Preparation of Diopside Fine Powders by Spray Pyrolysis and Its Sinterability

Abstract

Fine powders of diopside, CaMgSi2O6, were prepared by the spray pyrolysis method. Ca(NO3)24H2O, Mg(NO3)26H2O and Si (OC2H5)4 were dissolved into ethanol and refluxed under various time-temperature conditions before pyrolysis. Refluxing at 70°C for 1 day was necessary to prepare homogeneously mixed diopside precursor powders. Spray pyrolysis was made between 800° and 1000°C under the following conditions: volume of flowing solution, 2 to 15ml/min, volume of flowing air, 2 to 15l/min, and concentration of solution, 0.05 to 0.33mol/l. Almost all powder particles were hollow spheres of a few micron meter, which were composed of fine primary particles of submicron or less. These powders were calcined at 1000°C and sintered at 1275° to 1350°C after ground with a vibration mill. Relative densities up to 97.4% were achieved by firing at 1300°C for 1h without additives. This specimen showed dielectric losses much lower than those sintered with additives reported before.