Wetting of ZnO-ceramic with alloys of the silver-tin system in vacuum

ZnO is interesting as a promising material for use in various industries; in these applications there it is a need for metallization of ZnO-based materials, as well as their joining. For these purposes the using of liquid metal fillers is effective. Despite this, there are only a few single works that investigate issues related to the wetting and adhesion of metallic melts on the surface of zinc oxide or materials based on it. Therefore, the wetting of zinc oxide was investigated by Ag—Sn melts. intered ceramics made of pure ZnO without additions with porosity of 15%, silver and tin high purity were studied. Silver-tin alloys were prepared by previous melting in a vacuum. The wetting experiments were performed by the sessile drop method in vacuum. Addition of tin to silver can very significantly improve the wetting of the ZnO melt; there is a clear concentration dependence. The smallest of the contact angle is 57°. For the con¬centration of tin 5% at., when wetting has not yet been reached, a transition layer is observed between ceramics and metal. It is noticeable that lines, both between the ZnO substrate and the transition layer, and between the transitional layer and the frozen drop, are very uneven. Therefore, it can be concluded that the transition layer was not appeared due to adsorption, but formed as a result of the interaction of Ag—5Sn with ZnO, in particular uneven dissolution of the components of the substrate, possibly with the formation of a non-stoichiometric zinc oxide. In the case of tin concentration 10% (at.), when the melt wet the substrate, there is a zone containing two phases, dark and light (metal) in the ceramics under the drop. This two-phase area is obviously formed as a result of the impregnation of the melt in the pores in ceramic.Therefore, increasing the concentration of tin in Ag—Sn melts significantly improves the wetting of ZnO-ceramic by these systems, but the formation of developed transitional layers, as well as intensive impregnation of the melt deep into the ceramics complicates the use of these alloys for brazing or metallization of materials based on ZnO. Keywords: zinc oxide, wetting with metals, contact interaction, microstructure, transition layer