The effects of dopants, e.g. oxides of La, Sb, Nd, Gd, Y, Nb etc have been studied on the PTC behaviour of polycrystalline BaTiO3. Sb-doped material showed the best characteristics under our experimental conditions. A systematic study on the effects of different electrode materials like Ag, In, In-Ga and Ni has also been carried out. The contact resistance was exceptionally high for Ag and In, but negligible in case of either In-Ga or Ni. Impedance measurement at different frequencies has been used to distinguish between the intra-grain, inter-grain and electrode-contact resistances. Power-limiting capability of the prepared specimens has been tested by measuring I-V characteristics.
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Basu et al. (1986) studied this question.
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