PIEZOELECTRIC ELEMENT AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide a thin piezoelectric element which has high frequency and can secure its stable temperature characteristic as designed by laminating two types of piezoelectric ceramics having positive and negative temperature change rates respectively in regard to the traveling velocity of an elastic wave. SOLUTION: The piezoelectric ceramics A having the positive temperature change rates of elastic wave traveling velocities and the piezoelectric ceramics B having the negative temperature change rates of elastic wave traveling velocities are periodically laminated together. That is, the ceramic material powder is burnt and crushed and then mixed into a 2-propanol solvent. These material powders are laminated into a sheet form. In such cases, a composition A contains Pb(Mg1/3 Nb2/3 )0.125 Ti0.435 Zr0.44 O3 and a composition B contains Pb(Mg1/3 Nb2/3 )0.375 Ti0.375 Zr0.25 O3 . Then the layers 1 of 50μm containing composition A and the layers 2 of 20μm containing composition B are periodically laminated together. This lamination structure of layers 1 and 2 is heated in the air at 700 deg.C and for 5 hours and then burnt in an oxygenic atmosphere at 950 deg.C and for 5 hours. Then a copper elastic wave exciting electrode 3 and an elastic wave receiving electrode 4 are baked onto the lamination structure to complete the treatment. As a result, the center frequency change rate is reduced and the temperature characteristic is stabilized.