Development of silver–metal oxide reactive air braze alloys for electroding PZT ceramics

Existing multi-layer devices using leadbased piezoelectric ceramics utilize an internal electrode that does not bond the ceramic layers. Improvements in device performance and processing could be gained if the electrode also acted as a bond between the ceramic layers. In the current work, the feasibility of brazing lead zirconate titanate (PZT) in ambient conditions utilizing silver-based alloys containing low melting temperature metal oxides was investigated. Wettability, joint fracture strength, and microstructural analyses were conducted for various PZT/silver–metal oxide systems. The metal oxide additions included copper (II) oxide, vanadium pentoxide, lead (II) oxide, and eutectic lead oxide-titanium (IV) oxide. The silver–copper oxide (Ag–CuO) system demonstrated the most potential; exhibiting an apparent contact angle of approximately 64 and an average braze joint fracture strength that was approximately 62% of the monolithic PZT strength. In addition, no significant reaction product formation was observed at the silver/ PZT interface. However, a preliminary investigation of multi-layer devices electroded with Ag–CuO alloys indicated a decrease in the resistivity of the brazed PZT by several orders of magnitude.