Electrical conductivity control in uranium-doped PbZrO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 pyroelectric ceramics

The effects of uranium doping on the electrical conductivity and pyroelectric/dielectric properties of lead zirconate–lead titanate–lead magnesium niobate (PZ–PT–PMN) ferroelectric ceramics have been investigated. These ceramics have the general formula Pb1.01{(Mg1/3Nb2/3)0.025(Zr0.825Ti0.175)0.975}1−zUzO3 (Whatmore, R.W., UK Patent GB2347416A, 2001). Good pyroelectric properties have been obtained for this system, with a pyroelectric coefficient of 3×10−4 Cm−2 K−1 at z=0.006, and corresponding pyroelectric figures of merit of FV=0.066 m2 C−1 and FD=4.7×10−5 Pa−1/2. It was found that the DC resistivity varied from 1.2×1010 Ωm for z=0.0048 to 1×108 Ωm for z=0.0145 in a highly predictable fashion, such that the DC conductivity/doping law was accurately described by the equation: σo=A exp(−αaz−1/3−Ea/kT) with α=0.63 Å−1 and Ea=0.28±0.04 eV. This conductivity law corresponds very closely to that reported previously for uranium-doped ceramics in the lead zirconate–lead titanate–lead iron niobate system. This implied a similar conduction mechanism, probably hopping between non-ionised dopant ion sites. It is demonstrated that this relationship can be used as a predictive tool for electrical conductivity control in these systems.