Synthesis and Properties of BiFeO3–DyMnO3 Solid Solutions

(1 – x)BiFeO₃–xDyMnO₃ solid solutions with x= 0.03–0.30 are synthesized for the first time, and their dielectric and magnetic properties are studied. The solid solutions with x 0.08 have a rhombohedrally distorted perovskite structure, and those with x = 0.10–0.30 have an orthorhombically distorted structure. The 1-kHz electrical conductivity of the solid solutions exhibits semiconducting behavior and rises exponentially with temperature. The dielectric properties of the solid solutions are investigated in the microwave range (0.5–2.5 GHz) between room temperature and 250°C. The real part of their room-temperature dielectric permittivity reaches a maximum at x= 0.20, while the largest tan is observed at x = 0.03. The solid solutions with x= 0.03–0.08 exhibit high dielectric losses and are, therefore, candidate microwave absorbing materials. The magnetic and electrical ordering temperatures in the composition range studied exceed room temperature; that is, these solid solutions are new high-temperature seignettomagnetic materials.     

Properties of TlInSe2–TlNdSe2 Solid Solutions

TlIn_{1 – x} Nd _x Se₂(0 < x 0.1) solid solutions were characterized by x-ray diffraction and temperature-dependent electrical conductivity, Hall effect, thermoelectric power, and heat capacity measurements. With increasing Nd content, the lattice parameters of the solid solutions increase almost linearly, and their band gap decreases.     

Effect of Gamma Irradiation on the Piezoelectric Properties of K2Sr4Nb10O30–K6Li4Nb10O30 Solid Solutions

The effect of gamma irradiation on the dielectric ( ₃₃/₀, tan) and piezoelectric (d ₃₁, g ₃₁, K _p, Q _m) properties of ₂Sr₄Nb₁₀O₃₀–K₆Li₄Nb₁₀O₃₀ solid solutions (tetragonal tungsten bronze structure) was studied as a function of K₆Li₄Nb₁₀O₃₀ content. The results demonstrate that increasing the gamma dose to 9 × 10⁵ Gy reduces ₃₃/₀ and tan. With increasing Li⁺ content (filling of triangular channels), d ₃₁, g ₃₁, K _p, and Q _m increase. The results are interpreted in terms of the generation of stable defects and effective redistribution of the energy of gamma radiation over the ceramic sample.     

Phase Diagram and Luminescent Properties of CdTe–MnTe Solid Solutions

The T–x phase diagram of the CdTe–MnTe system is mapped out. The CdTe–MnTe join is shown to be nonpseudobinary. The system contains an extended series of CdTe-based solid solutions (0–71.4 mol % MnTe at 1070 K). At 1070 K, -MnTe dissolves up to 0.3 mol % CdTe. Data are presented on the composition dependences of lattice parameters for the solid solutions studied and the luminescent properties of Cd_{1 – x} Mn _x Te single crystals annealed in cadmium or tellurium vapor.     

Dielectric and Magnetic Properties of Pb(Fe1 /2Nb1 /2)O3–Pb(Fe2 /3W1 /3)O3Solid Solutions

Pb(Fe_1/2Nb_1/2)O₃–Pb(Fe_2/3W_1/3)O₃solid solutions were characterized by dielectric measurements at low frequencies and in the microwave range and magnetic measurements at high frequencies. The observed microwave dispersion was tentatively attributed to the domain mechanism of polarization. The obtained results suggest that the solid solutions studied are potential microwave-absorbing materials.     

Mössbauer Study of Tetragonal ZrO2–Y2O3–Fe2O3 Solid Solutions

Tetragonal Zr_0.886Y_0.057Fe_0.057O_{2 –} solid solutions prepared by calcining coprecipitated and successively precipitated hydroxide mixtures were studied by Mössbauer spectroscopy immediately after calcination and after long-term storage. The results indicate that the solid solutions prepared via coprecipitation and successive precipitation contain Fe³⁺ in two (octahedral coordination) and three (octahedral, fivefold, and tetrahedral coordinations) inequivalent sites, respectively. Partial Fe³⁺ substitution for Y³⁺ is shown to prevent or substantially slow down the low-temperature structural degradation of stabilized zirconia.     

Phase Transitions and Ferroelectric and Superionic Properties of K3Nb3B2O12–K3Nb3Si2O13 Single Crystals

Data are presented on K₃Nb₃O₆(B₂O₆)_1–x (Si₂O₇) _x solid solutions in the K₃Nb₃B₂O₁₂–K₃Nb₃Si₂O₁₃ system. The system is shown to contain two partial solid-solution series in the composition ranges 0 < x< 0.2 (KNB:Si) and 0.8 < x< 1 (KNS:B). KNB:Si crystals are grown from off-stoichiometric melts, and their polymorphism and physical properties are studied. Similar to K₃Nb₃B₂O₁₂, KNB:Si crystals exhibit a complex polymorphism and combine ferroelectric, ferroelastic, and superionic properties. Si substitution for B is shown to have a significant effect on the phase-transition temperatures and electrical properties of K₃Nb₃B₂O₁₂ crystals. The results obtained for K₃Nb₃Si₂O₁₃ crystals demonstrate that, in spite of their hexagonal habit, their room-temperature structure possesses orthorhombic or lower symmetry. The room-temperature dielectric permittivity ₃₃ of K₃Nb₃Si₂O₁₃ crystals is as high as 4000.     

Microwave dielectric properties of CaO–La2O3–Nb2O5–TiO2 ceramics

A series of ceramics with a general formula Ca_1+xLa_4?xNb_xTi_5?xO₁₇ (0 ≤ x ≤ 4) were fabricated using the solid-state ceramic route. The phase, microstructure, and microwave dielectric properties varied distinctly with composition or the value of x. X-ray diffraction results showed that the two end member phases, CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇, crystallized into single phases with orthorhombic and monoclinic crystal structure, respectively. For intermediate compounds with x = 1, 2, and 3, mixture phases CaLa₄Ti₅O₁₇ and Ca₅Nb₄TiO₁₇ coexisted and a trace amount of second phase was detected. The ceramics showed high ε _r in the range of 45–52, relatively high quality factors with Q × f in the range of 9,870–15,680 GHz and τ _f value in the range between ?38 and ?126.4 ppm/°C. τ _f of CaLa₄Ti₅O₁₇ can be tuned to a near-zero value by addition of suitable amount of TiO₂.     

Structural and Transport Properties of La2/3 – x Li3x □4/3 – 2x Ta2O6 Perovskite-Like Solid Solutions

The homogeneity range of La_2/3–x Li_{3x 4/3 – 2x} Ta₂O₆ perovskite-like solid solutions was determined. The transport properties of the La_2/3–x Li_{3x 4/3 – 2x} Ta₂O₆ oxides were shown to correlate with their lattice parameters and composition. Lithium-doped lanthanum metatantalate with an orthorhombically distorted perovskite-like structure is a good solid electrolyte with high lithium ion conductivity.     

Synthesis of ZnFe2O4–Zn2ZrO4Solid Solutions

Low-temperature plasma synthesis was used to prepare solid solutions ( and ) in the ZnFe₂O₄–Zn₂ZrO₄pseudobinary system. The Zn_{2 – x} Zr_{1 – x} Fe_2x O₄solid solutions were found to have a tetragonal spinel structure (a= 8.607–8.740 Å, c= 8.798–9.120 Å) in the composition range x= 0–0.55 and a cubic spinel structure (a= 8.447–8.539 Å) at x= 0.75–1.0. The tetragonal lattice distortion is attributed to a pseudo-Jahn–Teller effect. The electrical conductivity of the solid solutions shows semiconducting behavior and rises by a few orders of magnitude with increasing Fe³⁺content.     

Fine Structure of α-Al2O3-Based Solid Solutions

The fine structure of solid solutions between isomorphic p-block and 3dtransition-metal oxides was investigated experimentally and theoretically in the technologically important systems -Al₂O₃–M₂O₃(M = Ti, V, Cr, Fe). It was shown that the thermodynamic theory of isomorphic miscibility and conventional approaches to estimating solubility limits fail to explain and, at best, only predict the phase relations in the systems examined. The proposed magnetochemical method offers the possibility of studying in detail the M–M interactions in first-row oxides M₂O₃and (M _x Al_{1 – x} )₂O₃solid solutions, probing their homogeneity, and revealing their salient structural features. The marked difference in the solubilities of isomorphic M₂O₃oxides in -Al₂O₃is interpreted in terms of the magnetic structure of the oxides.     

Synthesis and Properties of (Sr1 – xMx)2Nb2O7 (M = Cu, Ni) Solid Solutions

(Sr_{1 – x} M _x )₂Nb₂O₇ (M = Cu, Ni) layered perovskite solid solutions were synthesized, and their stoichiometry ranges were determined. The electrical properties of the solid solutions were compared with those of Sr₂Nb₂O₇.     

Structure-Sensitive Properties of Melts and Thermal Properties of Glasses in the B2O3–CaO–Al2O3–PbO System

Inorganic Materials - The devitrification, “cold” crystallization, and glass transition temperatures and melting point of samples in the B2O3–CaO–Al2O3–PbO system have...     

Structural and Thermal Properties of Cu1 – xAgxInS2Chalcopyrite Solid Solutions

The anisotropic thermal expansion of Cu_{1 – x} Ag _x InS₂chalcopyrite solid solutions was studied by x-ray diffraction from 80 to 650 K. Over the entire temperature range studied, the thermal expansion of the solid solutions was found to be anisotropic: thec-axis thermal expansion is considerably smaller than thea-axis thermal expansion. The solid solutions with 0.55 <x< 1.0 exhibit negative c-axis thermal expansion. The composition dependences of the thermal expansion coefficients and anisotropy parameters are nonlinear. The anisotropy parameters rise monotonically with increasing x. The correlation between the thermal expansion anisotropy and tetragonal distortion = 2 – c/ais considered. Directions of zero thermal expansion are identified.     

Influence of Nb2O5 on the varistor behavior of TiO2–Cr2O3 system

This work investigated the influence of Nb₂O₅ dopant on the varistor behavior of the ternary system (99.95 ? x)%TiO₂, 0.05 %Cr₂O₃, x%Nb₂O₅, where x = 0.10; 0.15; 0.20; 0.25 % in mol. The processing was carried out using the conventional oxide mixture method. The initial oxides were homogenized in alcoholic media in a ball mill, for 3 h, dried in oven and isostatically pressed at 210 MPa and sintered at 1,400 °C for 2 h in air atmosphere and cooled at 5 °C/min cooling rate, resulting in pellets with high densification. Electrical measurements in continuous current at different temperatures revealed that for the lowest Nb₂O₅ concentration the breakdown electric field, E_B = 4.41 V/cm and non-linear coefficient, α = 4.6 were obtained, and for the highest Nb₂O₅ concentration the breakdown electric field, E_B = 9.71 V/cm and non-linear coefficient, α = 15.3 were obtained. These low values in the breakdown electric field enable these varistor systems to be used in protection systems for low-voltage energy grids. Changes in the potential barrier present in the grain–grain boundaries could also be observed, in which the height increased and the width decreased with the increase in the dopant concentration. However, for x = 0.25 % in mol Nb₂O₅, a significant reduction in the potential barrier height and the voltage per barrier was obtained. Furthermore, the tendency to increase the volume of the unitary cell with the increase of dopant concentration, which was interrupted in the system with 0.25 % Nb₂O₅, was another evidence that suggested the occurrence of Nb₂O₅ segregation in the grain boundaries, or even that the reduction in the average grain size could possibly dilute Nb₂O₅ concentration in the grain boundaries. The average grain size was calculated through SEM micrographs and ranged from 7 to 16 μm, with larger sizes occurring for lower dopant concentrations and presenting higher porosity and lower uniformity in the grains shape.     

Microwave dielectric properties of 3Li2O–Nb2O5–3TiO2 ceramics with Li2O–V2O5 additions

A new Li₂O–Nb₂O₅–TiO₂ (LNT) ceramic with the Li₂O:Nb₂O₅:TiO₂ mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li₂TiO₃ and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave dielectric properties of a relatively high permittivity (∼51), high Q × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li₂O–0.17V₂O₅ (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties of ε_r = 51.3, Q × f = 7235 GHz, τ _f  = 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices.     

Cation Conductivity of Li8ZrO6–LiYO2 Solid Solutions

The Li₈ZrO₆–LiYO₂ system is shown to contain two partial solid-solution series, which extend to 1 mol % LiYO₂ in Li₈ZrO₆ and 10 mol % Li₈ZrO₆ in LiYO₂. The electrical properties (temperature and composition dependences of conductivity, activation energy, and electronic conductivity) of LiYO₂ and Li₈ZrO₆–LiYO₂ solid solutions are studied.     

Ferroelectric Films of Ba0.7–0.8Sr0.2–0.3TiO3 Solid Solutions Deposited from Carboxylate Solutions

Ferroelectric films of Ba_0.7–0.8Sr_0.2–0.3TiO₃ solid solutions 2–3 m in thickness were deposited onto platinum substrates from carboxylate solutions and characterized by dielectric measurements at 1000 Hz: t _C = 15–16°C, ₂₀ > 1000, tan = 0.04–0.06 in the range 10–100°C. The controllability coefficient of the films in a dc electric field between 36 and 42°C is 1.6.     

Phase Relations in the Na2O–Al2O3–Nb2O5and CaO–Al2O3–Nb2O5Systems

Phase relations in the Na₂O–Al₂O₃–Nb₂O₅and CaO–Al₂O₃–Nb₂O₅systems were studied. The Na₂O system was found to contain neither ternary compounds nor niobate–aluminate solid solutions. In the CaO system, a ternary compound of composition 4CaO · Al₂O₃·Nb₂O₅was identified (cubic structure, a= 7.628 Å, Z= 2, _meas= _x= 4.43 g/cm³).     

Synthesis and Photoelectrochemical Properties of Cd4 – x Hg x GeS6 Solid Solutions

Cd₄GeS₆, Hg₄GeS₆, and Cd_{4 – x} Hg _x GeS₆ crystals are grown from presynthesized charges. The electrochemical and photoelectrochemical properties of a Cd_1.2Hg_2.8GeS₆ electrode are studied. The energy positions of the conduction-band and valence-band edges are compared for two samples having identical cation compositions but differing in anion composition.