Dielectric and piezoelectric properties of (La, Mg, F) and (Mg, Mn, F) doped PZT ceramics under low and high sollicitations

The hysteretic behavior of the charge coefficient d(33) under high mechanical stress and of frequency constant N-33 during the temperature cycle -40 degreesC- + 80 degreesC can be cancelled by fluorine oxygen substitution in the lattice of Mg-doped PZT. These fluorine doped materials also exhibit a high mechanical quality factor and low dielectric losses. The drawback is that they have a lower d(33) coefficient and are difficult to pole. Mn doping in B site or La doping in A site, in the ABO(3) type perovskite structure are known to increase the d(33) coefficient and the poling ability. This result is observed on (Mg, F) co-doped PZT with Mn and with La content of 1.5 mol%. In the same manner, Mn doping enhances the hysteretic behavior and the losses while La doping does not significally changes the (Mg, F) co-doped PZT characteristics except the fluorine content for which the losses and the hysteresis are the lowest. (C) 2001 Elsevier Science Ltd. All rights reserved.