The Electrorefinement of Indium Through an Aluminum Alkyl Complex Electrolyte

Abstract

High purity indium metal has been prepared by electrolysis at constant potential from a mixed normalAl+normalIn complex electrolyte that contains typically 2 normalmol Alfalse(C2H5)3 and 0.06 normalmol Infalse(C2H5)3 normalper mol C6H5CH2Nfalse(CH3)3F . Based on the results of cyclic voltammetry applied to the pure Al complex electrolyte and to the mixed electrolyte, a mechanism for the cathodic and anodic steps in the electrorefinement process is proposed. This mechanism is described by the following net electrode reactionsnormalAnode In+3normalAlC2H54⊖→normalInC2H53+3normalAlC2H53+3e⊖ normalCathode 3normalInC2H52⊕+3e⊖→normalIn+2normalInC2H53It is the opinion of the authors that the false[Al2Ffalse(C2H5)6]⊖ and false[Al3Ffalse(C2H5)9]⊖ ions that are shown by NMR studies to exist in equilibrium with uncomplexed normalAlfalse(C2H5)3 and Al2false(C2H5)6 , respectively, serve merely as supporting electrolyte. The indium metal obtained by electrorefinement in a mixed normalAl+normalIn alkyl electrolyte is suitable for the synthesis and bulk crystal growth of In containing compound semiconductors. However, a further reduction of the ∼2 ppm Al contamination level is required for making the electrorefined In a useful source material for epitaxial growth processes.

Isothermal vapour-phase epitaxy of mercury-cadmium telluride (Hg,Cd)Te

“…It was concluded that, within the framework of the experimental errors, this is also valid for a solid solution of the type (Hgl_~Cd~)yTel_y(s). The quantitative analysis in [77] shows that the solid solution of HgTe and CdTe is almost ideal. Therefore, it can be supposed that in this solid solution the components are mixed as quasiregular solutions; that is, (18) where W and V are interaction constants that should be determined from the experimental data.…”

“…Assume that Cd and Tea are ideal in the gas phase, and that the chemical potential of the mercury in the gas phase can be expressed in the terms of the fugacity of pttg, from [77], as…”

“…Two values of W --VT are given in the literature: from [77], W-VT =4297.1-3.5750T cal; and from [82] W -VT = 1385 --0.8452T cal.…”

“…It is simple to express PTo2 in the following simple form PTe2 = P°,2( 1 --PHg~ 2 (30) ~,pO l According to [77,81,82] 1ogpT°e~ (atm) = --5960.2/T + 4.7191 logp°g (atm) = --3099/T + 4.920 (31) The value of Y was calculated by taking into account that the pressure at the border of the region where HgTe is solid and the tellurium-rich Hgl _yTey is liquid can be calculated using the equation 1 -K2(0) -~ngexp (42.27 41260)(32) P~r~ Pig and Equation 30 should be the same. To calculate the mercury partial pressure above the border of the HgTe solid-solution HgTe, the approximate expression [85,86] 14765.55…”

Purification of InCl3electrolyte by ion exchange

“…The methods for preparing high purity indium include ion exchange, zone melting, low halide, vacuum distillation and electrolytic refining, etc. [2][3][4][5][6][7][8][9][10] It is difficult to prepare high purity indium only by electrolysis unless several combinations of purification methods are applied. Electrorefining is a usual purification method, which can be easily scaled up.…”