Performance of US electrodes-insulators tested in the USSR U-02. Phase III

The performance of La(Mg)CrO3 and La(Mg)CrO3. ZrO2-base electrodes, MgO and MgAl2O4 electrical insulators, and nickel-mesh compliant attachments (US-USSR test in U-02 Phase III) has been evaluated. The nickel mesh provided satisfactory electrical, thermal, and thermomechanical attachment. Major degradation of cathodes is attributed to enhanced electrochemical reaction of K2CO3 midway between surface and attachment and ultimate hydration of reaction products. Extensive plasma surface reactions with Al2O3, introduced into channel by plasma from upstream components, caused extensive reaction with electrodes and insulators, surface flow, and bridging between electrodes. Chromium loss occurred near electrode surface due to thermal instability of LaCrO3. The monolithic MgO and MgAl2O4 insulators fractured with seed penetration through the cracks. Loss of electrical isolation between electrodes attributed to this seed penetration and electrode surface bridging