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BaIn2S4, BaIn2S4:Ho3+, BaIn2S4:Er3+, BaIn2S4:Tm3+, BaIn2Se4, BaIn2Se4:Ho3+, BaIn2Se4:Er3+, and BaIn2Se4:Tm3+ single crystals were grown by the chemical transport reaction method. The optical energy gap of the single crystals was found to be 3.057, 2.987, 2.967, 2.907, 2.625, 2.545, 2.515, and 2.415 eV, respectively, at 11 K. The temperature dependence of the optical energy gap was well fitted by the Varshni equation. Broad emission peaks were observed in the photoluminescence spectra of the single crystals. They were assigned to donor–acceptor pair recombination. Sharp emission peaks were observed in the doped single crystals. They were attributed to be due to radiation recombination between the Stark levels of the Ho3+, Er3+, and Tm3+ ions sited in C1 symmetry.

PACS 78.55.HxPhotoluminescence spectra of Cd 1−xMnxGa2S4 mixed crystals were investigated in the composition region of 0.00 ≤ x ≤ 1.00 and in the temperature region of 6 to 300 K. The photoluminescence spectrum of CdGa 2 S 4 (x = 0.00) showed two emission bands at 594 nm (2.09 eV) and 460 nm (2.70 eV), which were attributed to be due to donor-acceptor pair recombination. The same feature of these bands was also observed for the crystals doped with 5 mol% Mn, excepting a slightly red shift and a decreasing of the halfwidth of the emission band in the longer wavelength region. For the crystals in the composition region of x ≤ 0.67, only the emission band in the longer wavelength region were observed. The photoluminescence spectra of MnGa 2S4(x = 1.00) showed a broad emission band 675 nm (1.838 eV), which is different from that of CdGa 2S4. The relative intensity of the main emission band increased in the composition region of 0.00 ≤ x ≤ 0.67 with increasing x while decreased in the region of 0.90 ≤ x ≤ 1.00. The anomalous composition dependence was connected with an occurrence of a miscibility gap of the crystal structure in that region.

The composition and temperature dependence of the band gap and the lattice constants of the MgxCd1−xSe crystals was investigated in the composition range of 0.00 ≤ x ≤ 0.46 and in the temperature range of 11 to 290 K. The lattice constants showed a composition dependence decreasing linearly with increasing composition x, and also showed a temperature dependence that the relative variation of the lattice constants with temperature is somewhat different from each other for all the crystals. The temperature dependent behavior of the lattice constants was also observed with an inverse trend in the temperature dependence of the band gaps. The temperature dependence of the band gaps was well fitted by the empirical Varshni equation for all the investigated compositions. The composition dependence of the band gaps was represented by the linear relationship of Eg(x) = 1.742 + 1.813 x for 290 K and Eg(x) = 1.828 + 1.871 x for 11 K.