| 摘要 |
<p>Prodn. of chemically pure Te dioxide (I) by oxidn. of metallic Te (of commercial quality) is achieved by adding Te with a particle size of >1 mm, pref. 2-5 mm, to pure conc. sulphuric acid (II) at a temp. >=100 degrees C and up to the b.pt., pref. 180-200 degrees C. When the reaction is complete, the supernatant liq. is decanted well from the white crystal slurry of basic Te sulphate, which, without further purificn., is added to sufficient caustic alkali, pref. NaOH soln. to convert it to alkali tellurite, with simultaneous dissoln. The soln. is filtered, then the filtrate is diluted with an equal vol. of precipitant, pref. water. (I), which is pptd. quantitatively, is washed with distilled water, filtered and dried. In an example, 99.9% pure Te(0.04% Se) of particles size 1-3 mm was heated with (II) at 200 degrees C, cooled, decanted, dissolved in 20% NaOH soln., treated with water, washed and dried. Pure (I) (under 0.01% SO24-; no detectable Se) was obtd. in 97% yield. (I) is used in the prodn. of telluride semiconductors, Cd tellurite for utilisation of solar energy and selective light transmission and in tellurite for heat-sensitive semiconductor resistors with negative temp. coeffts. It is not necessary to use very fine Te powder, so that the formation of vapour or dust contg. Te is suppressed.</p> |
