Development of piezoelectric ceramics for ultrasonic motor applications

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2011
Kalem, Volkan
This study has been carried out to develop and manufacture piezoelectric ceramic materials which are utilized for ultrasonic motor (USM) applications. For this purpose, the effect of compositional modifications on the dielectric and piezoelectric properties of lead zirconate titanate (PZT) based ceramics was investigated. PZT based powders were produced using the mixed oxide method. The base composition was selected as Pb(Zr0.54Ti0.46)O3. The samples in the proximity of morphotrophic phase boundary were doped with strontium, lanthanum, lead manganese niobate (PMnN) and lead manganese antimonate (PMS) in order to improve the structural characteristics and electromechanical properties which are very important for USM applications. The dielectric constant, planar coupling coefficient, mechanical quality factor, piezoelectric strain constant and tangent loss values were evaluated in accordance with standard IRE (Institute of Radio Engineers) test procedures. The results on dielectric and piezoelectric properties showed that piezoelectric ceramics with high mechanical quality factor, high piezoelectric strain constant and low tangent loss could be produced by using the aforementioned dopants. As a result, a new piezoelectric ceramic named as 0.97[PSLZT]-0.024[PMnN]-0.006[PMS] was produced with KT= 1913, Qm= 1240, d33= 540 pC/N, tan delta= 0.89%, kp= 0.57 and Tc= 235 °C. This composition is a good candidate for high power applications. The ceramic samples with the developed compositions were used to produce an ultrasonic-wave type motor and the performance of the USM was evaluated in terms of speed, torque and efficiency.