EFFECT OF ATMOSPHERE ON THE WETTING OF BATIO3 BY ELECTRODE METALS

BaTiO3 ceramics (with a broad temperature dependence of permittivity) are examined for wetting properties in different atmospheres such as vacuum, Ar and N2. The contact angles were measured with photographs. Ag and Cu showed a contact angle of 90-degrees in a vacuum, and 130-degrees and 105-degrees in Ar, respectively. These metals bonded with the ceramics. However, Pb and Sn had contact angles of 150-degrees and 149-degrees in a vacuum and 138-degrees and 135-degrees in Ar, respectively. The contact angles are discussed with the surface tension of metal as well as the ratio of tension to oxidation potential of a metal. The smaller the ratio, the larger a contact angle is. It was predicted that the metals with smaller ratios, such as Pb and Sn, were easily oxidized by oxygen from BaTiO3 in vacuum, and the oxides are stable, leading to less surface tension. The cross sectional analysis revealed that neither Ag nor Cu diffused into the ceramics.