Piezoelectric properties of CuO-added (Na0.5K0.5)NbO3 ceramic multilayers

Multilayered ceramics (MLCs) laminated with 20 layers of CuO-added (Na0.5K0.5)NbO3 (CNKN) tape were well sintered at 960 °C with an average grain size of 5.0 μm. They exhibited good piezoelectric properties of ε33T/ε0=709, d33 = 114 pC/N, kp = 0.34 and Qm = 793. The 80Ag/20Pd electrodes were well formed on the CNKN MLCs when they were co-fired at 960 °C for 2 h. A piezoelectric speaker fabricated using 6-layer CNKN MLCs exhibited an average sound pressure level (SPL) of 75 dB in the range between 300 and 20,000 Hz with a maximum SPL of 90 dB. This value is comparable with that of a loud stereo radio, indicating that the CNKN MLC is a good candidate material for piezoelectric speakers.