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 Pb-1.01{(Mg1.3Nb2.3)(0.025)(Zr0.825Ti0.175)(0.975)}(1-z)UzO3 (Whatmore, RM., UK Patent GB2347416A, 2001). Good pyroelectric properties have been obtained for this system, with a pyroelectric coefficient of 3x10(-4) Cm-2 K-1 at z=0.006. and corresponding pyroelectric figures of merit of F-V=0.066 m(2) C-1 and F-D=4.7x10(-5) Pa-1 (2). It was found that the DC resistivity varied from 1.2x10(10) Ohmm for z=0.0048 to 1 x 10(8) Ohmm for z=0.0145 in a highly predictable fashion, such that the DC conductivity/doping law was accurately described by the equation: sigma(o) =A exp(-alphaaz(-1 3)-E-a/kT) with alpha = 0.63 Angstrom(-1) and E-a=0.28 +/- 0.04eV. 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. (C) 2002 Elsevier Science Ltd. All rights reserved.