High-Temperature Discharges in Ferroelectric Ceramics

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Abstract
Ceramic disks of barium titanate and lead zirconate titanate, when heated above 100°C, exhibit current discharges which cannot be attributed to the ferroelectric polarization of the material. These discharges are largest in the temperature interval 300°–600°C and depend primarily on the electrode material and its method of application. Discharges of several millicoulombs at voltages up to one‐half volt have been obtained from a ceramic disk one‐half inch in diameter and 30 mils thick having a silver electrode and an indium counterelectrode. Although thermoelectric, pyroelectric, and electret effects are observed in these samples, these phenomena contribute only a very small portion of the total discharge. At constant temperature near 350°C the discharge decays with time as the sum of two exponentials, falling to half‐maximum in periods of the order of one‐half hour. At higher temperatures the decay rate increases, while temperature cycling produces a voltage cycling superimposed on the decay. These findings support an explanation of the effect in terms of solid state chemical activity between the metallic electrodes and the titanate lattice.

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