Kawatetsu Mining Co., Ltd.

Toshio Ogawa

Mitsuyoshi Matsushita

Yoshihito Tachi

A domain controlled piezoelectnc single crystal is disclosed which uses a lateral vibration mode for an electromechanical coupling factor k not less than 70% and a piezoelectric constant &minus;d not less than 1200 pC/N, with an electromechanical coupling factor k in the longitudinal vibration mode not less than 80% and a piezoelectric constant d not less than 800 pC/N. Also, a piezoelectric single crystal is disclosed which uses a high-performance longitudinal vibration mode with k not more than 30%. A fabrication method applies a DC electric field of 400 V/mm to 1500 V/mm for a maximum of two hours in a temperature range of 20&deg; C. to 200&deg; C. as polarization conditions in the thickness direction of the piezoelectric single crystal. The method can include cooling, or heating and cooling between temperature boundaries of rhombohedral and tetragonal crystals or between tetragonal and cubic crystals or within a cubic crystal temperature range.

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Fukuroi, Japan

Toshio Ogawa