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Contacting Methods for C12A7 Electride Ceramic

K. Waetzig, A. Rost, J. Schilm, M. Tajmar, A. Michaelis

Journal of Ceramic Science and Technology, Vol. 11, No. 1 (2020), pp. 11-16

DOI: 10.4416/JCST2019-00032

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Abstract

C12A7:e- ([Ca24Al28O64]4+4e-) ceramic is a material with high electrical conductivity and low work function, so that this ceramic is suitable as an electron-emitting material. Although the bulk material indicates these extraordinary properties, the surface of the ceramic is insulating. Therefore, a metallization film is needed to realize an electrical contact with low ohmic losses for the application of the material. In this study, we investigated three different metal pastes (Pt, Au and Cusil-ABA®) for contacting the surface and measured the reduction of the resistance during the firing process of the pastes. The resistance of the contacted C12A7:e- was determined as a function of the temperature under nitrogen atmosphere. Additionally, the oxidation behaviour of the electride was observed based on increasing resistance when the material was heated in air.The lowest resistance was measured with Ag-based braze (Cusil-ABA®), however, cracking of the contacted ceramic was observed. Alternatively, contacting with Au reached a specific resistance of 5.4 Ω cm (T = 800 °C).

Keywords

Electron emitter, conductive ceramic, C12A7, calcium aluminate, metallization, contacting

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