The Preparation And Properties Exploration Of ReeTi₂Al₉O₁₉ Rare-earth Complex Oxide

ReeTi₂Al₉O₁₉ (Ree = La, Ce, Nd, Eu, Pr, etc.) is a group of crystal cell huge rare earth oxides. Because of complex Crystal structure it is difficult to form a single phase. Therefore, the application performance study has been seldom reported. Based on the existing research in preparation and crystal structure, this paper mainly research in the comprehensive physical properties and luminescence performance through improving preparation process.The pure phase of ReeTi₂Al₉O₁₉ (Ree = La, Ce, Nd, Eu, Pr) composite oxide was synthesized by high temperature solid state and nitrate pyrogenation respectively. Notably, the novel compounds (NdTi₂Al₉O₁₉, EuTi₂Al₉O₁₉, PrTi₂Al₉O₁₉) firstly were obtained. The XRD shows that all powder samples are single phase and the diffraction peaks match well with the standard PDF:37-1233. The SEM confirms that the crstal morphology is rule, but grain size is not uniform by high temperature solid. However, the feature of the specimen obtained by nitrate pyrogenation is that crystal integrity, grain size uniformity, about 2³Î¼m, and bonding between the grains more closely.Ceramic samples were pressureless sintering at 1500℃for 4h with LaTi₂Al₉O₁₉ as the raw material after molding under pressure 100Mpa. The phase and morphology of the samples were characterized .The physical properties consist of bulk density, apparent porosity, linear shrinkage, thermal conductivity also were analyzed. The result declares that the ceramic specimens are pure phase, crystallization is better. The linear shrinkage rate is so low as 9.03% , apparent porosity is below as 1.55%, bulk density is 4.31g/cm³, relative density is more than 98%. 302K, the average thermal conductivity is 2.02 W/K·m. LaTi₂Al₉O₁₉ is a novel thermal barrier material, as it is no high temperature phase transition, low thermal conductivity and has superior heat temperature stability.The model of LaTi₂Al₉O₁₉ was constructed and calculated by CASTEP module based on density functional theory (DFT) plane-wave pseudopotential method. It has high electric insulativity by predicted. The resistivity measured is 8.1323×10⁸Ωm, namely,experimental result consistents with the theoretical prediction.A phosphor of LaTi₂Al₉O₁₉:Sm³⁺ was synthetized with nitrate pyrogenation method, The article tests the phase and morphology, and mainly investigates of the luminescence property. The XRD indicates that the single phase of LaTi₂Al₉O₁₉:Sm³⁺ which well crystallized was prepared, that is to say, to dope with trace of Sm³⁺ does not change the crystal structure of host material. The SEM demonstrates that the grain morphology is rule, uniform size is about 1²Î¼m. The emission spectra states that the sample possesses the feature emission peak of Sm³⁺, peaks type are narrow and sharp, thereinto, 597nm is the strongest, corresponding to 4^G_5/2→6^H_7/2 energy level transition. To 597nm as the monitoring wavelength, the excitation spectra was obtained, in which 402nm is the strongest peak, duing to 6^H_5/2→4^F_7/2, and the effective excitation wavelength of Sm³⁺ is coverage of the near UV, blue, blue-green band. The result also proves that the optimum doping molar ratio is 3% amount. The concentration of Sm³⁺ which is located on asymmetric point is greater than those symmetric one.