| In this paper, a B-site precursor method (or two-step calcinations method) was adopted in the preparation of the Pb(Zr0.5Ti0.5)-Pb(Mg1/3Nb2/3)O3 piezoelectric ceramics ternary system. The effect of the sintering conditions and PMN composition on dielectric and piezoelectric properties was investigated. Small amout of Nb2+ was then added to this system as doping to improve the properties. X-ray diffraction indicated that there is only a single phase of ZrTiO4 crystal present for x≤0.3 in the B-site precursor, (Zr0.5Ti0.5)1-x(Nb2/3Mg1/3)xO2, calcined twice at 1350℃. XRD was also applied to identify the perovskite phase. It was found the optimum calcinations condition of perovskite-phase was above 750℃. The sintering temperature decreased with the increasing of composition x and the optimum sintering temperature was about 1150℃ when x was in the range of 0.05~0.15. High piezoelectric and dielectric properties were obtained when the compositions of x were in the tetragonal region near the morphotropic phase boundary (MPB) in phase diagram. Nb5+ was added to the system and When doping amount was 0.02mol, the optimal results of εr = 1227,tanδ =0.0256, Kp = 0.637, d33 = 338×10-12C·N-1 are obtained., but when more Nb5+ was added, the system had a trend of decreasing because of bringing excessive O2+ vacancies. A-site precursor,(Pb1-xSrx)CO3, was prepared by forced coprecipitation method. It can be seen by SEM that the equivalent diameter of rod-typed particle of precursor was about 200nm. So "double-precursor" method was used when it was added to the B-site precursor to form strontium substituting system, the dielectric properties increased distinctly but the piezoelectric properties were not optimal. It may due to the low polarization voltage caused by the high sintering temperature.
|
PDF Full Text Request