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A set of composite PbZr0.53Ti0.47O3 − xPb2Ru2O6.5 (PZT 53/47 − xPRO) and pure PbZr0.53Ti0.47O3 (PZT 53/47), PbZr0.38Ti0.62O3 (PZT 38/62) and PbZr0.36Ti0.64O3 (PZT 36/64) thick films (thicknesses 20–30 µm, porosity 25–50%) prepared by screen printing on (0001) single-crystal sapphire substrates, were studied using Fourier-transform infrared (FTIR) reflectivity and time-domain terahertz transmission spectroscopy. The compositions studied with 10, 15, 20 and 25 vol% PRO were around the electrical percolation threshold in the bulk ceramic composites (~17 vol%), known from impedance spectroscopy by Bobnar et al (2008 Appl. Phys. Lett. 92 182911). To obtain the effective dielectric functions of the films, we accounted for their porosity by using the Lichtenecker model. Using the dielectric functions of bulk pure PZT 53/47 ceramics and PRO single crystals from the literature available, effective dielectric functions were compared with those obtained using the generalized effective medium model by McLachlan with percolation threshold and critical percolation exponents, which fit the low-frequency data by Bobnar et al. The effective dynamic response in all the samples was dominated by an overdamped THz conductivity peak (central mode), as in pure PZT. The percolation threshold was not particularly apparent in the polar-phonon frequency range as it characterized the localized response. Unlike the low-frequency permittivity, which diverged at the percolation threshold, the effective microwave–terahertz permittivity increased above it.

The properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (0.65PMN–0.35PT) thick films were studied for high-frequency piezoelectric transducer applications. The films were prepared by screen-printing a thick-film paste on platinized alumina substrates and subsequent sintering at 950 °C. The effective thickness-coupling factor of these films was close to 48%, which is comparable with bulk ceramics having the same compositions. Furthermore, simulations of two configurations representing one element of a high-frequency linear-array transducer (30 MHz) suggests that 0.65PMN–0.35PT thick-films in 50 Ω electrical matching environment improves the performance in comparison with standard Pb(Zr,Ti)O3 (PZT) compositions.

The effects of the poling field on the structural and electrical properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (0.65PMN–0.35PT) ceramics were investigated. The highest piezoelectric coefficient d 33, coupling coefficients k p, k t, and mechanical quality factor Q m were achieved for ceramics poled at electric fields between 2 and 3.5 kV/mm, whereas the d 33, k p, k t, and Q m of ceramics poled at higher electric fields, i.e., 4 and 4.5 kV/mm, were lower. The non-poled ceramics contained 86% of the monoclinic phase with the space group P m and 14% of the tetragonal phase with the space group P4m m. However, the ceramics poled at 2.5 kV/mm contained 99% of the monoclinic phase and the rest is the tetragonal phase. The results show that the ratio of the monoclinic to the tetragonal phases can be changed by the application of a poling electric field and that the extent of this change is dependent on the field strength.