Complex non-180° domain configurations with strong variations in the characteristic length (from micrometre size down to the nanoscale) and morphology were found in 0.65Pb(Mg1/3Nb2/3)O3 - 0.35PbTiO3 (PMN-PT) thick films. The study was done on textured films on the matrix area, away from the grown areas. This strong variation in domain configurations is most probably the result of the slowing down of the kinetics of the relaxor/toferroelectric transition on approaching a grain size around a micrometre, an effect previously reported for bulk ceramics, which results in the stabilization of submicrometre and nanoscale intermediate domain configurations. In addition, the influence of the in-plane compressive stress exerted by the substrate on the domain structure was studied as well.
COBISS.SI-ID: 25895463
We prepared textured Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics by templated grain growth approach (TGG). The ceramics was synthesized from a powder prepared by mechanochemical activation, that is, in a similar way as the partially textured thick films studied in the frame of this project. Also the templates were prepared in the same way as the templates used in thick films, i.e., by exaggerated grain growth approach. We found out that the ceramics exhibited the highest texture and the best functional properties when it was prepared by templates of an average size of approximately 30 microns, which is larger than the templates used for the thick films. These templates could not be used in the preparation of the textured thick films, because the thickness of the films prepared by screen-printing was less than 100 microns and hence the templates would occupy the major part of the films and the growth around the templates would not occur. Therefore, for the preparation of thick films the 10 micron templates were used.
COBISS.SI-ID: 27373095
We have prepared and characterized piezoelectric ultrasound transducers (UT) based on the PMN–PT non-textured thick films. The films showed outstanding properties for high-frequency applications. In the case of a linear-array transducer, the properties of the transducer based on the PMN–PT material were even superior to those based on the widely used PZT material.
COBISS.SI-ID: 26701607
In the framework of a systematic study, we presented the influence of the processing parameters, in particular, the presence of a packing powder during sintering and the sintering temperature on the microstructural and structural properties of potassium sodium niobate (K0.5Na0.5NbO3 or KNN) thick films. These KNN thick films were prepared with a 1 mass % addition of potassium sodium germanate (KNG), which serves as a liquid-phase sintering aid. The sintered films exhibited preferential crystallographic orientations along [100]pc and [10−1]pc directions, the origin of which lies in the compressive stresses developed during cooling as a result of the thermal expansion mismatch between the film and the substrate. In addition, the dielectric permittivity, dielectric losses and the piezoelectric d33 coefficient of the obtained films were compared with those of the KNN bulk ceramics.
COBISS.SI-ID: 27204135
Within the project we collaborated with Prof. Mamoru Senna from Keio Universtiy, Japan. During the visit of the professor at our department we developed a new synthesis method for the preparation of fine and single-phase K0.5Na0.5NbO3 (KNN) powders. The method consists of attrition milling of fine Nb2O5 particles suspended in an ethanol solution of sodium and potassium acetates. We obtained a single-phase KNN powder by calcining the milled powder twice at temperatures as low as 450-650°C, which are 100-200°C lower than those typically used during conventional solid-state synthesis of KNN. We believe this method could provide fine KNN powders that may be used for screen-printing of KNN thick films.
COBISS.SI-ID: 27355175