The use of concentrated solar energy as a source of heating has opened up further opportunities for producing high-temperature oxides and compounds based on them.The usual way of producing fused oxides is by electric-arc melting and induction methods; to a lesser extent plasma and radiant heat are used. It is clear that the "cold" crucible and radiant methods can be used successfully to produce pure materials since these methods eliminate contamination of the materials by impurities. A detailed comparison of various methods of high-temperature processes for fused materials has been given in [1].Melting in solar furnaces has such advantages as the simplicity of the process, the absence of contamination of the material by the crucible, the completeness of the reaction in the melt during the synthesis of compounds, the cleaning which accompanies the fusion as a result of evaporation of impurities, etc, It should be noted that the method of producing fused oxides in a solar furnace is not usual but its advantages suggest that it should be widely used. Not least important is the fact that the use of the sun' s energy eliminates the consumption of fuel and energy resources and reduces atmospheric pollution.The present article summarizes the first results from a synthesis of calcium zircanate in solar furnaces with concentrator diameters of 2 and 3 m.At present, calcium zirconate is of particular interest. This compound is superior to stabilized ZrO 2 with respect to several parameters, including electrical resistivity.The synthesis of calcium zirconate in the solid phase was the subject of studies in [2][3][4][5][6][7]. It was shown that the properties of the material and articles made from it are mainly determined by the completeness of the reaction between the original calcium and zirconium oxides in a stoichiometric ratio. The presence of unreacted CaO and ZrO 2 degrades its mechanical, chemical, and electrical properties. The presence in the specimens of free oxygen has a deleterious effect on the sintering, lowering the degree of compaction of the articles [6]. At the same time it is well known that the synthesis of the compounds can be achieved almost completely in the melt [2, 8]. This is particularly true of the high-temperature compounds based on oxides whose solid-phase synthesis frequently requires a combination of high temperatures and an oxidizing medium and it is not always possible to provide this in practice.We used CaO, analytically pure grade and ZrO2, pure and particularly pure grades, for the preparation of the specimens. The fusion was carried out in water-cooled crucibles or on substrates; no trace of any interaction were observed between melt and crucible. The specimen was fused right through by this method; when there was a thin layer of unfused product, the specimens were fused again. The whole process took 1-3 min and the duration of the fusion was determined by the amount of material to be melted.Depending on the purity of the original materials, the color of the specimens changed from a braw...
Large-area semiconductor detectors are used to measure low-intensity beta radiation. Conventionally, a large number of semiconductor detectors are joined to form a single mosaic system [i]. However, such systems are characterized by shortcomings which limit their wide use. The most important shortcomings are: the radiometric properties of the individual modules are not identical (so that the analysis of the total amplitude spectrum is very complicated), the coefficient of covering the entry windows is small (usually ~ 0,5), a large number of independent preamplifiers and complicated electronic equipment must be used, etco Building a semiconductor detector on a single crystal of large diameter is therefore an urgent problem in applied nuclear physics. We describe below silicon semiconductor detectors with a diameter of 90 mm with hole-type conduction; the detectors had been grown with the Czochralski technique and had a specific resistivity % = 12 ~ .cm and a carrier lifetime T = 50 ~sec.Lithium was diffused to a depth of i00 ~m into 3-rmm-thick plates at p = 1.33 mPa and T = 500~Step-like drift conditions were selected to satisfy thermal balance conditions under which self-overheating of the crystal by the inverse current was prevented (see Table i). Such multistep drift conditions with a gradual increase in voltage and temperature, combined with smooth drifting in the last stage, provided for a uniform compensation of the sensitive region of the semiconductor detectorwith a sufficiently high pi value: according to measurements madewith the phase--frequency technique of [2], pi E 50 k~,cm. The depth of the compensated regionwas W=700-750 Dm. T-shape geometry (see Fig. i) was obtained by a subsequent chemical treatmentof the finished p--i-n structure. In designing the semiconductor detector, themechanical strength was preserved, the junctionswere reliably shielded and could be deactivated, the influence of the intrinsic radioactive background of the device materials was reduced, and the operation of the devicewas simple. Accordingly, a crystal thickness of 3-3.5mmwaschosen, the housing wasmade fromlucite having an intrinsic background smaller than that of aluminum, copper, or iron and a compound on thebasis of EKLB-10B epoxy resin was used for the passivating shield. Electric contacts to the front surfaces of the plate were applied by sputtering nickel in vacuum to a thickness of 30 nm. The finished detectors have a very thick diffusion region and mechanically stable, firm electric contacts. In this way the sensitive region and the working junction of the semiconductor detector are protected from mechanical and chemical damage in studies made with poured-on or pressed-on beta-emitting samples. Furthermore, it is possible to repeatedly clean the surface of the entry window of the semiconductor detector from possible radioactive contamination while the experiments are going on. Other detector designs with thin entry windows do not have this advantage. These properties facilitate the use of our semiconductor detector...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.