The hydrothermal synthesis of binary solid solutions of inorganic phosphors and photoconductors is described. This method depends on the increased reactivity between the components and ease of crystal growth in an aqueous solution maintained at high temperature under a confining pressure. The hydrothermal method offers the advantages of a sealed system and easily reproducible experimental conditions. Solid solutions of ZnS-HgS, CdS-HgS, and ZnS-CdS have been prepared by this method. Results of optical absorption measurements, x-ray analysis, microscopic studies, and the spectral photoresponse of the solid solutions formed are presented.

The electroluminescent brightness of single phosphor particles is studied microscopically in liquid dielectric cells. A simple visual technique in conjunction with a microscope permits one to analyze the brightness distribution within and among electroluminescent particles. Some experimental results are presented on the nonuniformity of the emission, the influence of ball milling and acid etching on the brightness, the improvement of brightness by particle separation, the analysis of the integrated light output as a function of the processing temperature, and the brightness changes due to particle orientation, contact, and irradiation.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-06-02 to IP

Ball milling, followed by displacement washing, permits a distinction to be made between lattice chloride and internal surface chloride as parts of volume chloride. The surface area, which is determined by gas adsorption methods, increases rapidly in the beginning and then in a linear manner as a function of milling time. The extent of linearity between surface area and milling time is considered to be a measure of crystallinity. The data indicate that the maximal amount of lattice chloride becomes incorporated at a processing temperature near 700°C after a processing time of 2 hr. Zinc sulfide gradually loses its ability to luminesce under ultraviolet (u.v.) irradiation during milling; the logarithm of the luminescence emission is about proportional to the newly formed surface. It appears that the luminescence centers consist of lattice regions of about 0.2 µ in diameter, as is indicated by the observed minimal size of luminescent particles. The luminescence emission of milled samples can be restored by reprocessing, although the degree of restoration is highly sensitive to impurities introduced during milling.

A concentration cell procedure, based on the method of Furman and Low, is employed to study chloride retention in zinc sulfide powders. Amounts of 0.001% by weight of chloride in 1 g of zinc sulfide can be determined quantitatively. Zinc sulfide powders with physically admixed or coprecipitated chloride are processed in open boats with variations in firing time and temperature; the retained chloride is determined. The chloride retained after displacement of surface chloride is defined as “volume chloride.” It is found that the retention of volume chloride in zinc sulfide is similar whether zinc chloride or sodium chloride is used as the flux; a peak concentration is observed in both cases after processing near 500 °C. The experimental results are interpreted and found significant in elucidating the mechanism of the incorporation of chloride into zinc sulfide powder during phosphor preparation.

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