Retention of Chloride in Zinc Sulfide during Phosphor Preparation

Abstract

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.

Particle Growth during Zinc Sulfide Phosphor Preparation

“…The proportionality constant is considered to contain the activation energy, which is nearly three times as high without as with the fluxing agent. They found that the increase of the particle volume with time t is constant at constant temperature, which is not in agreement with our results (8) which lead to a fib dependence, as explained in the discussion section.…”

“…The curve in Fig. (10). The anomalous peak near 1000~ is accompanied by anomalous behavior with respect to the crystal structure and the amount of retained volume chloride, ' as shown in Fig.…”

“…It was found that these s See definition of "volume chloride" in ref. (10). In t h a t case one would expect to find the largest a m o u n t in the smallest particles because of their large surface area and in those of h e x a g o n a l s t r u c t u r e because of their open structure.…”

“…The same publication (9) also describes a semi-quantitative method which was employed in the present investigation to obtain a measure of photoluminescence intensity. The determination of chloride has been discussed in some detail in a previous publication (10). This method permits one to determine quantitatively amounts of 0.001% by weight of chloride in 1 g of zinc sulfide; results have been found to be reproducible and accurate.…”

Mechanism of Flux Action in the Thermal Recrystallization of Zinc Sulfide

“…Consequently, particle growth in zinc sulfide containing sodium chloride is suggested to occur as follows. Chemical interaction between the host material and flux leads to the introduction of chloride into the host lattice at low temperatures (20). Although the exact nature of the resultant defects is not fully understood, several workers (21,22) have suggested that interstitial zinc may be formed.…”