Study of microscopic heat sources in semiconducting barium titanate ceramics

If high electric fields are applied to semiconducting barium titanate ceramics, the rapid temperature rise caused by power dissipation makes it difficult to separate the field dependence of the resistance from its temperature dependence. For that reason the microscopic temperature rise during a voltage pulse was calculated by a theoretical model for the heat production and the heat flow inside a single grain. In addition, the local temperature behavior was measured experimentally by means of an infrared radiometric microscope. The fast temperature rise during a voltage pulse (350 V/mm; 400 μs) and the cooling off immediately after the end of the pulse prove that there are significant heat sources at the grain boundaries. In ceramics with relatively large grains (30–60 μm) temperature differences up to 50 K within a single grain were measured.