Microemulsion Prepared Gd <sub> 2 </ Sub> O <sub> 3 </ Sub>: Tb ~ (3 +), Gd <sub> 2 </ Sub> O <sub> 2 </ Sub> S : Tb ~ (3 +) Nanoparticles And Luminescent Properties

The preparation, characterization and capability of nanosized Gd₂O₃:Tb³⁺ and Gd₂O₂S: Tb³⁺ were studied in the thesis. nanoparticles Gd₂O₃:Tb³⁺ and Gd₂O₂S:Tb³⁺ were prepared in the reverse microemulsions. With the nanoparticles obtained in this way, their crystal structure, shape and size were characterized. The mechanism of thermal decomposition of precursor nanosized oxalate and the kinetic parameters of thermal decomposition reaction-activation energy E and reaction order n were studied. And the photoluminescence of Gd₂O₃:Tb³⁺ and Gd₂O₂S:Tb³⁺, and the best luminescent ionic content of Tb³⁺ were measured.( 1 ) Gd₂O₃:Tb³⁺ luminescent nanoparticles were prepared in the reverse microemulsions based on triton X-100/n-hexyl alcohol, n-octane, and water. The particles has pure cubic structure proved by XRD, and has shown good dispersion and light agglomeration. With the water-to-surfactant molar(w=[H₂O]/[surfactant]) decreased, the nanoparticles' diameter are reduced from 20³0nm to 8¹5nm. Compared with the products which prepared by oxalate precipitation, the nanoparticles' size is small and the crystal forming temperature is decreased. The emission spectra of Gd₂O₃:Tb³⁺ include four characteristic peak which are located in 485, 543, 586 and 621nm. These emission peaks show the transition from ⁵D₄ to ⁷F₆, ⁷F₅, ⁷F₄ and ⁷F₃ of Tb³⁺ respectively. And the major emission peak is 543nm. The intensity of the peaks in the emission spectra are connected with the particles size of the powders. With the increase of nanoparticles' diameter, the intensity are enhanced. And the best luminescent ionic content of Tb³⁺ is 1 × 10^-3 mol/mol.(2) Proved by TG-DTA , XRD and FT-IR analyse of nanosized oxalate, the mechanism of thermal decomposition of precursor nanosized oxalate prepared by microemulsions are: Gd₂(C₂O₄)₃.10H₂O â†' Gd₂(C₂O₄)₃ + 10H₂O, Gd₂(C₂O₄)₃ â†' Gd₂O₂(CO₃) + 3CO+2CO₂, Gd₂O₂(CO₃) â†' Gd₂O₃ + CO₂. Which are complicated than bulk materials. The kinetic parameters of thermal decompositionreaction-activation energy E of stage 2 and 3 are 194.6 kJ.mor1, 110.9 kJ.mol"1 by using Ozawa method. And the reaction order n are 3.0 and 0.43, respectively, according to the TG curves.( 3 ) Nanosized Gd2O2S:Tb3+ can be prepared by the calcinations of nanoparticles Gd2O3:Tb3\ Na2CO3 and S in 1200°C. According to the PDF, the products has pure hexagonal structure. TEM photo show the nanoparitcles are sphere, having uniform diameter size of 10²0nm. And Because of high temperature calcinations, the nanoparticles conglomerate to form micron balls, whose diameter size are 0.2-0.5um. Compared with the microemulsion, the products prepared by oxalate deposition are anomaly micron flake. In addition, the emission spectra of nanosized Gd2O2S:Tb + are different to the micron materials. The intensity of the major emission peaks is enhanced obviously. And blue-shift are happened in the transition from 5D4 to 7F6.