Thermal transformations of lead oxides

Differential scanning calorimetry, differential thermogravimetry, X-ray analysis and electronic microscopic studies of thermal transformations of PbO2 were carried out. Formation of fine dispersed (less than 100 nm) particles of alpha-PbO was observed at PbO2 thermal decomposition at heating to 580 degrees C. Reverse reaction of Pb3O4 formation from PbO was found at cooling and annealing at 400 degrees C in air. At heating of alpha-PbO to 650 degrees C the particle growth to 1 mu m with formation of beta-PbO took place. Thermal decomposition with formation of beta-PbO particles with size from 0.3 to 1 mu m at PbO2 heating to 650 degrees C was observed. Transition from PbO to Pb3O4 at cooling of sample heated to 650 degrees C was not detected. Interpretation of observed phenomena from the point of view of particle size influences on the shift of alpha-PbO <->beta-PbO phase transition temperature and on the chemical activity of phases are presented.