Multicomponent ceramics based on PbMg1/3Nb2/3O3-PbTiO3 system were studied using X-ray diffraction at high electric fields. It was shown that electric field induced phase transition from initial pseudocubic phase to tetragonal one occurs at E > 5 kV/cm. Analysis of the intensities of the 200 X-ray peak components reveals the parameters of the tetragonal unit cell (c = 4.036 & ANGS; and a = 4.021 & ANGS;) and the degree of preferential domain orientation (& AP; 35%) at E = 12 kV/cm. The results of X-ray diffraction studies are in a good agreement with the field-induced behavior of the macroscopic responses: strain, polarization, and dielectric permittivity.

Ceramic samples of BiFeO3-based perovskite solid solutions with the highly ordered complex perovskites [Formula: see text][Formula: see text]O3(PFS) and [Formula: see text][Formula: see text]O3 (SFS) were obtained using high-pressure synthesis at 4–6 GPa. Mössbauer studies revealed that BiFeO3-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO3-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature [Formula: see text] for BiFeO3-SFS compositions is close to the [Formula: see text] dependence for BiFeO3solid solution with disordered perovskite [Formula: see text][Formula: see text]O3(PFN). In contrast to this [Formula: see text] dependence for BiFeO3-PFS compositions nicely follows the theoretical [Formula: see text] dependence calculated for the case of the ordered distribution of Fe[Formula: see text] and non-magnetic Sb[Formula: see text] ions in the lattice (chemical ordering).

0.5BiFeO(3)-0.5Pb(1-x)Sr(x)TiO(3) (0 <= x <= 1) solid solution compositions were synthesized using solid phase reactions route from high-purity oxides. Mossbauer studies showed that for 0.5BiFeO(3)-0.5PbTiO(3) (x = 0) the magnetic phase transition temperature T (M) value was about 130 K. Substitution of Sr for Pb led to a dramatic decrease in T (M), though the Fe content did not change with x and for 0.5BiFeO(3)-0.5SrTiO(3) (x = 1) T (M) was only approximate to 20 K. This dramatic difference in T (M) values seems to be due to additional contribution of the magnetic superexchange between Fe3+ ions via the empty 6p states of Bi3+ and Pb2+ ions to the overall superexchange.

Abstract x,T-phase diagram of the solid solution of multiferroic PbFe1/2Ta1/2O3 with ferroelectric PbTiO3 for the 0 ≤ x ≤ 0.3 compositional range was plotted for the first time using the data of dielectric, piezoelectric, and Mössbauer studies.

— Barium strontium niobate films ~300 nm in thickness have been grown on MgO(001) substrates by rf sputtering of a ceramic target with the stoichiometric composition Sr 0.5 Ba 0.5 Nb 2 O 6 (SBN50) in an oxygen atmosphere. Composition–depth profiles across the films have been measured using secondary ion mass spectrometry, and we have determined their phase composition, structure, and c cell parameter in the temperature range 20–500°C. The results demonstrate that the SBN50 films are heteroepitaxial and have two crystallographic orientations with an angle of ~36.8° between them and identical tetragonal cell parameters ( а = 12.438 Å and с = 3.955 Å). Their chemical composition does not vary in the thickness direction and corresponds to the composition of the ceramic target. The SBN50 films have a higher temperature of the ferroelectric-to-paraelectric phase transition than do SBN50 single crystals and polycrystalline films, and their thermal expansion coefficient changes sign near 100°C.

0.5[Formula: see text]FeO3–0.5NaNbO3 ([Formula: see text], La) solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides. Mössbauer studies have shown that while for 0.5BiFeO3–0.5NaNbO3 the magnetic phase transition temperature [Formula: see text] value is about 150[Formula: see text]K, for 0.5LaFeO3–0.5NaNbO3, it is only [Formula: see text][Formula: see text]K. This dramatic difference in [Formula: see text] values seems to be due to additional contribution of the magnetic superexchange between [Formula: see text] ions via the empty 6p-states of [Formula: see text] ions to the overall superexchange.

Valence states of iron and tantalum ions in eight ceramic compounds with a perovskite structure A(x)B(y)Ta(z)O(3+sigma) (A = Pb, Ba, Sr, Ca; B = Fe, Sc) were studied, including the compounds A(x)Fe(y)Ta(z)O(3+sigma), (A = Ba, Sr, Ca) annealed in a reducing atmosphere of CO. In a number of samples, the presence of Fe2+ ions was detected along with Fe3+. Relative fractions of the Fe2+ and Fe3+ ions were obtained by a full-profile fitting of the Fe2p X-ray photoelectron spectra (XPS) by superposition of experimental spectra of Fe2+ and Fe3+ ions, and by the Mossbauer spectroscopy method. The presence of Ta4+ ions along with Ta4+ ions was detected. The samples subjected to high-temperature annealing in the atmosphere of CO contain only Ta4+ ions. A modification of a standard methodology of the XPS determination of elemental compositions is proposed for the cases when the O1s-spectra have high-energy "tails"; it is based on ensuring the electrical neutrality of the samples. Changes in the elemental and ionic composition of the samples reflect the effect of the annealing of samples in a reducing atmosphere of CO.

Abstract Multiferroic Pb(Fe0.5Nb0.5)1-xCexO3 (x = 0.025, 0.05, 0.075, 0.10) ceramic compositions were prepared by solid state synthesis and usual sintering. XRD studies have shown a formation of the perovskite structure in all the compositions studied. However a small amount of pyrochlore phase was detected in Ce-doped compositions with x ≥ 0.075. Scanning electron microscopy studies and elemental analysis have shown that at the boundaries of the large grains of nearly pure PbFe0.5Nb0.5O3 there exist a lot of small submicron grains enriched by Ce. Concentration dependencies of the unit-cell parameter and temperatures of ferroelectric and magnetic phase transitions also imply that solubility of Ce in PFN does not exceed ≈ 2 at.%.

Recently we have found out that high-energy mechanical activation during mechanochemical synthesis stimulates disordering of Yb3+ and Nb5+ cations in the PbYb1/2Nb1/2O3 (PYN) ceramics. However, one could expect a contamination of thus obtained ceramics by iron as the planetary mill AGO-2 with both jars and balls made of the stainless steel was used for mechanical activation. To elucidate the effect of iron doping on the compositional ordering of PYN, in the present work several (1 − x)PYN–xPbFe1/2Nb1/2O3 (PYN–xPFN) solid solution compositions have been fabricated by both the usual solid-state synthesis and by high-energy mechanochemical synthesis and their structure and properties were compared. Basing on these data the (x, T)-phase diagrams for the PYN – xPFN solid solutions fabricated by both methods were constructed. It was found out that the difference in the lattice parameters values and dielectric properties of ceramics fabricated by different methods are partially due to the formation of the (1–x)PYN–xPFN solid solutions with PFN content larger than nominal one and partially due to the effect of high-energy mechanical activation.

Temperature dependences of the dielectric permittivity ε of (1−x)PbFe0.5Nb0.5O3-x BaFe0.5Nb0.5O3 solid solution ceramics at 100 Hz–1 MHz have been studied in the 12–500 K temperature range. To lower the conductivity values and exclude the corresponding relaxations, 1 wt% of Li2CO3 was added to the starting mixture of oxides. It was found that Li-doping is effective in lowering the conductivity only for compositions with x ≤ 0.5. The permittivity–temperature dependences of the (1−x)PbFe0.5Nb0.5O3–xBaFe0.5Nb0.5O3 compositions were found to change, as x grows, from relatively sharp frequency-independent maxima typical of usual ferroelectrics to the diffused and frequency-dependent maxima typical of relaxors and then to the saturated at low temperatures and frequency-independent ε(T) curves typical of incipient ferroelectrics and at last, to the step-like frequency-dependent ε(T) curves known for the dielectrics with Maxwell–Wagner-type polarization. The ε value of BaFe0.5Nb0.5O3 at 20 K measured at 1 MHz does not exceed 30. The character of the evolution of dielectric properties in the (1−x)PbFe0.5Nb0.5O3–x BaFe0.5Nb0.5O3 system and low ε value of BaFe0.5Nb0.5O3 implies that BaFe0.5Nb0.5O3 is a paraelectric rather than ferroelectric relaxor.

Recently we found out that compositional ordering degree s of Yb3+ and Nb5+ ions in PbYb1/2Nb1/2O3 (PYN) ceramics can be varied by means of high-energy mechanical activation. In the present work dielectric and X-ray diffraction studies of the three obtained PYN ceramic samples with differing s values have been carried out in a wide temperature range. The highly disordered (s approximate to 0) sample appeared to be cubic in the 20-350 degrees C range and exhibited a diffused and frequency-dependent permittivity maximum at T-m approximate to 80 degrees C. Samples with s = 0.69 and 0.82 were orthorhombic at room temperature and exhibited non-diffused and frequency-independent permittivity maximum at T-m approximate to 170 and 250 degrees C respectively. However even in the most ordered PYN sample (s approximate to 0.82) cubic paraelectric and orthorhombic antiferroelectric phases coexist in the 190-300 degrees C temperature range.

Recently we have found out that high-energy mechanical activationmechanical activation during mechanochemical synthesis stimulates disordering of Yb3+ and Nb5+ cations in the PbYb1/2Nb1/2O3 (PYN)PbYbNbO (PYN) ceramics. However, one could expect a contamination of thus obtained ceramics by iron as the planetary mill AGO-2 with both jars and balls made of the stainless steel was used for mechanical activationmechanical activation. To elucidate the effect of iron doping on the compositional orderingcompositional ordering of PYNPYN, in the present work several (1 − x)PYN–xPbFe1/2Nb1/2O3 (PYN–xPFN)(1 − )PYN–PbFeNbO (PYN–xPFN) solid solution compositions have been fabricated by both the usual solid-state synthesis and by high-energy mechanochemical synthesis and their structure and properties were compared. Basing on these data the (x, T)-phase diagrams for the PYN – xPFNPYN–xPFN solid solutions fabricated by both methods were constructed. It was found out that the difference in the lattice parameters values and dielectricdielectric propertiesdielectric properties of ceramics fabricated by different methods are partially due to the formation of the (1–x)PYN–xPFN(1 − )PYN–PFN solid solutions with PFNPFN content larger than nominal one and partially due to the effect of high-energy mechanical activationmechanical activation.

It was found out that compositional ordering degree S of Yb3+ and Nb5+ ions in PbYb1/2Nb1/2O3 ceramics and correspondingly both the temperature and diffusion of antiferroelectric phase transition can be varied within a wide range by means of high-energy mechanical activation. In particular, for the first time disordered PbYb1/2Nb1/2O3 ceramics exhibiting relaxor-like dielectric properties was fabricated without the use of any additives. For the most ordered PbYb1/2Nb1/2O3 samples (S ≈ 0.82), the coexistence of cubic paraelectric and orthorhombic antiferroelectric phases in a temperature range 190–300 °C was revealed.

A number of ferroelectric thin films with various barium concentration and two sets of superlattices with different composition and number of constituent layers were investigated using X-ray diffraction. Out-of-plane unit cell parameters, values of microstrains, and sizes of coherent scattering regions were determined. Modulation period for superlattices was also calculated. We discuss the structural features of the samples.

Ceramic PbFe0.5−x Cr x Nb0.5O3 (x = 0.025, 0.05, 0.10, 0.15) perovskite solid solutions are synthesized using a solid-state reaction method. The samples of solid solutions are studied using the methods of X-ray diffraction, dielectric, Mössbauer and X-ray photoelectron spectroscopy, electron microscopy, and X-ray microanalysis. XRD studies have shown that the content of the parasitic pyrochlore phase increases dramatically with x, approaching 50% for x = 0.15. The averaged lattice parameter and the temperature of ferroelectric phase transition decrease monotonically with x. Concentration dependence of the magnetic phase transition temperature for PbFe0.5−x Cr x Nb0.5O3 is very similar to that in the Pb(Fe0.5Nb0.5)1−x M x O3 (M = Ti, Zr, Sn) solid solutions implying the lack of magnetic exchange between Fe3+ and Cr3+ ions. Bulk and surface elemental compositions are found to differ from each other and from nominal composition. XPS studies revealed that the PbFe0.5−x Cr x Nb0.5O3 (x = 0.05, 0.10) samples contain Cr3+, Cr4+, Cr5+, and Cr6+ ions. It is assumed that the presence of Cr5 + and Cr6+ ions is due to the formation of a small amount of non-perovskite phases, e.g., Pb n 2+ Cr6+O3+n and Fe3+Cr5+O4. This assumption is supported by the presence of weak reflections of the Pb2 2+Cr6+O5 phase in the XRD pattern of the composition with x = 0.15.

Solid solution Sr 0.5 Ba 0.5 Nb 2 O 6 films have been synthesized on a (111)Pt/(001)Si substrate by rf deposition in an oxygen atmosphere. The depolarized Raman spectra, the structure, and the dielectric characteristics of the films have been studied over a wide temperature range. It is found that the films were singlephase, had the tetragonal tungsten bronze structure, and had a pronounced axial texture with axis 001 directed perpendicular to the substrate surface. It is shown that the film material undergoes a diffuse phase transition to the state of a relaxor ferroelectric in the temperature range 300–425 K. Possible reasons of the regularities observed are discussed.

Neel temperature of Pb(Fe1/2Nb1/2)O-3 ceramics sintered at 1120 degrees C and quenched to room temperature was revealed to be 25K higher than that of the same ceramics slowly cooled at a rate of 50K/h. A small singlet component, typical for compositionally ordered perovskites, is present in the room-temperature Mossbauer spectrum of the slowly cooled sample. It proves that the quenched sample is more compositionally disordered than the slowly-cooled one. Substantially higher room-temperature resistivity values and positive temperature coefficient of resistivity of the slowly cooled sample are attributed to the formation of the grain-boundary potential barriers due to oxidation during slow cooling.

Методом высокочастотного напыления в атмосфере кислорода получены пленки твердого раствора Sr0.5Ba0.5Nb2O6 на подложке (111)Pt/(001)Si. Изучены их деполяризованные спектры комбинационного рассеяния света, структура и диэлектрические характеристики в широком диапазоне температур. Установлено, что пленки однофазны, обладают структурой тетрагональной вольфрамовой бронзы, имеют ярко выраженную аксиальную текстуру с осью 001, направленной перпендикулярно поверхности подложки. Показано, что в интервале температур 300-425 K в материале пленки происходит размытый фазовый переход в состояние сегнетоэлектрика-релаксора. Обсуждаются возможные причины выявленных закономерностей. Работа выполнена в рамках реализации государственного задания на 2016 г N 007-01114-16 ПР (проект N 0256-2014-0002) и гранта РФФИ N 16-32-60095 мол\_а\_дк. DOI: 10.21883/FTT.2017.05.44376.382