Effect of the La<sup>3+</sup>-Doping Concentration on the Properties of TiO<sub>2</sub> Thin Films by Sol-Gel Process

Abstract

Various rare earth (La3+) doped titaniumdioxide(TiO2) thin films (La3+-doped TiO2) have been successfully prepared on a glass substrate by a sol–gel dip coating route using titanium tetraisopropoxide and lanthanum chloride as the initial materials. After the La3+-doped TiO2 thin films were calcined at 500°C for 1h, the effect of La3+-doping on the properties of films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric- differential scanning calorimeter techniques (TG/DTG). The XRD results showed that all La3+-doped TiO2 thin films contained only a single crystalline phase of anatase TiO2 after calcining at 500°C for 1h. Moreover, the XRD results also revealed that the crystallinity and crystalline size decreased with increased La3+-doping. SEM micrographs showed that all La3+- doped TiO2 thin films have smooth surfaces containing granular nanocrystallines and are without cracks. TG/DTG measurement showed that there was a significant weight loss of the TiO2 precursor calcined in the temperature range from ambient to 660 °C, which was due to the volatilizing of water and organic and the phase transformation.