CRYSTAL CHEMISTRY OF CERAMIC DIELECTRICS.

Gradual changes in experimental and commercial Ti02 and BaTi03 bodies upon application of DC-stresses at high temperatures were observed and measured during and after the test. The changes in resistivity are sometimes accompanied by changes in capacity, loss factor and color. The current producing these changes has the features of an absorption current: it can be partly recovered; the discharge current can be measured over very long periods of time. Investigation of the effect of the electrode material on all changes occurring reveals that only the electrode material at the anode has an influence on the sign and on the rate of the change. Humidity has a very detrimental effect upon some dielectrics. Treatment in a humid atmosphere at 1000C stores protons in some form in the material; these protons become activated during life test and produce rapid degradation. After removal from the DC life test, the changes produced by the DC stress disappear and the sample might recover completely, if the degradation damage has not been too severe. There are also chemical means to prevent the entering and migration of the two mobile defects. (Author)
Continuation of Contract DA-36-039-AMC-00107(E).