The measurements of the direct piezoelectric d33 response of BiFeO3 revealed considerable piezoelectric nonlinearity, that is, dependence of the d33 upon the stress amplitude, which we attribute to the irreversible non-180° domain wall contribution. We showed that this contribution may constitute up to 38% of the total measured d33, which is comparable relatively to what has been measured in Pb-based ferroelectrics, such Pb(Zr,Ti)O3 (PZT). The nonlinear piezoelectric response of BiFeO3, however, showed a frequency dependence that is qualitatively different from that measured in, e.g., PZT, possibly indicating the presence of charged domain walls.
COBISS.SI-ID: 26122791
Complex non-180◦ domain configurations with strong variations in characteristic length (from micrometre size down to the nanoscale) and morphology were found in 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 thick films. This strong variation in domain configurations is most probably the result of the slowing down of the kinetics of the relaxor to ferroelectric transition on approaching a grain size around the micrometre, an effect previously reported for bulk ceramics and that results in the stabilization of sub-micrometre and nanoscale intermediate domain configurations. Nevertheless, also the influence of the in-plane compressive stress exerted by the substrate on the domain structure was studied.
COBISS.SI-ID: 25895463
Lead-free potassium sodium niobate (K0.5Na0.5)NbO3 thin films on Pt(111)/TiO2/SiO2/Si substrates have been prepared from the acetate–alkoxide-based precursor solutions with the stoichiometric composition and with 5 or 10 mol% excess of sodium or potassium acetate. Upon heating to 750°C, the films crystallize in pure perovskite phase. The increasing amount of alkali excess in solutions increases the degree of {100} orientation and it influences the nucleation and growth processes in the films. The microstructure of about 250 nm thick films prepared from the stoichiometric and 5 mol% excess solutions consists of equiaxed grains of about 50 nm across, whereas the grain size in the about 220 nm thick films prepared from the 10 mol% excess solutions is about 200 nm. The chemical composition of the films prepared from the 5% potassium-excess solution was closest to the (K0.5Na0.5)NbO3 composition among all the samples as determined by SEM-EDXS. These films had the room temperature values of dielectric permittivity, dielectric losses, remnant polarization, and coercive field measured at 1 kHz 610, 0.015, 8 µC/cm2, and 80 kV/cm, respectively.
COBISS.SI-ID: 25198631
Homogeneous lead–zirconate–titanate (PZT) thick films were fabricated by an electrophoretic deposition (EPD) process for high-frequency ultrasound applications. PZT and PbO particles stabilised with polyacrylic acid in an ethanol were deposited on a platinized alumina substrate at a constant-current mode and sintered. 15 to 20 % of pores in the thick films that are tailored by deposition and sintering conditions, improve their electromechanical performance what was confirmed by the model. With EPD process we fabricated a PZT thick film with a thickness of ~30 μm, a density of ~80% and a thickness coupling factor of 48%. These results indicated that EPD process is suitable for the fabrication of efficient, high-frequency transducers operating at frequencies above 40 MHz.
COBISS.SI-ID: 25227815