A CRITICAL-EXAMINATION OF A CRYOCHEMICAL METHOD FOR THE PREPARATION OF HIGH SURFACE-AREA SEMICONDUCTING POWDERS .3. FACTORS WHICH DETERMINE SURFACE-AREA

The effect of the nature of precursor salts on the surface area of mixed metal chlorides and mixed metal oxides prepared by freeze-drying was studied in the following systems: MgCl//2 multiplied by (times) 6H//2O-KCl, acetates and nitrates of lanthanum, strontium and cobalt, nitrates of nickel and cobalt. The intermediates as well as the final products were studied by electron microscopy. X-ray powder diffraction, thermogravimetric analysis and differential scanning calorimetry. Dehydration of MgCl//2 multiplied by (times) 6H//2O-KCl occurred with an increase in surface area, but any further effects due to the formation of the perovskite phase were not seen because of sintering.