Improvements to pyroelectric ceramics via strontium doping of the lead zirconate-lead iron niobate-lead titanate system

Abstract

Pyroelectric ceramics with the starting composition:

Pb_1.02-α/100Sr_α/100(Zr_0.58Fe_0.20Nb_0.20Ti_0.02)_0.995U_0.005O₃

where α is in the range 0–8, were fabricated via the hot-pressing of mixed oxide powders. With increasing values of α, it was found that the Curie temperature decreased and the room temperature dielectric constant (E _r ) and pyroelectric coefficient p(T) increased. The figure of merit F_D , which maximises detectivity, had a peak value of 6.0 × 10⁻⁵Pa^−1/2 when α = 4. This composition had a dielectric loss, ε _r and p(T) values of 0.28%, 398 and 4.9 × 10⁻⁴ Cm⁻²K⁻¹ respectively at room temperature and 1592 Hz, with a minimum in loss at 5 × 10³ Hz. The grain size of these ceramics was found to be highly dependent on the level of Sr substitution; for a values greater than 2, a coarse (12 μm) grain structure was observed at the edges of the ceramic wafers and this gradually decreased to a grain size of 5 μm in the centre. Possible causes for this microstructural effect are discussed. The ferroelectric domain structures for these ceramics in the unpoled, partially poled and fully poled states are also reported.