Copper-Activated Zinc Sulfide Phosphors with Yellow and Red Emission

Self Cite

With increasing concentrations of Cu and A1 in H~S-fired Zn(A1)S: Cu phosphors, the emission spectrum is shifted from green to orange under 3650 A excitation. The emission of these triple sulfides consists of three sub-bands of such relative intensities that the presence of a single band is simulated. The bands have different temperature, decay, and excitation characteristics. Among other substituents, the elements Sc, Ce, Pr, and Nd are of interest, as they produce infrared stimulability even with high activator concentrations.

Section: Trivalent Substituents Other Than A1mentioning

confidence: 63%

“…The phosphors were prepared and fired in the manner described in a previous paper (3). Copper and the trivalent elements were introduced in form of several salts such as chlorides, nitrates, sulfates, etc., with equally consistent results.…”

Section: Methodsmentioning

confidence: 99%

Copper-Activated Zinc Sulfide Phosphors with Trivalent Substituents

Froelich

1953

Self Cite

“…The energy of the system is thereby reduced by approximately the energy required to ionize an electron from a covalent bond. This accounts for the increased solubility of copper in zinc sulfide in the presence of aluminum coactivator as found by Froelich (9). To summarize, the localized level above the filled valence band arises from the fact that the periodic potential of the zinc sulfide lattice in which the valence electrons move is perturbed locally in the vicinity of the activator impurity.…”

Section: Covalent ~Odel For Zinc Sulfide Phosphorsmentioning

confidence: 72%

Activator Systems in Zinc Sulfide Phosphors

Prener

Williams

1956

150

Zinc sulfide containing copper at random zinc sites was prepared by radioactive decay of Zn~< Measurements indicate that the isolated copper impurities do not contribute to luminescent emission. Using a covalent model of zinc sulfide, and recognizing the acceptor-donor nature of activators and coaetivators, association of these impurities is found and the luminescent center is identified as second or third nearest neighbor associated activator-coactivator pairs. The nearest neighbor pairs are transparent to 3650~ radiation and have many of the characteristics necessary to account for edge emission.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.7.158.43 Downloaded on 2014-12-07 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.7.158.43 Downloaded on 2014-12-07 to IP

“…For instance, in ZnS: Cu with no chemical coactivator added, Froelich reported that only about 4x 104 g-atoms Cu/mole ZnS is retained in the lattice after firing (4). In contrast, at least 9x 10 -~ g-atom Cu/mole ZnS is retained in the ZnS:Cu,A1 phosphor with orange emission (5).…”

mentioning

confidence: 99%

Investigations in the CuGaS[sub 2]-ZnS and AgGaS[sub 2] -ZnS Systems

Apple

1958

CuGaS~ and ZnS form solid solutions over the entire range with some evidence for compound formation at 33 1/3 mole % CuGaS~. Emission under 3650.~ excitation shifts from green to red with increase in CuGaS~ concentration. Samples with more than 20 % CuGaS2 do not luminesce at room temperature but, at --195~ fairly bright emission is observed with up to 95% CuGaS2. AgGaS~ is soluble in ZnS to about 5-10 mole %, above which separation of AgeS is observed. Emission under 3650A excitation shifts from the blue (0.01% AgGaS2) to yellow (10% AgGaS~).The ternary sulfides, CuGaS~ and AgGaS~, have the chalcopyrite structure which is closely related to the zinc blende structure of cubic ZnS (1). In these compounds, two different atomic species occupy equivalent lattice sites on the zinc blende lattice. In CuGaS~, a z 5.34A and c = 10.47A. (c/a = 1.96) while in AgGaS2, a = 5.74A and c = 10.26A (c/a = 1.79) (2).Because of the similarities in structure, unit cell dimensions, and bond type, the ternary sulfides may form solid solutions with ZnS. In such solid solutions, the ternary compounds would not only change the unit cell dimension of ZnS, but may also affect the observed luminescence in ZnS: Cu,Ga and ZnS:Ag,Ga phosphors. Cu and Ag are activators and Ga is a coactivator in normal ZnS phosphors with green and blue emission.The solubility of these activators in ZnS is dependent on the presence of charge-compensating ions which usually function as coactivators (3). For instance, in ZnS: Cu with no chemical coactivator added, Froelich reported that only about 4x 104 g-atoms Cu/mole ZnS is retained in the lattice after firing (4). In contrast, at least 9x 10 -~ g-atom Cu/mole ZnS is retained in the ZnS:Cu,A1 phosphor with orange emission (5). Incorporation of the larger concentration of Cu in the latter case is possible because of the simultaneous incorporation of A1 as AI~S~. In this phosphor, the A1 was added to ZnS as an oxy-salt and converted to AI~S~ during the firing process in H2S at 1100~176It is questionable whether a large amount of AI~O~ would be converted completely to ALS~ when fired in the presence of ZnS in an H~S stream. Equimolar mixtures of ZnS and AI~O~, for instance, when so fired do not yield ZnALS,, the compound expected on complete conversion of the oxide to the sulfide. In all probability, addition of A1 as the oxide or oxysalt limits the solubility of Cu because of incomplete conversion to AI~S~. However, if the activator and coactivator are added as the ternary sulfide, the oxide conversion is circumvented. Further, activator and coactivator are added in exactly stoichiometric amounts in a form which facilitates incorporation in the lattice.It is the purpose of this paper to report results of studies in the systems CuGaS~-ZnS and AgGaS2-ZnS. Of special interest will be the structural data, limits of solubility, and luminescent properties. In these systems the concentrations of Cu or Ag in ZnS far exceed those reported in the literature, and with the increased concentrations of activators incorporated ...