| The effects of dopants, e.g. oxides of La, Sb, Nd, Gd, Y, Nb etc
have been studied on the PTC behaviour of polycrystalline BaTi03 •
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 intragrain,
inter-grain and electrode-contact resistances. Power-limiting
capability of the prepared specimens has been tested by measuring
I-V characteristics. |
