Analysis on the aging characteristics of PTCR of donor-doped barium titanate

The resistance versus time curves of room temperature unload ageing, high temperature unload ageing and high temperature continuous load test ageing of PTC thermistors are measured. At the initial aging stage under both high temperature unload ageing and high temperature continuous load test ageing, the resistance decreases first, and then increases, which are different from that of the room temperature aging. Such abnormal phenomena exist in the initial ageing stage and are attributed to buffering of the unstable mechanical stress and desorption of the absorbed oxygen molecules under the thermal action. R–T characteristic curves of aged sample are different from that of oxidized and reduced samples. A new mechanism is proposed to interpret the aging characteristics of the donor-doped BaTiO3 PTC thermistor.