As a candidate for lead-free piezoelectric materials, Li 2 O excess 0.95(Na 0.5 K 0.5 )NbO 3 -0.05LiTaO 3 (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding Li 2 O as a sintering aid. Abnormal grain growth in NKN-5LT ceramics was observed with varying Li 2 O content. In the 1 mol% Li 2 O excess NKN-5LT samples sintered at 1000°C for 4 h in air, electromechanical coupling factor and piezoelectric constant of NKN-5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. Lead-free piezoelectric ceramic, Li 2 O excess NKN-5LT, multilayer ceramic actuators (MLCA) were fabricated. 10×10×1 mm 3 size MLCAs were fabricated by conventional tape casting method. The displacement of Li 2 O excess NKN-5LT MLCA with 3 mm thickness was~1 μm at 150 V.

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Dielectric and piezoelectric properties of grain oriented (Bi 0.5 Na 0.5 )TiO 3 -BaTiO 3 ceramics were investigated in a process that the templated grain growth and hot pressing methods were employed. A ceramic composition in Bi-based perovskite structure family, (Bi 0.5 Na 0.5 )TiO 3 -BaTiO 3 , was chosen as a matrix material and plate shaped SrTiO 3 as a template. To examine the combined process effect on piezoelectric properties, three processes, conventional solid reaction, templated grain growth and the combine treatment of templated grain growth and hot-pressing, were compared. Specimen processed by templated grain growth and hot pressing methods exhibited better piezoelectric coefficient, d 31 (−79.6 pC/N) and electromechanical coefficient, k 33 (0.35) than those of the other specimens, fabricated by solid reaction and templated grain growth, respectively. The improved properties were attributed to reduction of pore existing in matrix, which is related to abnormal grain growth from SrTiO 3 template and its resultant heterogeneous shrinkage.

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In this study, We investigated the possibility of use of multi-stack type piezoelectric devices. The dielectric and piezoelectric properties of the device were examined. To match the external vibration frequency with the device resonant frequency, the metal type manipulator was combined with the multi-stack device. Under an external force of 1 G at 120 Hz, the device exhibited a voltage of 12 V and a power of 60 mw in resonance mode.