Abstract
The effects of doping and firing atmosphere on the electrical resistivity of polycrystalline barium titanate were studied. For the firing in nitrogen flow, the resistivity fell down to 10 ohm-cm with 0.05 mole percent Dy2O3 addition and did not show any appreciable change for larger additions. The firing in oxygen flow brought about a resistivity minimum near 0.1 mole percent Dy2O3 addition. The grain growth was suppressed with the increase of Dy content and in oxygen flow. The small grain was easily oxidized to have a high resistivity, while the large grain subjected to surface oxidation showed a pronounced PTC effect. Additions of Mn-, Cu-, Bi- or Tl-oxide together with Dy2O3 served to increase the electric resistivity. The resistivity rise also depended on the firing atmosphere in the respectively characteristic ways.

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