Eletrical conductivity control in uranium-doped PbZrO₃-PbTiO₃-Pb(Mg_1/3Nb_2/3)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 {(Mg_1/3Nb_2/3)_0.025(Zr_0.825Ti _0.175)_0.975} _1-zU_zO₃ (Whatmore, R.W., UK Patent GB2347416A, 2001). Good pyroelectric properties have been obtained for this system, with a pyroelectric coefficient of 3×10^-4Cm ^-2 K^-1 at z=0.006, and corresponding pyroelectric figures of merit of F_v=0.066 m²C^-1 and F_D=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: σ_o=A exp(-αaz^-1/3-E_a/kT) with α=0.63 Å^-1 and E_a=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.