Positive temperature coefficient in Ho-doped BaTiO3 ceramics Original Research Article

A series of Ho-doped barium titanate ceramics were prepared with dopant concentrations of: 0.03, 0.15, 0.27, 0.4 and 2.0 at.% Ho. DC resistivity measurements were carried out as a function of temperature from 10 up to 350°C. The strong (exponential) anomalous increase of the resistivity at the Curie temperature, TC≈110°C, was discussed in terms of Heywang model of positive temperature coefficient (PTC) of resistance. The inclusion of Ho has no effect on the room temperature bulk characteristics, as the samples were conductive at room temperature. The lowest dopant concentration was found to give the steeper resistivity rise at the Curie temperature and is recommended for practical applications in thermistors.