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Optical absorption spectra were measured in undoped and Fe- or Ni-doped single crystals of CuGaS2 grown by the chemical vapor transport technique. Chemical analysis of Fe concentration by absorption spectrophotometry and optical characterization by absorption and photoluminescence(PL) spectroscopy in these materials revealed that the main trace impurities which darken undoped crystals are Ni and Fe. The excitation spectrum of the infrared PL due to Fe3+ was also measured. From this, the 1.8 eV peak of the strong absorption band introduced by trace Fe impurities was interpreted in terms of the transition from the valence band to the dangling bond state hybridized with 3d orbitals.

The ion-exchange properties of α-zirconium phosphate have been investigated for the H+–[Co(NH3)6]3+ system. The ion-exchange process was examined by means of the variation in the pH values of the supernatant. α-Zirconium phosphate loaded with hexaamminecobalt(III) was also characterized by chemical analysis, X-ray diffractometry, infrared spectroscopy, and thermal analysis. In spite of the steric hindrance in the crystal structure of α-zirconium phosphate, the ion exchange proceeded gradually. About 30% of the hydrogen ions in α-zirconium phosphate were replaced by hexaamminecobalt(III). The interlayer distance of the exchanger expanded from 0.76 to 1.12 nm.

The ion-exchange isotherms for the NH4+–Li+ system on crystalline zirconium phosphate have been determined at 25 °C, and the structural change and water content of the exchanger have also been investigated by means of X-ray diffraction and thermal analysis. The isotherms showed that the ion-exchange reaction took place in one stage, that is, the ammonium-form was converted into the lithium-form in the forward process, and vice versa in the reverse process. However, the results of X-ray diffractometry indicated that the ion-exchange reactions proceeded in three stages in each direction. The isotherms also showed a hysteresis loop. This phenomenon can be ascribed to the difference in the water content of the exchangers, because the X-ray powder patterns of the exchanger phases were essentially identical at similar ionic mole fraction of lithium ion in the exchangers of the two processes.

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The ion-exchange behavior of the ammonium ion on crystalline zirconium phosphate (c-ZrP) was studied by pH titration and X-ray powder diffraction. The ion-exchange capacity of c-ZrP was 4.4 meq/g in an acidic solution and 6.6 meq/g in an alkaline solution. At an exchange of 66% the Zr(NH4PO4)1.33(HPO4)0.67·H2O phase was present and at an exchange of 100% Zr(NH4PO4)2·H2O phase was present. The forward and backward titration curves exhibited a hysteresis loop. This results from the presence of the different phases in the titration of each direction. Through the ion-exchange cycle, the crystallinity of c-ZrP was maintained.