La3+掺杂TiO2纳米粉体的相组成和光催化性能

Phase composition and photocatalytic properties of La3+-doped TiO2 nanopowders

摘要:

本文采用溶胶-凝胶法制备了La3+掺杂TiO2。利用XRD、TEM、HRTEM、STEM-EDS、XPS和Uv-vis对样品进行表征，讨论La3+掺杂TiO2在相变过程中的物相组成、平均晶粒尺寸、微观结构、化学态和紫外-可见吸收光谱等方面的变化。掺杂La3+明显地抑制了TiO2的相转变和晶粒长大，有效地改善了TiO2的分散性，并减小了TiO2的平均颗粒尺寸。随着煅烧温度升高，La3+掺杂TiO2逐渐析出第二相La4Ti19O24，其会与TiO2板钛矿相形成非共格界面，并以不规则球体的形式在TiO2基体表面析出的。第二相La4Ti19O24来源于点缺陷在La掺杂TiO2晶界的偏析，偏析驱动力主要是是弹性应变能。随着煅烧温度的升高，La3+掺杂TiO2中O1S的原子百分比逐渐降低，La3d的原子百分比逐渐升高，且La3d主峰的高结合能端有一个能量损失峰，煅烧后存在Ti3+；掺杂La3+使TiO2的光吸收带边红移，但随着煅烧温度的升高，其光吸收带边蓝移。

Abstract:

Sol-gel method was used to prepare La3+-doped TiO2 Nanopowders. The sample was characterized with XRD, TEM, HRTEM, STEM-EDS, XPS and ultraviolet-visible (UV-Vis) spectroscopy. The changes of the La3+-doped TiO2 in the phase transition were discussed on the aspects of its phase composition, the average grain size, the microstructure, the chemical states and UV-Vis absorption spectroscopy. Doping with La3+ significantly suppressed the phase change and grain growth of TiO2. It effectively improved the TiO2 dispersibility and reduced the average particle size of TiO2. With the increase of the calcination temperature, the second phase La4Ti19O24 gradually precipitated from the La3+-doped TiO2 and formed an incoherent interface with the Brookite TiO2 phase, which precipitated in the form of irregular spheres from the surface of the TiO2 base. Secondary phases are originated from segregation of point defects at grain boundaries in La3+ doped TiO2. The segregation driving force is mainly the elastic strain energy. With the increase of calcining temperature, the atomic percentage of the O1S in the La3+-doped TiO2 gradually decreased, and that of the La3d gradually increased. There was an energy loss peak at the higher binding-energy side of the main peak of the La3d, and Ti3+ existed after the calcination. La3+ Doping makes the optical absorption bandedge of the TiO2 red-shifted. But with increasing calcination temperature, the optical absorption bandedge was blue shifted.