Preparetion of Ultra-fine Perovskite-type LaFe03 Powders by Sol-gel Method from Inorganic Salts

Abstract

erovskite-type LaFe03 powders were prepared by drop coprecipitation method. An aqueous solution of La(NO₃)₃ and Fe(NO₃)₃ was dropped slowly (0.4 ml⋅ min-1) into an water-ethanolammonia solution at 40°C. The resultant gel was calcined at temperatures down to 630 °C for 2 h. The sizes of LaFe03 polycrystals were found to be as low as 13-20 nm by XRD and TEM. Their BET surface areas were measured to be 20-49 m2- g-1. In consequence of the experiment with change of coprecipitation temperature, stirring speed, dropping speed or calcination conditions of temperatures and time, the most effective factor to determine the size of ultra-fine particle were found to be the calcination temperature. In addition, the maximum surface area was obtained by short calcination time and ultrasonic stirring as secondary effects. The minimum crystallite size of LaFeO₃ was obtained around the crystallization temperature (630 °C).