Samples of the Y2O3 : Eu3+(5–11 at %) phosphor with a high luminescence efficiency have been synthesized by the sol-gel method. The chemical, substructural, and optical properties of the material...

We have studied phase formation processes in the La-O-S system during La₂O₃ sulfurization in ammonium rhodanide vapor and identified the sequence of steps in lanthanum oxide conversion into oxysulfides and lanthanum sulfide using X-ray diffraction, IR absorption spectroscopy, and Raman spectroscopy. In the initial stage of the sulfurization process, we observed the formation of lanthanum dioxydisulfide, which converted into lanthanum dioxymonosulfide and lanthanum sesquisulfide during further sulfurization. Our results demonstrate that low structural perfection of lanthanum oxide allows reactive sulfur to penetrate the surface layer, which probably favors lanthanum dioxydisulfide formation.

The process of dehydration of Gd(OH)₃·nH₂O obtained by the sol-gel method from a solution of Gd(NO₃)₃, to Gd₂O₃ in the temperature range of 50–700°C was explored. The hydrogel and Gd₂O₃ structurization is shown to depend on the additives (AF-12 and 2-propanol). The final average particle size of Gd₂O₃ after annealing at 700°C is 20±2 nm, depending on the conditions of the synthesis. The resulting oxide particles are larger than the particles of yttrium oxide Y₂O₃ (17±2) obtained under the same conditions of the process due to the higher basicity of gadolinium and its higher coordination number with respect to the OH groups. This promotes the formation of crystalline phases of Gd(OH)₃ at lower temperature, 50–250°C, while maintaining a favorable structural short-range order in passing through an amorphous state to a crystalline Gd₂O₃.

The temperature dependences of the heat capacity ( C p) and the thermal conductivity (κ) in the temperature range from 300 to 773 K of polycrystalline gadolinium sulfide samples (γ-GdS y) with the...