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A series of microwave dielectric ceramics in the compositions of K2Mo2O7, K2Mo3O10, and K2Mo4O13 in K2O–MoO3 binary system with ultra low sintering temperatures were prepared using the solid-state reaction method. Their synthesis, phase composition, compatibility with metal electrodes, microstructures, and microwave dielectric properties were investigated. The K2Mo2O7 ceramic sintered at 460°C with a triclinic structure has a relative permittivity of 7.5, a Q × f value of 22 000 GHz, and a τf value of −63 ppm/°C. The X-ray diffraction patterns indicate that K2Mo2O7 does not react with Ag and Al electrodes at the co-fired temperatures. The K2Mo3O10 ceramic can be sintered well at 520°C with a relative permittivity of 5.6, a Q × f value of 35 830 GHz, and a τf value of −92 ppm/°C. It has compatibility with Ag electrode. The K2Mo4O13 ceramic sintered at 540°C possesses good microwave dielectric properties with a relative permittivity of 6.8, a Q × f value of 39 290 GHz and a τf value of −67 ppm/°C and it is compatible with Al electrode. For K2Mo2O7 and K2Mo4O13, it is found that the grain sizes and the number of grain boundaries play an important role in the dielectric loss. From this study, it can be seen that the three ceramics in K2O–MoO3 system have good microwave dielectric properties, ultra-low sintering temperatures, non-toxic, and low-cost characteristics. So they can be potentially applied to ultra-LTCC devices.

PurposeIn this manuscript the purpose is to present and evaluate the developed non‐destructive method for analysing the phase composition of LTCC Du Pont “Green Tape 951” material fired in the temperature range from 800 to 1,000°C using X‐ray powder diffraction and Rietveld refinement.Design/methodology/approachThe method uses the crystalline Al2O3 which is already present in the material as an internal standard since its mass fraction was previously found to be constant in the described temperature range.FindingsThe results of the non‐destructive analyses and the classical destructive analyses are comparable and the estimated error of the destructive phase analyses and the calculated errors for the non‐destructive phase analyses are of the same order.Practical implicationsThe described method can be used also for analysing another type of LTCC material. In this case it is necessary to check whether the mass fraction of any crystalline phase present in the sample is constant in the given temperature range, because only in this case can it be used as an internal standard for a determination of the phase composition.Originality/valueThe non‐destructive method is a fast and easy approach for analysing the fired samples and is also suitable for controlling the phase composition of LTCC materials on 3D complex structures without destroying them, just by using the X‐ray diffraction patterns collected from their surface.

The present work is a systematic study of the influence of the sintering conditions on the structural and electrical properties of 0.57Pb(Sc 1/2 Nb 1/2 )O 3 –0.43PbTiO 3 ceramics prepared from mechanochemically activated powder. The ceramics were sintered at various temperatures and for a range of times. Three or even more contributions competed for influence on the functional properties of the ceramics, i.e., the density, the grain size and the phase composition. However, all these contributions combined in such a way that the best functional properties were obtained for the ceramics sintered at 1000 °C for 8 h.

Composites from lead zirconate titanate (PZT) and yttria stabilized zirconia were manufactured to assess cracking and R-curve behavior in compact tension specimens. Additions of zirconia led to a reduction in PZT grain size and shifted the fracture behavior from intergranular fracture to intragranular fracture. The R-curves exhibited higher starting values, a steeper slope and a higher plateau value with increasing content of zirconia, albeit the effects on the toughness values were not more than 20%. The results are rationalized through increased crack tip toughness, reduced ferroelastic toughening and enhanced transformation toughening.

Lead-free (1−x) BaTiO3 –x BaMg1/3Nb2/3O3 ceramics with x = 0.03, 0.04, 0.05 and 0.06 were prepared by solid-state synthesis. The effects of the Ba(Mg1/3Nb2/3)O3 addition on the phase composition, dielectric and ferroelectric properties, as well as the electromechanical response of the classic ferroelectric BaTiO3 were investigated. The room-temperature X-ray diffraction analyses of all the ceramics revealed a perovskite phase after sintering at 1300 °C with a composition-dependent symmetry. The samples with a lower concentration of Ba(Mg1/3Nb2/3)O3, i.e., x = 0.03 and 0.04, were tetragonal, while the samples with x = 0.05 and 0.06 were found to be cubic. The result is in agreement with the dielectric, ferroelectric and electromechanical properties. With x increasing from 0.03 to 0.06 the temperature of the diffused maximum of the dielectric permittivity decreased from 348 K to 265 K. All the ceramics showed a large electromechanical response: the calculated room-temperature electrostrictive coefficient M 33 of the sample with x = 0.06 was 1.4 · 10−16 m2/V2, which is comparable to the value measured for Pb(Mg1/3Nb2/3)O3 ceramics.

For the fabrication of complex, micro-electromechanical systems (MEMS) devices based on low-temperature co-fired ceramic (LTCC), higher firing temperatures and longer times than those proposed by the LTCC producer are needed. These changes to the thermal budget may influence the material properties and consequently its functional properties. The effect of the firing conditions on the LTCC DuPont 951 and thus on the phase composition, that is, the alumina/anorthite ratio and porosity, on the mechanical properties is presented. The samples fired at low temperatures (800°C) had a high porosity (7%), which significantly contributed to the low elastic modulus (100 GPa) and the low mechanical strength of the LTCC (140 MPa). The samples fired at 850°C, which had only 1% of porosity, resulted in an elastic modulus of 122 GPa and a flexural strength of 224 MPa. A further increase in the temperature contributed to a slight decrease in the elastic modulus, while no significant difference in the flexural strength could be observed. The enhancement of the flexural strength with an increasing firing temperature was mainly related to a decrease in the porosity and to a lesser extent to the different ratio of the alumina/anorthite phases. The effect of firing time on the phase composition at selected temperatures (i.e., 100 h at 700 and 800°C) is also discussed.

Low-temperature co-fired ceramic (LTCC) is an important material in the production of ceramic multilayer structures. Large and complex multilayer structures are usually fired at higher temperatures and/or longer firing times compared to the relatively thin LTCC tapes. The firing conditions of LTCC determine the phase composition and the microstructure, which both influence the physical characteristics, such as the mechanical and thermal properties. In this work the effect of the phase composition on the biaxial flexural strength and the temperature coefficient of expansion of the DuPont 951 LTCC is presented. The samples were fired at different temperatures and times to obtain different phase compositions. The phase composition, especially the mass fraction of anorthite, was correlated with the biaxial flexural strength and the thermal coefficient of expansion (TCE). A very long firing time, i.e., 100h at 800 °C, yields, apart from crystalline anorthite, the cristobalite phase. The anorthite that crystalizes from the glass phase in a dense LTCC material changes the crack-propagation mechanism and improves the biaxial flexural strength of the material. The major change in the biaxial flexural strength is observed when the anorthite phase appeared. The increasing mass fraction of anorthite does improve the biaxial flexural strength less drastically. With the increasing mass fraction of the anorthite, decreases of the TCE of the material and a small decrease of the density of the LTCC material occur.

The combination of the quantitative texture analysis and Rietveld methods is used to study the preferential orientation of morphotropic phase boundary (MPB) Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics obtained by homogeneous Templated Grain Growth. Their complex structure, with the coexistence of several polymorphs, and the presence of texture that is required to take advantage of their excellent piezoelectric properties, raise serious problems for a precise characterization of these materials. Conventional methods of texture analysis, although simple, are limited, and the information obtained, if not studied with care, may be misleading. The use of linear detectors and χ-scan are more appropriate for the study of diffraction peaks with several contributions as it is the case for MPB compositions. This work shows the simultaneous determination of structural and texture parameters through the application of the so-called combined method, already used for the analysis of similar problems in a range of polycrystalline materials, to this specific case.

0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 powder was prepared by a single-step, solid-state synthesis at 850°C. This was enabled by the controlled agglomeration of precursor particles by the change of pH in water suspensions. With the design of the contacts between the particles in the agglomerates, a phase-pure perovskite powder was synthesized from a suspension with a pH = 12.5. At the inherent pH = 11.4, the agglomerates that promote the pyrochlore formation were formed, resulting in a mixture of perovskite and pyrochlore phases after the calcination. The ceramics prepared from the suspension with pH = 12.5 were sintered to 96% of theoretical density at only 950°C, and exhibited electrical properties comparable to ceramics prepared by the columbite method, sintered at much higher temperatures. In contrast, the properties of the ceramics from the pH = 11.4 suspension were heavily deteriorated due to the presence of the pyrochlore phase and the high degree of porosity.

The KTa0.6Nb0.4O3 sols for chemical solution deposition of thin films were prepared from potassium acetate and transition metal ethoxides by the 2-methoxyethanol based route. The local environment of both transition metals after reflux times 1, 4, 24, and 48 h, whereby the crystallization behavior of the films was strongly affected, was monitored by extended X-ray absorption fine structure spectroscopy, at Ta L3 and Nb K edges. The Ta species existed in the sols as monomers, remaining stable even with prolonged reflux time. The Ta–O–K correlations were confirmed in all cases. In contrast, the Nb-alkoxide formed dimers, with a gradual formation of oligomeric species with prolonged refluxing. The Nb–O–K correlations were present after all reflux times. The number of K neighbours around Nb increased upon refluxing, saturating at 24 h.

The electrocaloric effect (ECE) has recently become very attractive phenomenon due to its various potential applications, for example in heating or cooling devices of new generation which could be more efficient and environmentally friendly. Here a direct measurements of the ECE in thick films of 8/65/35 PLZT ceramics, and in the relaxor ferroelectric polymer composition P(VDF-TrFE-CFE)0.95-P(VDF-CTFE)0.05 near room temperature are presented. Our results are consistent with those obtained by indirect measurements. The maximum of the ECE responsivity ΔTEC/E in 8/65/35 PLZT thick films is achieved near the critical point, and in the terpolymer/copolymer blends it is shifted toward higher fields.

We report the processing of NaNbO3nanopowder by combining the solid-state synthesis and subsequent milling in the agitator bead mill. The effect of different rotation speeds of the agitator shaft on the comminution process was followed by laser granulometry. The morphology and specific surface area of the powders were investigated by scanning electron microscopy and the N2adsorption method, respectively. With the optimized milling parameters, we obtained NaNbO3nanoparticles with an average size of 25 nm and a narrow particle size distribution. The result is comparable to other processing techniques, such as solution-based chemical routes or mechanochemical synthesis; however, the presented method does not require any complicated processing and it can be easily upscaled to yield large quantities of the NaNbO3nanopowder. Furthermore, the compaction behaviour of the obtained nanopowder was investigated, and a compaction-response diagram was constructed revealing good compactability of the powder. The green compacts, isostatically pressed at 740 MPa, had a relative density of 70% and a narrow pore size distribution with an average pore radius of 4 nm.

Knudsen effusion mass spectrometry (KEMS) was used to determine the equilibrium vapour pressures of sodium over five selected compositions in different solid two-phase regions of the Na2O–Nb2O5 system at 1100–1470 K. The results were then used to determine the standard thermodynamic functions ( Δ f G T ° , Δ f H 298 K ° , S T ° ) of five solid compounds: Na3NbO4, NaNbO3, Na2Nb4O11, NaNb3O8 and NaNb13O33. These data were then incorporated into the IVTANTHERMO database to perform equilibrium calculations under real conditions relevant to the high temperature stability of sodium niobate, which is an important end member of the alkali niobate-based lead-free piezoelectric ceramics.

The electrocaloric (EC) effect attracted very recently considerable attention due to recent findings of the existence of a giant EC in polymeric and inorganic ferroelectric materials and because of its great potential in development of cooling or heating devices of new generation, which would be more environmentally friendly. A method and analysis of direct measurements of the large EC effect in self-standing [Pb(Mg1/3Nb2/3)O3]1-x[PbTiO3]x (PMN-xPT) with x = 0.35 thick ceramic films on a platinum layer are presented. Besides very large electrostrictive response already reported in these self-standing films, the experimental results confirm the existence of the large EC effect of similar magnitude as found in bulk PMN-0.35PT ceramics.

Presented in this paper of this special issue of Ferroelectrics, dedicated to Prof. Wolfgang Kleemann, is our recent study of thermal response near the dipolar glass to ferroelectric (G-F) transition studied by a high resolution calorimetry in relaxor ferroelectric 9/65/35 PLZT ceramics. By theoretical investigations based on spherical random bond random field (SRBRF) model it is predicted that the discontinuous electrocaloric change (EC) of temperature should be observed at the G-F transition line in an electric field–temperature (E-T) phase diagram. Experimental results confirm existence of such discontinuous EC jump in temperature in the canonical relaxor system 9/65/35 PLZT ceramics, thus confirming the existence of the first order G-F transition line in the E-T phase diagram of the perovskite relaxor ferroelectrics.

In this work the effect of firing temperature and firing time on the phase composition, microstructure, biaxial flexural strength, and temperature coefficient of expansion (TCE) of low-temperature cofired ceramic (LTCC) material is presented. At temperatures around 700°C the Al2O3 starts to dissolve in a low viscosity glass phase and this takes place up to 800°C, when 10 wt% of Al2O3 ceramic filler is dissolved in the glass phase forming the alumina-enriched area. This area is suitable for the crystallization of anorthite, which nucleates on the Al2O3 particles. The crystallization starts at 875°C and the mass fraction of anorthite increases with increasing temperature until it reaches a plateau value of around 22 wt% at higher temperatures or longer firing times. The biaxial flexural strength of the LTCC increases with increasing firing temperature from 135 MPa (at 800°C) to around 300 MPa (at 900°C). The major effect on the biaxial flexural strength of LTCC is that of porosity. The effect of the amount of anorthite on the LTCC biaxial flexural strength is minor. The TCE of the LTCC decreases from 5.6 × 10−6 to 5.0 × 10−6 K−1 with increasing firing temperatures or times and it is correlated with the anorthite mass fraction, which crystallizes at the expense of a decreasing amount of glass phase in the LTCC.

In ceramic BaTiO3 thin film prepared by chemical solution deposition, the influence of small grain size (10–150 nm) and grain boundaries on ferroelectric behavior is investigated by the studies of low-frequency dielectric response. The apparent permittivity is suggested to result from an ensemble of grains possessing different properties and volume fractions, and having a nonferroelectric boundary layer. The effective permittivity of the boundary layer is found to be close to that of an interfacial layer in epitaxial thin-film ferroelectrics, indicating possible fundamental resemblance of these layers. The maximum effective permittivity of the grain interiors is estimated to be about 1500. The observed small intrinsic grain permittivity, small Curie constant, broad dielectric peaks, and high-temperature dielectric hysteresis are discussed in terms of size-induced changes of the phase diagram.

A near morphotropic phase boundary lead–magnesium–niobium titanate material system was synthesised by the sol–gel method; its thin films were deposited with or without nanoparticle (np) seeding and processed by the rapid thermal annealing. Influences of some process parameters and the np seeding on various properties of the resultant films were systematically investigated. Although no reduction in annealing temperature was achieved upon np seeding, the results indicated that nps might indeed play a role as nucleation centres during the crystallisation. All in all, the lead–magnesium–niobium titanate thin film system described here (particularly those annealed at higher temperatures) appeared to be suitable for its potential applications in wireless communication systems as ultrahigh dielectric constant e value capacitors; the unexposed film annealed at 750uC, for instance, exhibited the highest dielectric constant e (1425) with a low loss (loss tangent, y0?04) along with a strongly pronounced perovskite phase (96?5%).

The compositional dependent fracture behavior of soft PZT (Pb0.99Ba0.01(Zr1−xTix)0.98Nb0.02O3) ceramics in the vicinity of the morphotropic phase boundary was characterized using compact-tension specimens. The compositions with 0.40 ≤ x ≤ 0.55 displayed an increasing fracture resistance with crack extension (R-curve behavior). It was observed that the rhombohedral composition and the compositions near the morphotropic phase boundary showed the largest toughness enhancement. R-curve behavior was found to be influenced by the ferroelastic coercive stress, saturated remanent strain, and elastic modulus, which were experimentally measured for each composition. X-ray diffraction measurements were performed and compared to the fracture results to investigate the impact of phase and lattice distortion on ferroelastic toughening behavior.

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 energy dispersive X-ray spectroscopy revealed that the alkali excess in precursor solutions contributed to a higher level of chemical homogeneity of the films on the micrometer scale. 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 a result of more pronounced potassium losses upon heating. 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.

We present a general protocol for processing cost-beneficial, environmentally benign aqueous-type suspensions containing metal-oxide nanostructured particles, and their patterning with piezoelectric ink-jet printing technology. The critical issues relevant to ink-jet printing are the preparation and stabilization of nanosized particles in a fluid and adjusting its physical properties to the values appropriate for a particular ink-jet printer mechanism. We discuss and illustrate, on a model titania system, the processing of a highly stable, colloidal, water-based suspension containing particles not bigger than 570 nm, prepared by a ball-milling process. For the ink-jet printing experiments, the surface tension and the viscosity of the suspension were modified by the addition of a small amount of the appropriate non-ionic amphiphiles and glycerol. The formation of droplets, their positioning on the substrate, and the shape and uniformity of the dots on the substrate are discussed and correlated with the fluid properties via the inverse Ohnesorge number Z. It was shown successfully that uniform, regular-shaped TiO2 dots with a diameter of 30 μm and a good positioning accuracy on Si/SiO2 substrates could be obtained by jetting a fluid with Z values of 5 and 9 using a piezoelectric ink-jet printer with a nozzle diameter of 21 μm operating at an amplitude of 13 V and a frequency of 5 kHz.

In this work, the effect of introducing tetragonal yttria-stabilized zirconia (TZ) particles in soft [Pb0.98Ba0.01][(Zr0.53Ti0.47)(0.98)Nb-0.02]O-3 (PZT) was investigated. Both microstructure and electrical properties of the PZT-xTZ (x = 0, 2, 5, 10, 20 vol%) composites were studied and correlated. The addition of zirconia hinders the matrix grain growth, resulting in smaller grains. According to X-ray diffraction analysis, zirconia containing composites have a higher rhombohedral-to-tetragonal phase ratio, in addition to lower dielectric and piezoelectric properties, in comparison to pure PZT. Electrical properties, in terms of strain- and polarization-electric field hysteresis curves, are presented and correlated with the observed phase compositions and microstructures. The extrinsic contribution to the piezoelectric properties in PZT and PZT-xTZ was studied by measuring the frequency and the stress field amplitude dependences of the piezoelectric d(33) coefficient.

A general approach to prepare aqueous suspensions of inorganic particles suitable for ink-jet printing was developed. Titanium dioxide was used as the model material. Stable colloidal suspensions of TiO2 particles in water were prepared by adjusting the pH. The milling conditions were optimized in order to effectively mill the starting micron-sized powder. After 280 min of milling, the particle size was decreased to dmean = 170 nm. The fluid properties of the suspensions, i.e. viscosity and surface tension, were optimized by increasing the solid load of TiO2 powder and by addition of the surfactant triton X-100. Additionally, glycerol was added to the suspensions to control the drying behavior. The patterns of TiO2 were successfully printed on glass substrates.

A detailed study of the macroscopic and microscopic behavior upon sintering of sodium niobate was carried out. A dynamic sintering curve, recorded at a constant heating rate of 5°C/min up to 1412°C, supported by the microstructural analysis of the samples, quenched at selected temperatures, revealed a multiple-stage densification. This was connected with the activation of different material-transport mechanisms: evaporation/condensation and surface diffusion up to 950°C, and other diffusion mechanisms, which contribute to both shrinkage and grain growth at higher temperatures. The second series of quenching experiments was used to track the microstructure development during the isothermal heating stage of the sintering process at 1350°C. The change from a fine-grained microstructure, with an average grain size of 2.53 ± 1.1 μm, to a coarse-grained microstructure, with an average grain size of 35.6 ± 32 μm occurred after isothermal sintering for 30 min. The first entrapped pores within the large grains of several 10 μm indicated the increased grain-boundary migration velocity already after 15 min of sintering. These conditions were identified as the onset point for abnormal grain growth in sodium niobate.

The influence of preparation conditions on dielectric properties of CaCu3Ti4O12 (CCTO) thin films was studied by detailed dielectric investigations in a broad temperature and frequency ranges. Experimental results, obtained in various CCTO thin films prepared by chemical solution deposition, and analysis in terms of the equivalent circuit reveal that the preparation conditions govern the distinctive contributions of insulating grain boundaries and semiconducting grains in different temperature and frequency ranges. With proper postannealing process, dielectric constant of ≈3000 was obtained in films with thickness below 500 nm. In addition, the electrical conductivity results reveal that one-dimensional variable range hopping is the dominating transport mechanism in CCTO thin films.

We have studied the mechanochemical reactions between Na 2 CO 3 and the transition-metal oxides M 2 O 5 (M = V, Nb, Ta), giving special attention to the course of the individual reaction and to the influence of the transition-metal oxide on the reaction rate. A common mechanism links the studied reactions and is characterized by the formation of an intermediate amorphous carbonato complex, in which the CO 3 2– ions that are present initially in the Na 2 CO 3 , coordinate to the transition-metal cation. In a subsequent milling stage the carbonato complex decomposes, leading to the formation of the final binary compounds, i.e., NaVO 3 , NaNbO 3 and NaTaO 3 . Quantitative experimental results, based on the Rietveld refinement method and thermogravimetric analyses, showed that the reaction rate follows the order Na 2 CO 3 + V 2 O 5 > Na 2 CO 3 + Ta 2 O 5 > Na 2 CO 3 + Nb 2 O 5 . By analyzing the acid–base properties of the participating reagents, we found that the experimental observations agree with the acid–base interaction mechanism, which means that the larger the acidity of the transition-metal cation involved, the faster and more complete the mechanochemical reaction. Finally, it was found that only partial decomposition of the carbonato complex, even after a prolonged mechanochemical treatment, can be expected in reactions characterized by lower acid–base potential.

We developed a new, simple method to prepare pure perovskite Pb(Mg1/3Nb2/3)O3 (PMN) from an aqueous suspension in a single annealing step. In this synthesis it is crucial to suppress the reaction between PbO and Nb2O5, which leads to secondary pyrochlore PbxNbyOz phases. Our method is based on the designed arrangement of particles of the starting compounds. The self-assembly of the colloidal aggregates was governed by particle surface charge, which was adjusted by the suspension pH. At pH below 11.8 particle–particle interactions lead to close contacts between lead oxide and niobium oxide particles in the suspension as well as in the dried powders, whereas at pH above 11.8 close contacts between lead and niobium oxide particles are avoided. The suspensions of the starting powders were prepared at pH 10.0, 11.4, 12.5, and in acetone. After heating of the dried suspension with the pH set at 12.5 at 900°C, a pure perovskite PMN powder was obtained. On the contrary, the powders prepared from the pH 11.4, 10.0, and acetone suspensions still contained the detrimental pyrochlore phase after heating at 900°C. The properties of the ceramics prepared from the pH 12.5 suspension are superior in comparison with the other samples.

In2O3–ZnO two-dimensional (2D) structures were processed by ink-jet printing and heating at 150°C and 450°C with the aim for implementation in transparent electronics. The In–Zn-solution precursor, based on In-alkoxide and Zn-acetate in 2-methoxyethanol, was originally designed for chemical solution deposition of thin films. To adapt it for piezoelectric ink-jet printing, the viscosity and surface tension were adjusted by the addition of a more viscous 1,3-propanediol. The optimum values were obtained for the ink consisting of 55 vol% of 1,3-propanediol. The printing parameters including the temperatures of the cartridge and the substrate, and the drop spacing were adjusted to allow patterning with a 40 μm resolution on SiOx/Si and glass substrates. The ink-jet-printed 2D structures heated at 150°C were amorphous and according to infrared spectroscopy organics-free, and upon heating at 450°C they crystallized without any preferential orientation, similarly as the spin-coated thin films, which were studied as a reference.

This paper describes an optimized analytical procedure for determining the composition of alkaline niobate-based lead-free piezoceramics by energy-dispersive X-ray spectroscopy (EDXS) in a transmission electron microscope (TEM). To discriminate the material-specific composition from the artifacts introduced during the EDXS/TEM analyses, the effects of radiation damage and the absorption of the characteristic X-ray lines were studied in detail. The optimized, quantitative EDXS analysis was tested on sodium potassium niobate with the nominal composition K0.5Na0.5NbO3 (KNN) by applying KNbO3 and NaNbO3 as standards. The results obtained indicate that KNbO3 is more radiation sensitive than NaNbO3. A similar degradation was confirmed in KNN, where the loss of potassium was higher than that of sodium. In addition, the degradation of the KNN was associated with a severe oxygen loss and the reduction of niobium. To achieve highly reliable, quantitative analyses and to preserve good counting statistics, the optimum conditions for the EDXS/TEM analyses were found at an electron dose rate of 0.4 pA/nm2 and an acquisition time of around 200 s in the specimen thickness range between 30 and 200 nm.

Processing of dense potassium tantalate ceramics is a challenging task. In our study, KTaO 3 powder was prepared by heating the mechanochemically activated K 2 CO 3 ―Ta 2 O 5 powder mixture at 800°C for 4 h. Another heating at 800°C was needed to improve the structural homogeneity of the powder. Sintering in air and oxygen atmospheres at 1325°C for 1 h resulted in the ceramics with relative densities around 85% and inclusions of the K 6 Ta 10.8 O 30 secondary phase. Phase-pure KTa0 3 ceramics with relative densities of 98% and 95% were obtained by hot-pressing the single- and the double-calcined powder compacts, respectively, at 1250°C for 2 h. The dielectric permittivity of the hot-pressed ceramic, prepared from the double-calcined powder, measured at 5 K and 1 kHz is 4080, which is almost twice the value obtained for the ceramic, prepared from the single-calcined powder, i.e. 2450, and is comparable with the value reported for the single crystals.

The article describes the approaches for a reliable, quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds. The combination of scanning electron microscopy (SEM) and transmission electron microcopy (TEM) with electron-probe analytical techniques, such as energy-dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDS) and electron-energy-loss spectroscopy (EELS) makes it possible to determine the true chemical composition, from precursor powders to synthesized ceramics or single crystals. The microscale (SEM) and nanoscale (TEM) analytical methods also give an insight into the local variations of the chemical composition.

In CaCu3Ti4O12 (CCTO), the ceramic material with the highest dielectric permittivity ever reported in a broad frequency and temperature range, the origin of such high permittivity has been attributed to ‘electrical’ heterogeneities in the microstructure. Dielectric investigations of CCTO ceramic thin films, performed in a broad temperature and frequency range, and the analysis in terms of the equivalent circle reveal that (i) each of the two constituents, insulating grain boundaries and semiconducting bulk grains, individually determines the dielectric behaviour of CCTO and (ii) manipulating the conditions under which CCTO ceramic thin films are prepared enables control of their dielectric properties.

We have made an effort to obtain a reliable quantitative composition of KTaO3, which belongs to the group of incipient ferroelectrics. A combination of two analytical spectroscopic methods of transmission electron microscopy was employed for the nanoscale analysis: energy-dispersive X-ray and electron energy-loss spectroscopy. Because of the volatile nature of alkali-based compounds, special attention was paid to optimization of acquisition parameters. The latter were tested on KTaO3 single-crystal specimen by applying various electron doses and monitoring the K/Ta ratio. The case study was based on the analysis of calcined KTaO3 powder prepared from a stoichiometric mixture of K2CO3 and Ta2O5, and KTaO3 ceramic prepared from the latter powder by hot pressing. At nanoscale, the particles of microscopically homogeneous powder appeared to have a slight excess of K relative to the nominal composition. Additionally, 5–20 nm sized nanoparticles, possessing both K- and Ta-rich compositions, were found to be attached to the cubic-shaped powder particles. Hot-pressed KTaO3 ceramic revealed exaggerated grain growth with compositional deviations of up to 5% within large grains as well as in matrix grains composition. The majority of analyzed matrix grains, however, showed a slight excess of Ta relative to the nominal composition.

This work aimed to describe the sol-gel synthesis and preparation of a near-morphotropic phase boundary lead-magnesium-niobium titanate (PMNT) material system, and to investigate the influences of room-temperature-UV-irradiation and rapid thermal annealing (RTA) processes on the properties of its thin films. It was postulated that the use of UV-irradiation prior to thermal processing could play a role in the generation of a structural difference that would manifest itself via the formation of a higher film thickness, which was more pronounced at higher RTA temperatures The PMNT thin film system described here (particularly those annealed at higher temperatures) appeared to be potentially suitable for ultrahigh-value-capacitor applications; the unexposed film annealed at 750 °C exhibited the highest high k value (1425) with a strongly pronounced perovskite phase (97%).

We have investigated the processing of 0.65Pb(Mg 1/3 Nb 2/3 )O 3 –0.35PbTiO 3 (denoted PMN–PT) thick films using an electrophoretic deposition process (denoted EPD), with the PMN–PT particles suspended in an ethanol-based suspension. The zeta-potential and the viscosity were measured to identify the conditions for the preparation of a stable suspension suitable for the EPD. The applied voltage, the deposition time, the chemical composition of the suspension and the concentration of the powder were investigated in order to obtain a high-quality PMN–PT deposit with a target thickness of about 50 μm. The PMN–PT thick films prepared from stoichiometric and PbO-excess suspensions by sintering at 950 and 1100 °C were examined by X-ray powder-diffraction analysis and scanning electron microscopy. The highest functional response was obtained for a homogeneous, dense, crack-free PMN–PT thick film prepared from a PMN–PT suspension with excess PbO. The film was deposited at a constant voltage of 10 V and for a time of 120 s, followed by sintering at 1100 °C in a PbO-rich atmosphere. The film's properties were as follows: a dielectric permittivity ɛ of 20,250 at a T m of 172 °C, a remanent polarization of 17 μC/cm 2 and a coercive field of 5 kV/cm.

In this review, the crystal structure and the synthesis of the sodium potassium niobate ( K 0.5 Na 0.5 NbO 3) as a promising candidate for lead-free piezoelectrics are addressed. The sintering and the microstructure as prerequisites for obtaining ceramics with reliable and sufficiently high piezoelectric properties for selected applications are discussed.

Abstract Thermal decompositions of the precursors for chemical solution deposition of 0·7 Pb(Mg1/3Nb2/3)O3-0·3 PbTiO3 (0·7PMN-0·3PT) thin films were studied. The precursors were prepared from lead acetate or acetylacetone modified lead acetate by diol based route and dried at 100°C. Thermal decompositions of the PT, PMN and PMN-PT precursors in air occur stepwise. Between room temperature and ∼200°C, the weight loss of a few per cent is due to the evaporation of residual solvents. Organic groups decompose in the ranges 200-400°C and 400-650°C. The thermal decompositions are affected by the choice of the Pb compound and chemical composition of the sample.

We studied the mechanochemical synthesis of KNbO3, starting from a powder mixture of K2CO3 and Nb2O5. The milling experiments were designed with different ball-impact energies in order to investigate the mechanochemical reactions. X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, Raman spectroscopy and transmission electron microscopy were used to characterize the samples. Based on the results, we propose a mechanism for the mechanochemical reaction between K2CO3 and Nb2O5. The first stage of the reaction is characterized by the formation of an amorphous carbonato complex, which decomposes after prolonged milling at higher ball-impact energy giving rise to the crystallization of KNbO3 and other niobate phases with a molar ratio K/Nb

KTa 0.6 Nb 0.4 O 3 thin films on polycrystalline alumina were prepared by Chemical Solution Deposition from potassium acetate and transition metal alkoxides in 2-methoxyethanol. Influence of the reflux time on the phase composition, microstructure, and dielectric properties of the films was studied. Films, prepared from the 1 h-refluxed solutions and heated at 900°C have dielectric permittivity value of 860, dielectric losses value of 0.01 and tunability (C 0V / C 30V ) value of 1.9. The corresponding values for the films, prepared from the 24 h-refluxed solutions, are 1690, 0.04, and 2.6, respectively.

In this work we investigated the chemical composition and structure of (K0.5Na0.5)NbO3 (KNN) single crystals grown by the solid state crystal growth method. The optical, scanning, and transmission electron microscopies were employed for the analysis of the chemical homogeneity and domain structure of the KNN crystal. No compositional inhomogeneities within experimental error were encountered in the KNN single crystals. The domain structure of the KNN single crystal, with a monoclinic unit cell, is composed of large 90° domains of up to 100 μm width, which further consist of smaller 180° domains with widths from 50 to 300 nm.

We have studied the formation of lead–magnesium–niobate Pb(Mg1/3Nb2/3)O3 perovskite powder produced by high-energy milling of the constituent oxides. By applying a low ball-impact energy and a low ball-impact frequency we were able to identify the reaction sequences. The crystal structure and the amount of crystalline and amorphous phases in the powder were determined using a Rietveld refinement. The morphology, structure and chemical composition of the powder were investigated by transmission electron microscopy. The surface composition, possible contamination and the chemical states of the elements were analyzed by X-ray photoelectron spectroscopy. In the early stage of milling the constituent oxides comminute, refine to nanosize dimensions and become amorphous. In the second step the Pb(Mg1/3Nb2/3)O3 nucleates from the amorphous regions where the stoichiometry corresponds to the perovskite. The perovskite phase nucleates and subsequently grows over the course of the milling. Simultaneously, the pyrochlore phase nucleates from the Pb- and Nb-rich regions; however, its nucleation and recrystallization stop after a certain milling time. The powder mixture consists of nanosized Pb(Mg1/3Nb2/3)O3 particles and an amorphous phase when milled for 94 h. No traces of contamination from the milling media were detected.

We have studied the processing of lead-zirconate-titanate PbZr0.53Ti0.47O3 (denoted PZT) based thick films using an electrophoretic deposition (EPD) process in order to obtain the active film with desired thickness and porosity at low the sintering temperature. The colloidal suspensions were prepared by mixing the ceramic powder in ethanol with the controlled addition of a polyelectrolyte salt and an organic base. In order to optimise the deposition process, the stability of the PZT and Pb5Ge3O11 (denoted PGO) particles in ethanol-based suspensions was studied. The electrophoretic deposition of PZT-PGO was performed from a mixture of optimal PZT and PGO suspensions in an appropriate molar ratio. PZT and PGO acting as a sintering aid were deposited on an Al2O3/Au substrate at a constant applied current and sintered at 850 oC. The thickness of the deposit was controlled by the deposition time and the applied current. PZT-PGO thick films deposited at 1.2 mA for 60 seconds and sintered at 850oC for 8 hours exhibited a room-temperature dielectric permittivity of 1050, dielectric losses of 0.038, a remanent polarisation Pr of 29 C/cm2, a coercive field Ec of 21 kV/cm and a d33 of 97pC/N.

The rheological behavior and tape-casting performance of ethanol-based Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) slurries is studied. A nanocrystalline powder obtained by mechanochemical activation was used. Suspensions were prepared up to solid contents of 32 vol%, significantly higher than those usually reported for nonaqueous systems. The feasibility of replacing toxic solvents commonly used for tape casting of functional ferroelectric materials, often toluene, with ethanol is demonstrated. The density, phases and microstructure of the green tapes and sintered ceramics are presented. Cube-shaped templates were successfully aligned during the tape casting for the processing of 〈001〉-textured PMN–PT ceramics by templated grain growth. An effect of the lamination of tape stacks on the template orientation is described.

TiO2, TiO2−x and Ti3O5 thick-film structures on corundum Al2O3 substrates were prepared using screen-printing technology. The screen-printed deposits were sintered up to 1500 °C in oxidising and reducing atmospheres to vary the Ti4+/Ti3+ ratio and consequently water contact angle. The structure of the thick films was studied with an X-ray powder diffractometer (XRD). The microstructural characteristics and the chemical composition were checked with a scanning electron microscope, equipped with an energy-dispersive spectrometer (EDS). The Ti–O films, up to 55 μm thick, exhibited excellent adhesion to the substrate and had uniform grain- and pore-size distributions. Ti3O5 and Al2O3 were found to be compatible phases up to 1500 °C in a reducing atmosphere. However, rutile-type TiO2 and Al2O3 are not compatible compounds at temperatures up to 1400 °C, in either oxidising or reducing atmospheres. TiO2 and TiO2−x form two types of reaction products with Al2O3. These reaction products were found to have various Ti/Al ratios.

All-ceramic lead-free percolative composite, comprising RuO 2 with high electrical conductivity denoted as the conductive phase and ferroelectric (K, Na)NbO 3 ceramics, was developed. Structural analysis revealed a uniform distribution of conductive ceramic grains within the ceramic matrix. Consequently, the dielectric response in the (K, Na)NbO 3 –RuO 2 composite follows the predictions of the percolation theory. Thus, close to the percolation point exceptionally high values of the dielectric constant were obtained—values as high as 20,000 were detected at room temperature at 1 kHz. Fit of the data, obtained for samples of different compositions, revealed critical exponent and percolation point, which reasonably agree with the theoretically predicted values.

This paper presents the crystal structure and the phase transitions of K x Na 1− x NbO 3 (0.4 ≤ x ≤ 0.6). X-ray diffraction measurements were used to follow the change of the unit-cell parameters and the symmetry in the temperature range 100–800 K. At room temperature all the compositions exhibited a monoclinic metric of the unit cell with a small monoclinic distortion (90.32° ≤ β ≤ 90.34°). No major change of symmetry was evidenced in the investigated compositional range, which should be characteristic of the morphotropic phase-boundary region. With increasing temperature, the samples underwent first-order monoclinic–tetragonal and tetragonal–cubic transitions. Only the potassium-rich phases were rhombohedral at 100 K.

This paper specifically examines control of the residual stress in thin films by design of the stacking structure. For this study, we prepared highly a-, c- oriented PZT(30/70) (: PZT30) thin films using chemical solution deposition (CSD). A PZT30 thin film was deposited on LaNiO3 (LNO)/Pt/Ti/SiO2/Si and LNO/SiO2/Si with different LNO layer thickness to control the thermal stress. An LNO layer was also prepared using CSD on a Pt/Ti/SiO2/Si substrate and SiO2/Si substrate. The residual stresses in the PZT30 thin films were estimated using Raman analysis. Furthermore, the dielectric property of samples was measured using an impedance analyzer. Effects of the residual stress on the dielectric behavior were demonstrated through experimentation.

In the present work the LaCoO3 formation from gel precursors obtained by water-based sol-gel method with citric acid was studied. As precursors La and Co nitrates were used. The obtained gels were analyzed by TG/ DTA and TG/EGA. The decomposition of the gels takes place in two main steps with the evolution of the same volatile compounds (H2O, CO2 and NO2) leading to the conclusion that two types of bonding of the components in the gels occurred. The decomposition of the gels takes place up to 400?C. The gels thermally treated at 600?C lead to single pure perovskite rhombohedral phase of lanthanum cobalt oxide (LaCoO3). Some electrical properties of LaCoO3 measured in 'operando' conditions, i.e. in gas flow, at atmospheric pressure (by using the differential step technique DST) are presented and discussed.

We have investigated the processing of 0.65Pb(Mg 1/3 Nb 2/3 )O 3 –0.35PbTiO 3 (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a T m of 174 °C, a permittivity at the T m of 21,000 and a d 33 of 140 pC/N.