Development of rare-earth ion-doped oxide phosphors upon band gap excitation and elucidation of their emission mechanism

(1)利用柠檬酸金属配合物或常规固相反应，采用pechinii型可聚合配合物法制备了Sr_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n= 1,2,∞)和Ca_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=2)钙钛矿相关ruddlesden - popper型化合物Sr_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n= 1,2,∞)和Ca_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=2)，并研究了它们的光致发光性能。这些化合物显示出与Pr^<3+>的f-f跃迁相对应的明显的发射。激发过程与基体中价带和导带之间的跃迁过程一致。Ca_3Ti_2O_7:Pr^<3+>表现出比Sr_3Ti_2O_7:Pr^<3+>强十倍以上的红光。这些化合物发光性质的差异源于寄主到激活剂的能量传递对结构的依赖，以及Pr^<3+>的位置对称性。在钙钛矿型钛酸盐R_<1/2>Na_<1/2>中合成了更多ap激发的TiO_3:Pr (R=La, Gd, Lu， Y)Pr^<3+>掺杂的钙钛矿R_<1/2>Na_<1/2>TiO3:Pr (R=La, Gd, Lu， Y)，研究了它们的结构、光学吸收和发光性能，并讨论了结构与光学性能之间的关系。R_<1/2>Na_<1/2>TiO3的光学带隙按R=La、Gd、Y、Lu的顺序增大，其主要原因是带宽度减小，同时Ti-O-Ti键角减小。在带隙光激发（UV）下，所有化合物都观察到Pr^<3+>从激发态^1D_2到基态^3H_4的f-f跃迁引起的强红色发射。发射峰波长按R=La、Gd、Y、Lu的顺序发生红移，这是由于Pr^<3+>晶体场分裂增加所致。结果表明，R_<1/2>Na_<1/2>TiO_3:Pr中的发光性质受R_< 3+>的4f^2基态和激发态之间的相对能级以及导价带的支配，其主要取决于结构，如：TiO6八面体的倾斜度、Pr- ti原子间距离和Pr离子的位置对称性。(3)掺Pr钙钛矿型锂离子导电氧化物A_0.6Li_0.3Ti_0.5Ta_0.5O_3: Pr （A=Ca, Sr）中Pr的占据位置和发光性能研究了掺Pr钙钛矿型锂离子导体A_<0.6-3x/2>Pr_xLi_0.3Ti_0.5Ta_0.5O_3 （A=Ca, Sr, 0≦x≦0.05）的晶格参数和发光性能。Ca_<0.6>Li_0.3Ti_0.5Ta_0.5O_3:Pr在紫外光激发下显示出对应于Pr^<3+> （^1D_2→^3H_4）的f-f跃迁的强红色发射，其能量对应于宿主带隙。而Sr_<0.6>Ti_<0.5>Ta_0.5O_3:Pr在蓝光激发下呈现蓝绿色和红色发射，对应于Pr^<3+> （^3H_4→^3P_4）的f-f跃迁。结果表明，这些发光性能的差异主要是由钙钛矿型氧化物中Pr的占据位置引起的。少

(1) Photoluminescence of Pr^3+-doped Ruddlesden-Popper-type titanates, Sr_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=1, 2, ∞) and Ca_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=2)Perovskite-related Ruddlesden-Popper-type compounds, Sr_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=1, 2, ∞) and Ca_<n+1>Ti_nO_<3n+1>:Pr^<3+> (n=2) were prepared by a Pechini-type polymerizable complex method using a citric metal complex or conventional solid state reaction, and their photoluminescence properties were investigated. The compounds show distinct emission corresponding to the f-f transitions of Pr^<3+>. The excitation process is consistent with the transition between the valence band and the conduction band in host materials. Ca_3Ti_2O_7:Pr^<3+> exhibits red emission more than ten times stronger than Sr_3Ti_2O_7:Pr^<3+>. The differences in luminescent properties among the compounds originate from the structure dependence of the energy transfer from host to activator Pr^<3+>, and the site symmetry of Pr^<3+>.(2) Photoluminescence upon band g … More ap excitation in perovskite-type titanates R_<1/2>Na_<l/2>TiO_3:Pr (R=La, Gd, Lu, and Y)Pr^<3+>-doped perovskites R_<1/2>Na_<1/2>TiO3:Pr (R=La, Gd, Lu, and Y) were synthesized, and their structures, optical absorption and luminescent properties were investigated, and the relationship between structures and optical properties was discussed. Optical band gap of R_<1/2>Na_<1/2>TiO3 increases in the order R=La, Gd, Y, and Lu, which is primarily due to a decrease in band width accompanied by a decrease in Ti-O-Ti bond angle. Intense red emission assigned to f-f transition of Pr^<3+> from the excited ^1D_2 level to the ground ^3H_4 state upon the band gap photo-excitaion (UV) was observed for all compounds. The wavelength of emission peaks was red-shifted in the order R=La, Gd, Y, and Lu, which originates from the increase in crystal field splitting of Pr^<3+>. This is attributed to the decrease in inter-atomic distances of Pr-O together with the inter-atomic distances (R, Na)-O, i.e., increase in covalency between Pr and O. The results indicate that the luminescent properties in R_<1/2>Na_<1/2>TiO_3:Pr are governed by the relative energy level between the ground and excited state of 4f^2 for Pr^<3+>, and the conduction and valence band, which is primarily dependent on the structure, e.g., the tilt of TiO6 octahedra and the Pr-Ti inter-atomic distance and the site symmetry of Pr ion.(3) Occupation site of Pr and luminescent properties in Pr-doped perovskite-type lithium ion-conducting oxides, A_0.6Li_0.3Ti_0.5Ta_0.5O_3 : Pr (A=Ca, Sr)We investigated the lattice parameters and luminescent properties of Pr-doped perovskite-type lithium ion conductors, A_<0.6-3x/2>Pr_xLi_0.3Ti_0.5Ta_0.5O_3 (A=Ca and Sr, 0≦x≦0.05). Ca_<0.6>Li_0.3Ti_0.5Ta_0.5O_3:Pr shows the intense red emission corresponding to the f-f transition of Pr^<3+> (^1D_2 → ^3H_4) on the ultraviolet photo-excitation with the energy corresponding to the band-gap of host. In contrast, Sr_<0.6>Ti_<0.5>Ta_0.5O_3:Pr exhibites blue-green and red emission on the excitation with blue light corresponding to the f-f transition of Pr^<3+> (^3H_4 →^3P_4) . It was found that these differences in luminescent properties primarily originate from the occupation site of Pr in these perovskite-type oxides. Less