Effect of La doping on microstructure and ferroelectric properties of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films prepared by sol-gel method

The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.     

Li_6SrLa_2Nb_2O_(12):Pr~(3+)的发光性质

用高温固相法制备了Li6SrLa2Nb2O12:Pr3+,并通过X射线衍射仪及荧光光谱仪分析了其结构和发光性质.结果表明:激发光谱出现NbO7-6吸收和Pr3+的4f→4f5d激发跃迁;发射光谱出现强的绿光发射,其峰值位于491nm,同时在610nm处有弱的红光发射,这两种发射分别属于Pr3+的3P0→3 H4和1 D2→3 H4的电荷跃迁.Pr3+在Li6SrLa2Nb2O12:Pr3+中的最佳掺杂浓度为0.5mol%.     

不同络合剂对溶胶-凝胶法制备Bi_4Ti_3O_(12)粉体性能的影响

以Bi(NO3)3·5H2O和(C4H9O)4Ti为原料,分别以柠檬酸、乙酸、EDTA为络合剂,采用溶胶-凝胶法制备了Bi4Ti3O12,探讨了不同络合剂对所得粉体组成和光催化性能的影响.结果表明,以柠檬酸为络合剂时,600℃煅烧即可得到均匀分布的纯相Bi4Ti3O12粉末;以乙酸为络合剂时,800℃煅烧才可得到纯相Bi4Ti3O12.但是在600℃煅烧温度下,以乙酸为络合剂的产物的光催化性能最强,经紫外光照射120 min,对罗丹明B降解率达到了84%.     

纳米Na0.5Bi0.5TiO3粉体的水热合成研究

以Bi(NO3)3·5H2O、Ti(OC4H9)4为原料,研究和分析了水热条件下Na0.5Bi0.5TiO3(BNT)晶体生长和形成的影响因素.结果表明,在反应温度为160～180℃,保温时间为4～16h,NaOH浓度为4～12mol/L的条件下可制备出高纯度的纳米Na0.5Bi0.5TiO3粉体,其颗粒尺寸约为15～60nm.     

Yb3+/Pr3+共掺TeO2-ZnO-Na2O玻璃的能量传递和上转换发光

制备了Yb3+/Pr3+共掺TeO2-ZnO-Na2O玻璃.研究了980 nm泵浦下上转换发光光谱,分析了上转换发光机制.基于吸收光谱对Pr3+在TZN玻璃进行了Judd-Ofelt分析,计算了荧光跃迁几率,激发态辐射寿命,和荧光分之比.在450-750 nm范围内有多处上转换荧光,依次为479 nm(3P0→3H4),542 nm(3P0→3H5),589 nm(1D2→3H4),621 nm(3P0→3H6),651 nm(3P0→3F2)和687 nm(1D2→3H5).其中651 nm(3P0→3F2)红光明显强于其它以Pr3+ 3P0为初始能级的上转换光(479 nm,542 nm,621 nm).通过Dexter理论,计算得到了碲酸盐玻璃中Yb3+→Pr3+共振能量转移参数为CD-A=2.67×10-40 cm6/s, 转移效率为16.5%.     

Pr~(4+)离子并入BaTiO_3的Ti位的探索

为了开发Pr4+在BaTiO3陶瓷Ti位的EPR样品,采用冷压陶瓷技术制备Pr掺杂和La/Pr共掺杂BaTiO3陶瓷.研究表明:即使在Ti位占据的Pr4+设计下,增加Pr含量也不能迫使Pr离子进入Ti位,并产生第二相.对于名义分子式为(Ba1-xLax)(Ti1-y-x/4Pry)O3(BLTP)的陶瓷,借助La3+在Ba位的并入,也很难将Pr离子以Pr4+形式挤压到BaTiO3陶瓷的Ti位,但可形成低Pr掺杂的单相陶瓷.     

Bi_(3.25)La_(0.75)Ti_3O_(12)纳米材料的水热合成研究

以分析纯硝酸铋、硝酸镧、钛酸四丁酯为原料,采用水热法制备了Bi3.25La0.75Ti3O12(BLT)纳米材料。用XRD和SEM对样品的物相和形貌进行了表征。讨论了矿化剂(NaOH)浓度和水热反应时间对BLT物相的影响。表明合成产物为正交相钙钛矿结构Bi3.25La0.75Ti3O12纳米片,厚度约10 nm,平均边缘尺寸约100 nm。当反应温度为200℃时,反应时间在12 h到48 h,矿化剂浓度在1 mol/L到2 mol/L范围内能有效合成Bi3.25La0.75Ti3O12。     

GdAl3(BO3)4:Eu3+红色荧光粉的结构和荧光特性

用溶胶凝胶法合成GdAl3(BO3)4:Eu3 红色荧光粉.晶化温度为960℃,晶化时间为2 h;用X射线衍射进行结构表征,并用Jade5程序对GdAl3(BO3)4:Eu3 粉末样品的X射线衍射数据进行了指标化.结果表明:GdAl3(BO3)4:Eu3 为六方晶系,晶胞参数a=9.299 2 nm,c=7.257 7 nm;荧光性能测试结果为:室温613 nm监测,其激发光谱峰为:270,391,400,472,542,728,766和791nm.在270 nm激发下,最大发射峰为613 nm.     

Dynamic dam-reservoir interaction analysis including effect of reservoir boundary absorption

The Bi3.25La0.75Ti3O12 thin films were fabricated on the Pt/Ti/SiO2/Si substrates using sol-gel method. The structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The thin films showed a perov- skite phase and dense microstructure. The 2Pr and 2Vc of the Bi3.25La0.75Ti3O12 thin films annealed at 700℃ were 18.6 μC/cm2 and 4.1 V, respectively, under an applied voltage 10 V. After the switching of 1×1010 cycles, the Pr value decreased to 90% of its pre-fatigue values. The films showed good insulating behavior according to the test of leakage current. The dielectric constant and the dissipation factor of the Bi3.25La0.75Ti3O12 thin films were about 176 and 0.046 at 1 kHz, respectively.     

Ferroelectric properties of Bi_(3.25)La_(0.75)Ti_(3)O_(12) thin films prepared by sol-gel method

The Bi3.25La0.75Ti3O12 thin films were fabricated on the Pt/Ti/SiO2/Si substrates using sol-gel method. The structure and morphology of the films were characterized us-ing X-ray diffraction and atomic force microscopy. The thin films showed a perov- skite phase and dense microstructure. The 2Pr and 2Vc of the Bi3.25La0.75Ti3O12 thin films annealed at 700℃ were 18.6 μC/cm2 and 4.1 V, respectively, under an applied voltage 10 V. After the switching of 1×1010 cycles, the Pr value decreased to 90% of its pre-fatigue values. The films showed good insulating behavior according to the test of leakage current. The dielectric constant and the dissipation factor of the Bi3.25La0.75Ti3O12 thin films were about 176 and 0.046 at 1 kHz, respectively.