Pure and La3+ / Nd3+ Doped SrTiO_3 Powders Obtained by Solid State Reaction and Microwave Assisted Hydrothermal Synthesis

摘要

Strontium titanate ceramic powders (SrTiO_3), pure and doped with lanthanum (La~(3+)) and neodymium (Nd~(3+)), were synthesized by solid state reaction (SSR) and microwave assisted hydrothermal technique (MHT). For SSR, a mixture of SrCO_3, TiO_2, La_2O_3 and Nd_2O_3 oxides was performed in stoichiometric ratio, to produce SrTiO_3 (STO), Sr_(0.96)La_(0.04)TiO_3 (STO-04La), Sr_(0.96)Nd_(0.04)TiO_3 (STO - 04Nd) and Sr_(0.96)La_(0.02)Nd_(0.02)TiO_3 (STO-02La02Nd), in a ball mill, for 3.5 h. This mixture was dried at 70℃ for 24h. This powder was calcined at 1150℃ for 2h in a conventional oven. For MHT synthesis, Ti(C_4H_9O)_4, SrCO_3, La_2O_3 and Nd_2O_3 precursors were solubilized in nitric acid (10M), in stoichiometric proportions to form STO , STO-04La, STO-04Nd and STO-02La02Nd. This solution was precipitated adding NH_4OH (10M). Quota of 2g of precipitated powder was then dried in an air oven at 70℃ for 24 hours, and then added to 40 ml of a KOH solution (10M). These suspensions were subjected to MHT for lh, at 120℃. The ceramic powders obtained by the two routes were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystallite size was calculated by Scherrer method and from SEM image, linear intercept method for both the SSR and MHT powders was used to measure the particles size, which show the increase of particles size related to the cation substitution.