Interaction between lead iron niobate/tungstate ceramics and silver/palladium metals

The interactions between ferroelectric Pb(Fe1/2Nb1/2)O-3 (PFN)/Pb(Fe2/3W1/3)O-3 (PFW) perovskite ceramics and silver/palladium metals were systematically investigated through the phase formation and microstructural variation. Silver did not react with PFN/PFW ceramics after heating to 900 degrees C, and perovskite grains were only distributed among the matrix of silver. After being heated with 70Ag/30Pd at 900 degrees C, no perovskite phases were significantly altered; however, in the PFN-rich ceramics, the palladium content in the alloy decreased along with the formation of PdO. Pure palladium was found to have the highest reactivity with PFN/PFW ceramics. The reactions between palladium and ceramics occurred vigorously from 850 degrees C and resulted in markedly different microstructures. Palladium caused PFW to decompose into PbWO4 and Pb2WO5, and also led to the dissociation of PFN/PFW ceramics to produce pyrochlore phases and Fe2O3. The reactivity of palladium with perovskite phases was positively correlated with the PFN content in specimens. In addition, increasing the PFN content also tended to postpone the reduction process of PdO to palladium. (C) 1997 Elsevier Science Limited and Techna S.r.l.