| 摘要 |
PROBLEM TO BE SOLVED: To heighten Curie point of a ceramic and to improve piezoelectric characteristics of the ceramic, especially Qmax without incorporating lead by constituting the ceramic, with a bismuth layered compound having SrBi4Ti4 O15 type crystal and specifying the axis ratio c/a of its crystal lattice. SOLUTION: A piezoelectric ceramic is constituted of a bismuth layered compound having SrBi4Ti4O15 type crystal, wherein the axis ratio of the crystal lattice is controlled so that a=b and the value of c/a is in the range of 7.49 to 7.67, preferably 7.49 to 7.54. This piezoelectric ceramic is produced by mixing powders of compounds, being starting materials, of oxides, or carbonates, hydroxides, oxalates or nitrates, each being converted into an oxide by firing, so that a prescribed composition is obtained, then granulating the mixture together with a binder such as PVA, press forming, then debinding the formed body, further sintering the resulting formed body at 1,150 to 1,300 deg.C and finally subjecting the sintered body to polarization treatment at about 150 to 300 deg.C. Thereby, a piezoelectric ceramic having high Curie point of >= about 450 deg.C and Qmax of >= about 20 can be obtained. |
