Characteristics of F doped PZT ceramics using different fluorine sources

In this study, some structural and electrical properties of a PZT base composition Pb0.89(Ba, Sr)0.11(Zr0.52Ti0.48)O3 co-doped with 1 mol% manganese and 2 mol% fluorine have been studied. Two different fluorine sources were used: lead fluoride PbF2 and manganese fluoride MnF2. These fluoride salts are added to the co-precipitated precursors powder. Mn dopant was added to the solution as manganese acetate (MnAc) before co-precipitation, when PbF2 was used. The structural analysis of the sintered ceramics revealed that MnF2 doping makes the volume of the cubic unit cell (Vc) and the grain size decrease, whereas (MnAc, PbF2) co-doping makes the apparent density increase and keeps the average grain size and Vc unchanged. Both types of doping reagents largely enhance the piezoelectric activity (high d33 and k33 coefficients, well saturated Polarization–Electric field loops) but MnF2 induces both combinatory soft and hard characteristics compared to (MnAc, PbF2) co-doping. Impedance spectroscopy showed that both types of doping reagents strongly reduce the electrical conductivity with the same conducting species, i.e. the same defect chemistry, confirmed by optical absorption data. Finally, this study shows that in the semi-wet process used, PbF2 is added homogeneously to the co-precipitated powder. Whatever the fluorine source, only the coexistence of Mn and F dopants is necessary to improve the piezoelectric response.