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As the organic laser materials, tetrakis europium β-diketone chelates have been prepared by using several β-diketones which contain a trifluoromethyl group as well as an aromatic hydrocarbon such as naphthalene, phenanthrene, anthracene, or compounds substituted at the para position of a benzene ring. Absorption and excitation spectra, fluorescence quantum yields, and fluorescence lifetimes of these europium chelates have been obtained. Except for the europium chelates of β-diketones derived from benzylideneacetone (EuBZDTFA) and anthracene (Eu9ATFA), these europium β-diketone chelates show strong red fluorescence characteristic of Eu3+ ion at room temperature both in solution and in crystalline powders. EuBZDTFA does not fluoresce till the temperature is lowered to about -80°C, and Eu9ATFA never fluoresces even at the liquid nitrogen temperature.

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Red light emitting electroluminescent phosphors in the (Zn,Cd)(S,Se):Cu system were investigated. The best red electroluminescent phosphor is obtained by firing (0.9Zn,0.1Cd)(0.1S,0.9Se) adding Cu, 5 x 10 -3 g-atom/mole and the same coactivator concentration at 1000 ~ N ll00~ Electroluminescent and photoluminescent properties of phosphors of various composition were interpreted by curves illustrating the energy level variation with composition in solid solution, which is obtained by considering nearest-neighbor effects, and a temperature quenching factor in electroluminescence. From similar considerations, the variation of luminescent properties of phosphors of given composition, containing given luminescent centers, can be predicted, and the critical frequency of excitation when developing electroluminescent phosphors of a given color is presented.A (Zn,Cd) (S,Se) system as red light emitting electroluminescent (EL) phosphors has been developed for a part of its composition by Palilla and Baid (1), Matsuo et al. (2), Mironov and Markovskii (3), and Kolomoitsev et al. (4) in the course of our investigation, and earlier by Hegyi etal. (5), Larach et al. (6), Gelling et al. ( 7), and others, but it seems that a unified discussion on firing condition and EL properties has not been achieved. For example, the optimum firing condition differs from composition to composition, and parameters involved in EL characteristics vary with composition. Thus a question arises, "how shall we expect the possibility of (Zn,Cd)(S,Se) as long wavelength light emitting phosphors?" Solid solutions have been extensively prepared recently to change energy gap continuously for the purpose of matching the exciting or the emitting energy.In this system, a knowledge about the impurity energy level variation with composition as well as about the energy gap variation is indispensable, for the former is undoubtedly very sensitive to optical and electrical properties.In this paper we tried to give a systematic discussion on the above problem, and to give basic considerations on the impurity energy level variation in this system in connection with them.