Microanalysis of bismuth indium selenide thermoelectronic materials by X-ray fluorescence spectrometry with reference assays of indium

Abstract

Screening of a small area on the natural cleavage face of a layered single crystal was used for X-ray fluorescence spectrometric (XRF) assays. A precise determination of indium (within the range 1–8% m/m) in Bi_2–xIn_xSe₃ single crystals was based on the calibration of the net intensity of the In Kα_1,2 line with the use of the results of extraction–photometric analysis after decomposition of the crystal chips exposed to X-rays. In acetate buffer medium (pH ≈ 4.0, V_aq= 40 cm³) and with an adequate excess of quinolin-8-ol and thiosulfate (masking of bismuth), the tris(quinolin-8-olato)indium(III) chelate was completely transferred into 10 cm³ of chloroform. The absorbance of the chloroform extract was measured at 400 nm against a blank extract. For calibration of the X-ray spectrometer a computer program was written using a simplified least-squares method of linear regression for both variables subject to experimental error. The XRF method allows the selection of a piece of crystal suitable for measurements of physical parameters.