Effects of Ce Doping on Phosphor Characteristics of CaGa₂S₄:Eu

Abstract

Luminescence characteristics of Ce and Eu co-doped CaGa2S4 have been investigated for the first time. All co-doped samples showed the emission from Eu centers having a peak energy of ∼2.22 eV and they were found to have quantum efficiency values less than 30% for Eu doped sample under 441.6 nm excitation. Thermoluminesence was observed for all co-doped samples. These facts seem to indicate the existence of traps, which may mask the energy transfer from Ce to Eu in co-doped samples. Analyses of the measured transient thermoluminescence (TTL) showed two activation energies, ∼0.2 eV and ∼0.9 eV for most co-doped samples. A model where one trap level participates in two different activation processes is proposed to explain these two activation energies.

A note on X-ray spherical wavefields in the Laue case for perfect crystals

“…In Laue case B (2), where the s-line is located below both branch points, the similar treatment briefly described in Appendix A is applicable and the same results are obtained as those tabulated in Table 1. The present results are also the same as those for Laue cases A(1) and A(2), which were derived by Kato (1968a Upper row: U 0 ðþÞ or U g ðþÞ; lower row: U 0 ðÀÞ or U g ðÀÞ.…”

“…3. In Laue cases A(1) and A(2), the s-line is located between the two branch points as in the conventional case where the real part of the crystal structure factor is large, and the previous treatment by Kato (1968a) and Saka et al (1972a) is straightforwardly applicable and yields the same results as those in Kato (1968a). (Descriptions of this treatment have been omitted here.)…”

Photoluminescence spectra of rare earth doped CaGa2S4 single crystals

“…However, most of the researches on these materials are carried out using polycrystalline thin films or polycrystals, so that physical characteristics fundamental for the single crystal have not been fully clarified. Photoluminescence spectra of Ce and Eu doped crystals gave broad PL lines similar to those already described in previous papers [5,6]. Here, only the results of photoluminescence measured using CaGa 2 S 4 single crystals doped with the respective elements (Pr 3C , Tb 3C , Er 3C , Tm 3C ) successfully grown by the melt method are presented.…”

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

“…According to Kato (1968), the integral intensity R for a' set-up in symmetric Laue geometry oscillates as…”