Reaction and diffusion between PLZT ceramics and Ag electrode

Volume and grain boundary diffusions of silver as an electrode material in PLZT were studied by means of a secondary ion mass spectrometry (SIMS). The volume diffusion coefficients (D-v) are described by an Arrhenius law as follows: D-v=0.12 exp{-(258+/-25) (kJ.mol(-1))/RT} (cm(2).s(-1)). Distribution of silver ions in PLZT ceramics was observed by imaging of SIMS, and indicated that grain boundaries act as the high diffusivity path for silver element in PLZT. The temperature dependence of grain boundary diffusion coefficients (D-gb was formulated as follows: D-gb=43.50 exp{-(236+/-46) (kJ.mol(-1))/RT} (cm(2).s(-1)). The intergranular fracture is considered to be associated with the grain boundary diffusion of silver. At higher temperature, a reaction layer was remarkable near the interface between PLZT and electrode. Silver electrode reacted with PLZT, and then the reaction layer formed, as follows: PLZT+Ag-->PLT+ZrO2+(PbO+Ag) (PLT: (Pb, La)TiO3). It is clear that the grain boundary diffusion of silver strongly effects to the mechanical and chemical strength and plays an important role in the reaction between Ag electrode and PLZT ceramics.