Papers by Author: Hiroyuki Shimizu

Abstract: The Relationship between the Piezoelectric Properties and Crystal Lattice Deformation and Distortion Resulting from the Li Substitution in Li_XNa_0.52K_0.48-XNbO₃, Alkaline Niobate-Based Perovskite Ceramics of (Li, Na, K)NbO₃, Was Investigated. the Lattice Parameters of the Sample with a Li Content X = 0.05 and Having a Monoclinic System with Space Group PM Were a = 3.9789(6) Å, B = 3.9385(5) Å, C = 4.0134(6) Å, and B = 90.305(4)º. the E^T33/e0, Kr, and -D31 Values of the Sample by Poling in the Monoclinic System Were 450, 44.6%, and 57 PC/N, Respectively. on the other Hand, the E^T33/e0, Kr, and -D31 Values of the Sample by Poling in the Tetragonal System Were 600, 38.7%, and 56 PC/N, Respectively. the Remarkable Piezoelectric Properties of these Ceramics Can Be Attributed only to the Low Symmetry of their Monoclinic System, which Is a Subgroup of aMm2 and P4mm. Li_0.05Na_0.52K_0.43NbO₃ Ceramics with a Monoclinic System Were Observed to Have the Unique Piezoelectric Characteristics.

Abstract: Recently, we have developed crystal-oriented sheet forming (COSF) process from green sheet process and high-magnetic-field method. We formed c-axis-oriented (Sr,Ca)2NaNb5O15 (SCNN) sheets by the COSF process, and succeeded in realizing c-axis-oriented single-plate type piezoelectric ceramics (O-SP) and c-axis-oriented multilayered type piezoelectric ceramics (O-MLPC) for SCNN. From the measurement results of displacement induced by electric field, it was clarified that effective d33 of the O-SP was 210~240 pm/V. This value was about 3 times larger than that of the randomly oriented single-plate type, which was 70% of that of single crystal. Moreover, it was confirmed that O-MLPC indicated displacements 2.5 times as large as that of the conventional multilayer piezoelectric ceramics. In this study, we clarified that piezoelectric properties in bulk and multilayer structure can be drastically enhanced using the COSF process.