Effect of pH Value on Preparation of La_2CuO_4 Microcrystallites Synthesized by Sol-Gel Process

摘要

La_2CuO_4 crystallites were prepared via a sol-gel process using lanthanum nitrate and cupric nitrate as raw materials, distilled water as solvent, citric acid as complexing agent and ammonia to control the pH value. The as-prepared La_2CuO_4 crystallites were characterized by XRD, FESEM, TEM and UV-Vis spectra. Results show that the crystallization property of La_2CuO_4 crystallites increases firstly and then decreases with increasing of the solution pH value from 1.0 to 2.5, but all of the samples exhibit single sphere-like morphology. It is found that when the solution pH value is controlled at 2.0, the grains display uniform distribution and the size ranges from 100nm to 120nm after sintering at 600°C for 2 hours. The optical band gap of the as-prepared La_2CuO_4 crystallites was calculated to be 1.38eV.