Thermal diffusivity and electron transport properties of NTC samples obtained by the photoacoustic method

Thermal diffusivity and electron transport parameters of sintered NTC samples were determined by the photoacoustic (PA) technique. Powder mixtures composed of MnO, NiO, CoO and Fe2O3 were milled to nanometer particle size. NTC discs were dry powder pressed and sintered at different temperatures in the range from 900 °C to 1300 °C for 30 min. A second group of NTC discs was sintered at 1200 °C with the sintering time varying from 30 min to 360 min. These NTC samples were polished and exposed to a chopped laser beam in order to plot a response in the acoustic range. The thermal diffusivity of sintered NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic technique. An increase of thermal diffusivity with the sintering temperature and time of sintering was observed.