STOICHIOMETRIC DEVIATIONS ALONG AN INGOT OF CUGASE2

Citation
T. Martin et al., STOICHIOMETRIC DEVIATIONS ALONG AN INGOT OF CUGASE2, Advanced materials for optics and electronics, 8(3), 1998, pp. 147-155
Citations number
18
Categorie Soggetti
Material Science",Optics,"Engineering, Eletrical & Electronic","Chemistry Applied",Chemistry
ISSN journal
10579257
Volume
8
Issue
3
Year of publication
1998
Pages
147 - 155
Database
ISI
SICI code
1057-9257(1998)8:3<147:SDAAIO>2.0.ZU;2-M
Abstract
The dependence of the structural parameters on compositional deviation s of CuGaSe2 has been studied. These deviations have been induced alon g an ingot by a single fusion of the components at 1150 degrees C and subsequent slow cooling in a stationary ampoule in a vertical furnace. All along the sample a single chalcopyrite phase is present and a com positional gradient along the ingot was found by energy-dispersive ana lysis of X-rays (EDAX) measurements, the upper part being rich in Ga ( series B) and the lower part in Cu (series A), with Cu/Ga ratios of 0. 95 and 1.1 respectively. A hypothesis of the existence of two phases i n the melt is proposed to explain these facts. The unit cell parameter s, anion displacement and Cu and Ga occupation numbers in their sublat tices were analysed by X-ray powder diffraction and Rietveld refinemen t methods. In series A the occupation numbers are near stoichiometry, while in series B a Cu defect appears. In both series, changes in unit cell parameter are related to changes in Cu content, suggesting the p resence of a fraction of Cu ions either as interstitials or at Ga site s when Cu is in excess, or of Cu vacancies in its sublattice when ther e is a Cu deficiency. (C) 1998 John Wiley & Sons, Ltd.