JOURNAL OF MATERIALS SCIENCE 18 (1983) 3679-3685 Formation of cadmium stannates studied by electron spectroscopy F. GOLESTANI-FARD, T. HASHEMI Materials and Energy Research Centre, PO Box 41-2927, Tehran, Iran K. J. D. MACKENZIE Chemistry Division, DSIR, Private Bag, Petone, New Zealand C: A. HOGARTH Physics Department, Brunel University, Uxbridge, Middlesex, UK The formation of CdSnOa and Cd2Sn04 from cadmium and tin oxides in closed vessels was studied over a range of temperature by thermal analysis, X-ray powder diffraction and electron spectroscopy. The results, presented in diagrammatic form, enable suitable reaction conditions to be chosen for the formation of either stannate in the monophase form. ESCA and SIMS examination of the reactants and products indicates that the commercial CdO starting material contains small amounts of carbonate and suboxide impurities, which however have no effect on the formation of the final product. Electron spectroscopy also indicates that the cadmium stannates, once formed, are significantly more resistant to atmospheric carbonation or hydration than is the parent CdO. 1. Introduction Conducting oxide materials are of special interest for a number of solar energy conversion applica- tions. One promising system recently under investigation is CdO/SnO2. Two distinct com- pounds, Cd2SnO4 and CdSnO3 exist within the CdO/SnO2 system [1, 2]. Dicadmium stannate is reported to have high optical transmission over the visible range as well as high conductivity [3, 4]. Potential usefulness of this compound in transpar- ent electrode and heat mirror applications has been indicated by many authors [5-12]. Mono- cadmium stannate is reported to have promising photoelectrochemical properties [3,13]. During the preparation of either of the cad- mium stannates as monophase by solid state reac- tion, the desired product may be contaminated both by the reactant oxides and the other stannate [14, 15], which contamination can influence the optical, electrical and photoelectrochemical proper- ties of the product. In order to prepare either CdaSnO4 or CdSnO3 in monophase form by solid state reaction, precise knowledge of the formation and thermal stability of these compounds is essen- 0022-2461/83 $03.00 + .12 tial. To gain this information, a detailed study was made of the reactions by X-ray diffractometry and thermal analysis. More detailed structural informa- tion concerning the cadmium stannates can be gained from recently-developed analytical tech- niques such as ESCA (or X-ray photoelectron spectroscopy) and SIMS (secondary ion mass spectrometry). ESCA has been extensively used in studies of inorganic compounds [16, 17], and although the literature data on ternary compounds [18] are still sparse, it is clear that this powerful technique can provide useful structural informa- tion as well as surface analysis of ternary oxides. Some data on the binding energies in CdO and SnO2 are reported in the literature [17-24]; because of its relatively greater importance, CdO has received more attention, but nonconcordant data have been reported [20, 22, 24]. No ESCA data for cadmium stannates are available in the literature. The present paper reports some of the results of an investigation of the CdO/SnO2 system which forms part of a joint research programme between the Materials and Energy Research Centre and Brunel University. 9 1983 Chapman and Hall Ltd. 3679