主权项 |
1. A piezoelectric drive element, comprising:
a composite ceramic that combines a first piezoelectric ceramic having spring characteristics such that its elastic constant decreases as a vibration speed increases, with a second piezoelectric ceramic having spring characteristics such that its elastic constant increases as a vibration speed increases; and external electrodes provided on side faces of the complex ceramics in a manner facing each other across the complex ceramics; wherein an AC electric field at and near a resonance frequency is applied to the external electrodes to drive the piezoelectric drive element, wherein the first piezoelectric ceramic is a PZT-based lead piezoelectric ceramic, BaTiO3, (Ba1/2Na1/2)TiO3, (Ba1/2K1/2)TiO3, {(K1-xNax)1-yLiy}(Nb1-z-wTazSbw)O3 (0≦x≦1, 0≦y≦0.2, 0≦z≦0.4, 0≦w≦0.2), or a solid solution ceramic containing at least two of the foregoing, while the second piezoelectric ceramic is Sr2-xCaxNaNb5O15 (0≦x≦2), Sr2NaNb5O15, Ca2NaNb5O15, Sr2KNb5O15, Ba2LiNb5O15, Ba2NaNb5O15, Ba2KNb5O15, K3Li2Nb5O15, Ba2Bi1/3Nb5O15, Pb2NaNb5O15, Pb2KNb5O15, or a solid solution ceramic of tungsten bronze type containing at least two of the foregoing, wherein a volume fraction of the first piezoelectric ceramic and second piezoelectric ceramic is adjusted to suppress resonance frequency fluctuation relative to change in vibration speed. |