Piezoelectric/electrostrictive actuator having integral ceramic base member and film-type piezoelectric/electrostrictive element (S)

A piezoelectric/electrostrictive actuator comprising:

• a ceramic base member in which at least one pressure chamber is formed, said ceramic base member consisting of a spacer plate having at least one window which provides said at least one pressure chamber, respectively, a closure plate disposed on one of opposite major surfaces of said spacer plate, for closing one of opposite openings of each of said at least one window, and a connecting plate disposed on the other major surface of said spacer plate, for closing the other opening of said each window, said connecting plate having at least one hole formed in alignment with said at least one window, respectively, said connecting plate having an outer surface remote from said spacer plate, said outer surface having maximum waviness of not larger than 50 .mu.m per reference length of 8 mm, said spacer plate, said closure plate and said connecting plate being formed from respective first, second and third ceramic green sheets which are laminated on each other and fired into an integral ceramic structure as said ceramic base member, the at least one hole of the connecting plate being formed through the thickness of the third ceramic green sheet, and the at least one window being formed through the thickness of the first ceramic green sheet;
• and
• at least one piezoelectric/electrostrictive element each disposed on a wall partially defining the corresponding one of said at least one pressure chamber, for deforming said wall so as to change a pressure of the corresponding pressure chamber, each of said at least one piezoelectric/electrostrictive element comprising a piezoelectric/electrostrictive unit consisting of a pair of electrodes and a piezoelectric/electrostrictive layer, which are formed by a thick-film forming method on an outer surface of said closure plate of said ceramic base member, or on an outer surface of the second ceramic green sheet which forms said closure plate, such that said piezoelectric/electrostrictive layer is interposed between said pair of electrodes.