| abstract |
The present invention provides a piezoelectric actuator that enjoys excellent practicality. n The piezoelectric actuator includes a piezoelectric element ( 2 ) including a sheet of piezoelectric ceramic and electrodes formed at least part of the surface of the sheet of piezoelectric ceramic, and a holding member ( 4 ) holding the piezoelectric element ( 2 ). The piezoelectric at least one of the requirements (a) to (e) described below. n (a) The bulk density shall be equal to or smaller than 5 g/cm 3 , and the Young's modulus Y 11 E calculated according to a resonance-antiresonance method shall be equal to or larger than 90 GPa. (b) The coefficient of thermal conductivity shall be equal to or larger than 2 Wm −1 K −1 . (c) The coefficient of thermal expansion shall be equal to or larger than 3.0 ppm/° C. over a temperature range from −30° C. to 160° C. (d) The pyroelectric coefficient shall be equal to or smaller than 400 μCm −2 K −1 over the temperature range from −30° C. to 160° C. (e) The mechanical quality factor Qm calculated according to the resonance-antiresonance method shall be equal to or smaller than 50 over a temperature range from −30° C. to 80° C. |