X-ray diffraction and dielectric studies were performed on synthesized ceramic samples of the section (1–x) (0.8PbMg[Formula: see text]Nb[Formula: see text]O[Formula: see text]BiScO 3 )⋅ x(0.8PbTiO[Formula: see text]BiScO 3 ) with [Formula: see text]–1 of the ternary BiScO 3 –PbTiO 3 –PbMg[Formula: see text]Nb[Formula: see text]O 3 (BS–PT–PMN) system, including the temperature dependence of thermally stimulated depolarization currents (TSDC). It was found that the samples are solid solutions with a perovskite structure, which have cubic symmetry in the range of x = 0–0.587 and tetragonal symmetry in the range of x = 0.680–1. In the intermediate composition range of x = 0.587–0.680 (morphotropic region — MR), the samples consist of a mixture of solid solutions of different symmetries. Data on the change in dielectric properties and TSDC(T) dependencies of solid solutions with a change in their composition were obtained. It was found that samples of compositions x =0–0.625 and 0.6875–1 exhibit relaxor-ferroelectric and conventional ferroelectric properties, respectively, while samples of compositions x = 0.625–0.6875 combine ferroelectric and relaxor-ferroelectric properties.

This article studies the influence of solid-phase (type 1 samples) and melt-quenching (type 2 samples) technological modes of obtaining Na3Fe2(PO4)3 polycrystals on their structures and ion-conducting properties. α-Na3Fe2(PO4)3 polycrystals of the 1st type are formed predominantly under an isothermal firing regime, and the synthesis of the 2nd type is carried out under sharp temperature gradient conditions, contributing to the formation of glassy precursors possessing a reactive and deformed structure, in which the crystallization of crystallites occurs faster than in precursors obtained under isothermal firing. The elemental composition of α-Na3Fe2(PO4)3 type 2 polycrystals is maintained within the normal range despite the sharp non-equilibrium thermodynamic conditions of synthesis. The microstructure of the type 1 Na3Fe2(PO4)3 polycrystals is dominated by chaotically arranged crystallites of medium (7–10 μm) and large (15–35 μm) sizes, while the polycrystals of type 2 are characterized by the preferential formation of small (3–4 μm) and medium (7–10 μm) crystallites, causing uniaxial deformations in their structure, which contribute to a partial increase in their symmetry. The advantage of type 2 polycrystals is that they have higher density and conductivity and are synthesized faster than type 1 samples by a factor of 4. The article also considers the issues of crystallization in a solid-phase precursor from the classical point of view, i.e., the process of the formation of small solid-phase nuclei in the metastable phase and their growth to large particles due to association with small crystallites using phase transitions. Possible variants and models of crystallite growth in Na3Fe2(PO4)3 polycrystals, as well as distinctive features of crystallization between two types of samples, are discussed.

In this work, the features of the structure-conductivity relationship in polar (α) and ion-conducting (β and γ) phases of Na3Fe2(PO4)3 polycrystals obtained by the melt-quenching method have been investigated. Na3Fe2(PO4)3 polycrystals are synthesized by isothermal firing of glassy precursors (after grinding and pressing). The glassy precursors were prepared by melting a pre-calcined (350 C) mixture of initial reagents under the influence of thermal and infrared radiation energy and rapid cooling of the melt (or quenching). It was found that the deformations of the structure of polycrystals α-Na3Fe2(PO4)3 during synthesis by melt-quenching lead to an increase in the conductivity in polar (α) and ion-conducting (β and γ) phases because they contribute to the reduction of structural distortions of the samples. Polycrystals Na3Fe2(PO4)3 obtained by the melt-hardening method have high-quality crystallites, high density, and conductivity, and their synthesis is faster than samples obtained by other methods. The established advantages of synthesized polycrystals of α-Na3Fe2(PO4)3 are probably connected with deformations of structure and chemical activity of glassy precursors caused by nonequilibrium thermodynamic conditions of synthesis. For the first time, it was possible to detect domain structures in polycrystals of α-Na3Fe2(PO4)3 obtained by the melt-quenching method, which confirms the polarity of the α-phase, the appearance of which is associated with the ordered displacement of the cationic sublattice relative to the anionic sublattice under the influence of monoclinic distortion of the crystal framework.

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO3·0.45PbTiO3·0.35PbMg1/3Nb2/3O3 (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d33~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times.

In the paper the results of the study on the synthesis of high-temperature superconducting ceramics of nomi- nal composition Bi1.6Pb0.4Sr2Ca2Cu3Oy by various methods were presented based on amorphous phases using glass-ceramic technology and solid-phase method. For comparison, amorphous phases were obtained in two ways. In the first case, a heating furnace of a special design was developed to obtain an amorphous phase, which provides melting without using a crucible. The heating of the initial samples for melting is carried out due to the combined effect of the convection heat flux and the radiation of heating elements, which consists of the IR region of the spectrum at a melting temperature in the spectral range of 1300–1350 nm. In the se- cond case, melting is carried out under the influence of broadband optical radiation, including UV, visible and IR spectral regions. The production of glassy precursors is carried out by draining the melt onto a quenching device in the form of a propeller made of stainless steel. Studies of the formation rate of the superconducting high-temperature phase Bi-2223 were carried out in the same temperature conditions at 848–850 °C with in- termediate grinding every 24 hours and the study of the phase composition by X-ray diffraction method. Studies showed that the glass phase-based method ensures the completeness of the formation of the high- temperature phase Bi-2223 and the rate of its formation is significantly higher than by the solid-phase method (2.5–3 times). Studies of the critical density of the transport current have shown that the current value is 7.05×103 mA/cm2, (measured by the criterion of 1 µV/cm), which is significantly higher compared to other methods.

Ceramic samples with compositions along the (1 – 2 x )BiScO 3 ·(2 – y ) x PbTiO 3 ∙ yx PbMg 1/3 Nb 2/3 O 3 ( y = 1.2, 1.0, 0.9, 0.5) sections in the BiScO 3 –PbTiO 3 –PbMg 1/3 Nb 2/3 O 3 (BS–PT–PMN) system have been characterized by X-ray diffraction and dielectric, piezoelectric, and thermally stimulated depolarization current measurements. The materials with 1 – x ≲ 0.5 have been shown to consist of perovskite solid solutions. With increasing BS content, the symmetry of the solid solutions rises from tetragonal to cubic. In the intermediate composition region (morphotropic region (MR)), the samples consist of a mixture of solid solutions differing in symmetry. We have located the MR boundaries and examined the effect of composition on the dielectric and piezoelectric properties of the solid solutions.

This article investigates the structures and conductive properties of polycrystals of Na3Fe2(PO4)3 obtained by solid-state and melt synthesis methods using concentrated optical radiation. It has been established that in the melt synthesis method, the material is synthesized under significantly non-equilibrium thermodynamic conditions, leading to the creation of deformations in the sample, which contribute to the enhancement of ionic conductivity. Additionally, the synthesis duration is reduced by half. Through a comparative assessment of the structural parameters and conductive properties of these materials, it is demonstrated that polycrystals obtained by the melt method exhibit better texture and higher ionic conductivity. The occurrence of deformations during the synthesis of α-Na3Fe2(PO4)3 under high temperature-gradient conditions indicates the elasticity of the crystalline framework {[Fe2(PO4)]3−}3∞. It is concluded that the non-equilibrium thermodynamic conditions of α-Na3Fe2(PO4)3 synthesis promote the formation of deformations in the crystalline structure of polycrystals, leading to a partial increase in symmetry and ionic conductivity.

Ceramic samples with compositions along the (1 – 2x)BiScO3·(2 – y)xPbTiO3∙yxPbMg1/3Nb2/3O3 (y = 1.2, 1.0, 0.9, 0.5) sections in the BiScO3–PbTiO3–PbMg1/3Nb2/3O3 (BS–PT–PMN) system have been characterized by X-ray diffraction and dielectric, piezoelectric, and thermally stimulated depolarization current measurements. The materials with 1 – x ≲ 0.5 have been shown to consist of perovskite solid solutions. With increasing BS content, the symmetry of the solid solutions rises from tetragonal to cubic. In the intermediate composition region (morphotropic region (MR)), the samples consist of a mixture of solid solutions differing in symmetry. We have located the MR boundaries and examined the effect of composition on the dielectric and piezoelectric properties of the solid solutions.

The article presents the results of a study aimed at obtaining the formation of superconducting phases and the formation of a high texture of particles that affect the current-carrying characteristics in ceramics of the composition Bi1.6Pb0.4Sr2Ca3Cu4Oy and the study of their properties. For the synthesis of ceramics, precursors from the glass phase were used, which were obtained by melting the starting material under the influence of radiant flux (IR radiation) and quenching the melt in a facility rotating at a speed of 3000 rpm. Platinum wire was used as a substrate. During the heat treatment of samples in the temperature range of 845–850 °C and a holding time of 72 hours (with intermediate grinding every 24 hours), the superconducting high-temperaturephase Bi-2223 crystallized in the studied samples. Critical temperatures and resistances of superconducting samples were measured by the four-probe method by measuring the dependence of resistance on the temperature in the range from 300 K to 60 K.

"Мақалада ультракүлгін лазерлі сәулеленуді және спектрдің ультракүлгін, көрінетін және жақын инфрақызыл аймағын қамтитын оптикалық диапазонның кең спектрлік құрамының жоғары тығыздықты сәулеленуін қолдана отырып алынған балқымадан висмут негізіндегі жоғары температуралы өткізгіш қосылыстардың синтезі бойынша зерттеу нәтижелері келтірілген. Балқымадан алынған бастапқы прекурсор-материалдарының асқын өткізгіш фазалардың пайда болуына әсері және асқын өткізгіш қыштың шекті параметрлері зерттелді. Бастапқы прекурсор-материалдарын балқымадан алу жағдайларына байланысты материалдардағы оттегі бойынша стехиометриялық құрамның бұзылуы орын алатыны және бұл стехиометрия асқын өткізгіш фазалардың пайда болу кинетикасы мен динамикасына, асқын өткізгіш қыш қасиеттеріне әсер ететіні анықталды. Bi-2212 композициясының керамикалық үлгілері үшін төрт контактілі әдісті қолдана отырып асқын өткізгіштік күйге өту температурасын зерттеу арқылы өтудің басталуы (Тc) 80 К сәйкес келетіні анықталды. Ал Bi–2223 композиция үшін керамикалық үлгісі өтудің басталуы 112 К сәйкес келеді. Bi-2212 композициясының керамикасы үшін асқын өткізгіштік күйге өту ені 2 К, ал Bi-2223 керамика үшін өту ені шамамен 10 К. Кең ауысу үлгідегі қоспалардың болуымен және асқын өткізгіштің ақаулы құрылымымен байланысты болуы мүмкін. Кілтті сөздер: асқын өткізгіштік, температура, қыш, синтез, дифрактограмма, морфология, микроқұрылым. "

In this research, the structure parameters, conducting and dielectric properties of Na3Fe2(PO4)3 and Na2FePO4F polycrystals were studied obtained by solid-phase synthesis. The phase transition temperatures, conducting and dielectric parameters of Na3Fe2(PO4)3 and Na2FePO4F polycrystals were refined. A comparative evaluation of the conductive properties of Na3Fe2(PO4)3 and Na2FePO4F polycrystals is given in this article. The prospects of using of Na3Fe2(PO4)3 and Na2FePO4F are justified as electrode materials in sodium ion batteries.

AbstractProblems of the dipole ordering and ionic conductivity of Na_3Sc_2(PO_4)_3 polycrystal that has three polymorphic phases—α, β, and γ—are studied. The features of the α-Na_3Sc_2(PO_4)_3 crystal structure and the dipole ordering and relaxation polarization in the α and β phases are specified. The origin of the dipole ordering in the α phase and the partial dipole disordering in the β-Na_3Sc_2(PO_4)_3, as well as the high ionic conductivity in the β and γ phases of the Na_3Sc_2(PO_4)_3 polycrystal are associated with phase transformations α → β, β → γ that result in structural changes of the rhombohedral {[Sc_2(PO_4)_3]^3–}_3∞ crystalline framework. A model explaining the emergence of the dipole ordering and the ionic conductivity phenomena in Na_3Sc_2(PO_4) is proposed.

Problems of the dipole ordering and ionic conductivity of Na3Sc2(PO4)3 polycrystal that has three polymorphic phases—α, β, and γ—are studied. The features of the α-Na3Sc2(PO4)3 crystal structure and the dipole ordering and relaxation polarization in the α and β phases are specified. The origin of the dipole ordering in the α phase and the partial dipole disordering in the β-Na3Sc2(PO4)3, as well as the high ionic conductivity in the β and γ phases of the Na3Sc2(PO4)3 polycrystal are associated with phase transformations α → β, β → γ that result in structural changes of the rhombohedral {[Sc2(PO4)3]3–}3∞ crystalline framework. A model explaining the emergence of the dipole ordering and the ionic conductivity phenomena in Na3Sc2(PO4) is proposed.

Three-dimensional superionic conductors with framework structures of rhombohedral type are promising materials for use in solid electrolytes in Na-S batteries. The most effective representatives of this group of substances are the sodium-zirconium silicophosphate produced previously having the approximate composition Na/sub 3/Zr/sub 2/Si/sub 2/Po/sub 12/ (NASICON) and the compound Na/sub 3/ Sc/sub 2/ (PO/sub 4/)/sub 3/. This paper researches compounds and solid solutions having (M/sub 2/(EO/sub 4/)/sub 2/)P-/sub 300/ rhombohedral frameworks (M is a trivalent or quadrivalent cation, and E is P, Si, or Ge). The authors attempt to examine the existence conditions for phases similar in structure and properties to NASICON and to establish the effects of various forms of substitution in the framework on the structural and electrophysical characteristics. The entire discussion is based on previous crystallochemical analysis of the composition-structure-property relationships for compounds crystallizing in the rhombohedral structural type, as well as with the structure types of garnet and langbeinite and on a proposed model for phase transitions of ferroelectric-superionic type in Na-Sc phosphate.