low emissivity for wavelength Ȝ in the middle and far IR (Infra Red, 0.7
