Reliability of Nickel Inner Electrode Lead-Free Multilayer Piezoelectric Ceramics

Abstract

The environmental reliability of lead-free (K,Na)NbO 3 -based multilayer ceramics with nickel inner electrodes was studied. The multilayer specimen with good piezoelectric properties was successfully obtained by adding excess zirconium to a (K,Na)NbO 3 -based composition. Excess zirconium probably accelerated the solid solution of potassium into the crystal lattice and prevented potassium evaporation. The electric resistivity and piezoelectric properties of the ceramics were extremely stable at a high temperature (85 °C), a low temperature (-40 °C), and a high humidity [85 °C/85% relative humidity (RH)]. Their change rates were below 10% in 500 h studies. The stability was also high in the thermal shock (from -40 to 85 °C) test. It is thus concluded that the (K,Na)NbO 3 -based composition containing excess zirconium is a good candidate material for nickel electrode multilayer ceramics.