[en] Piezoelectric ceramics currently provide the key functional element in devices in an exceptionally wide range of applications, including transducers, sensors, and signal processing and voltage transformers. The material of choice for the a majority of these applications has been polycrystalline ceramics based on Pb(Zr,Ti)O₃ (PZT). The unique properties of piezoelectric that can sense and actuate simultaneously makes this materials interesting also in thick modules. Paper present an overview of recent results concerning the integration issues of PZT based materials on various substrates, their solutions and potential applications for sensors and actuators. Common processing temperatures to get dense PZT ceramics are around 1200^oC. To reach temperature between 800-900^oC basic compositions should be modified by additives forming liquid at these temperatures. Guidelines for choice are given. The major issue in processing of thick film structures containing PZT is to suppress reaction between PZT film and substrate driven by high chemical potential of PbO in PZT. Therefore the efficient barrier layers on alumina silicon and LTCC are discussed. (author)

[en] The crystal structure of a new oxide, La₂RuO₅, was determined ab initio using conventional laboratory X-ray powder diffraction. Combining X-ray and electron diffraction techniques, we found that the new phase crystallized in the monoclinic system with the space group P2₁/c (SG no.14) and the cell parameters a=9.1878(2) A, b=5.8313(2) A, c=7.9575(2) A and β=100.773(2) deg. (V=418.8 A³, Z=4). The structural determination with the Patterson method and Fourier difference syntheses and the final Rietveld refinement were performed by means of the JANA2000 program. The structure is built up from the regular stacking of a two octahedra thick [LaRuO₄]_∞ zigzag perovskite slab and an original ∼3.4 A thick [LaO]_∞ slab which constitutes the key feature of this new structure

[en] 1. Thermal behaviour of Ca₃UO₆, Ca₂UO₅, CaUO₄, Ca₂U₃O₁₁ and CaU₂O₇ was studied by DTA, quasiisothermal thermogravimetry and the quenching technique up to 1400⁰C in air and oxygen. The temperatures of reactions were determined and the reaction products were identified by the X-ray technique. 2. All reaction temperatures strongly depend on oxygen partial pressure and are lower in air than in oxygen. (orig.)

[en] Phase transitions of sodium niobate, prepared by the solid state synthesis method, were examined using dielectric measurements, differential scanning calorimetry, and high temperature x-ray diffraction, in order to contribute to the clarification of its structural behavior below 400 deg. C. Four phase transitions were detected in the ceramic sample using dielectric measurements and differential scanning calorimetry and the obtained temperatures were in a good agreement with previous reports for the transitions of the P polymorph. The anomaly observed by dielectric measurements in the vicinity of 150 deg. C was frequency dependent and could be related to the dynamics of the ferroelectric nanoregions. The phase transitions of the as-synthesized NaNbO₃ powder were investigated using differential scanning calorimetry and high temperature x-ray diffraction. The results show the existence of the Q polymorph at room temperature, not previously reported for the powder, which undergoes a transition to the R polymorph upon heating through a temperature region between 265 and 326.5 deg. C. This transition is mainly related to the displacement of Na into a more symmetric position and a minor change in the tilting system. The structures at room temperature, 250, 300, and 420 deg. C were refined by the Rietveld method and the evolution of the tilting system of the octahedral network and cationic displacement are reported.

[en] Homogeneity of the amorphous sol-gel precursors of Pb(Zr,Ti)O₃ ferroelectric ceramics is studied at various Zr/Ti ratios. From Zr K-edge EXAFS spectra the immediate vicinity of Zr atoms is determined. A distorted octahedron of O atoms with all the bonds continued in Zr-O-Zr links is observed down to Zr/Ti ratio of 1:1, indicating the prevalent homocondensation of Zr. In the precursor with Zr/Ti ratio of 25/75 a smaller distortion of O octahedra is observed and heterometallic bonding Zr-O-Ti is found. Mixing of the two metals (Zr, Ti) at molecular level is thus established at low Zr/Ti ratios. (au)

[en] 0.5Pb(Zr_0.575Ti_0.425)O₃-0.5Pb(Fe_2/3W_1/3)O₃ (0.5PZT-0.5PFW) belongs to the solid solutions which exhibits some bi-relaxor properties, with both ferroelectric and magnetic relaxor properties. Recently it was reported that the thin film of 0.8Pb(Zr_0.53Ti_0.47)O₃-0.2Pb(Fe_2/3W_1/3)O₃ (0.8PZT-0.2PFW) has a new and very large magnetoelectric effect-switching from P_r to zero with applied magnetic field of less than a Tesla. We report dielectric and ac electric conductivity investigations of the 0.5PZT-0.5PFW bulk ceramics. A detailed analysis of the temperature dependence of the universal dielectric response parameter s in terms of the theoretical model for tunneling of small polarons revealed that below 450 K this mechanism governs the charge transport in the system. This provides a new understanding of the magnetoelectric effect in 0.5PZT-0.5PFW.

[en] The spatial distribution of the out-of-plane and in-plane components of ferroelectric polarization in (1 - x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ thick films with x = 0.35 on Al₂O₃ substrates has been studied by piezoresponse force microscopy. Complex non-180° domain configurations with strong variations in characteristic length (from micrometre size down to the nanoscale) and morphology are found. This 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 submicrometre and nanoscale intermediate domain configurations. Nevertheless, fluctuations of the in-plane compressive stress exerted by the substrate must exist and play a role, as indicated by in-plane polarization regions next to grain boundaries. Film stress might also be responsible for conventional 180° domains not being found, and for the appearance of 180° superdomain bands formed from bundles of submicrometre-size non-180° domains instead, as previously described in Pb(Zr,Ti)O₃ films. Also, the presence of polar nanodomains and the possibility of them being observed are addressed. Finally, the mobility of non-180° domain walls under electric fields is clearly demonstrated, which is the key to relatively high electromechanical response in films. (paper)

[en] The analytical partial capacitance methods (PCM) widely accepted for calculation of properties of capacitors with planar electrodes, coplanar strip waveguides (CPS) and coplanar waveguides (CPW) are reviewed based on the challenges met during the development and tailoring of (Ba, Sr)TiO₃ thin films fabricated on different types of substrates. An alternative view on the conformal mapping method is given, a correction for electrodes of finite thickness is introduced and the applicability of easy-to-use simplified analytical equations is reviewed and extended. Calculation results obtained with different models are compared against the results of FEM numerical simulation in the parameter range relevant for development of tuneable ferroelectric films. The models were found to be less accurate than previously reported. Accordingly, guidelines for extending the applicability domain and for minimizing the inherent errors of the analytical models are presented. The discussion is focused on the possible improvements of the measurement techniques

[en] The Raman spectra of the ceramics PLZT x/40/60 have been measured in the temperature range 20-800 K. An assignment of the Raman modes is presented using the results of the effective medium approximation for the IR data. Factor-group analysis is presented for the case of off-site position of cations or unit cell doubling, which allows a higher number of active phonons in the IR and Raman spectra. The presence of Raman-active modes in the cubic phase is associated with local unit cell doubling and symmetry breakdown due to the off-site cations

[en] The polarization switching is experimentally investigated in hot-pressed PLZT-x/65/35 ceramics with lanthanum content from 5 to 12 at. %. The specific features in the temperature dependence of the polarization switching in a heterophase state are interpreted by analyzing the change in the switched charge measured over wide ranges of fields and temperatures. Particular emphasis is placed on the role of depolarization fields induced by interphase boundaries. A model of the evolution of polydomain nanostructures with a change in the temperature and in the response to an external field is considered. It is assumed that the low-temperature dielectric anomaly and the temperature hysteresis are associated with the loss of stability of a large-scale domain structure and its transformation into a nanodomain state