A. G. Belous

The effect of partial isovalent substitution in the A-sublattice on MW properties of materials based on Ba6–xLn8+2x/3Ti18O54 solid solutions

Abstract Investigations of materials based on the three systems: (Ba 1– y Pb y ) 6– x La 8+2 x /3 Ti 18 O 54 , (Ba 1– y Pb y ) 6– x Nd 8+2 x /3 Ti 18 O 54 , and (Ba 1– y Ca y ) 6– x Ln 8+2 x /3 Ti 18 O 54 revealed that a partial isovalent substitution in cation sublattices allows the control of the electrophysical parameters of microwave dielectrics. The investigations were carried out over a wide range of x values. Data on the relationship between the crystal-cell parameters and the microwave dielectric properties ( e , Q , and t f ) have been obtained and related to the size of the isovalent ion residing at crystallographic sites in the A-sublattice. Based on the data obtained, a non-random distribution of Ca 2+ and Pb 2+ ions on different A-sites as a function of their concentration in different systems was concluded. Various temperature-stable microwave dielectrics, based on the above three systems, have been synthesized and shown to exhibit excellent MW properties.

Effects of Chemical Composition and Sintering Temperature on the Structure of La1 – xSrxMnO3 ± γ Solid Solutions

AbstractThe structural parameters of La1 – xSrxMnO3 ± γ solid solutions sintered at different temperatures are refined using chemical analysis, x-ray fluorescence, and Rietveld profile analysis data. The samples are shown to consist of two rhombohedrally distorted perovskite phases (sp. gr. R

Solid electrolytes based on lithium-containing lanthanum metaniobates

\overline 3

Fabrication and Properties of Semiconducting Barium Lead Titanate Ceramics Containing Low-Melting Glass Additions

c and R3m) identical in chemical composition and containing excess oxygen. The electrical properties and magnetoresistive response of the Sr-doped lanthanum manganite ceramics depend on the relative amounts of these phases. The origin of structural disordering in the materials studied is discussed.

Crystallographic, electrical, and magnetic properties of the system La0.7Sr0.3Mn1−xFexO3

Polycrystalline nonstoichiometric Ba(Co1/3Nb2/3)O3 (BCN) materials have been synthesized and investigated. Deviations from stoichiometry have been shown to lead to the formation of crystalline Ba6CoNb9O30 (barium deficiency) and Ba8CoNb6O24 (cobalt deficiency). The effect of phase composition on the microwave dielectric properties of BCN has been studied. The results demonstrate that the dielectric properties of BCN-based materials can be tuned by varying cobalt content. The materials obtained are high-Q microwave dielectrics with temperature-stable properties.

Oxidation state of copper ions in (La0.7Sr0.3)(Mn1 − xCux)O3 ± δ ceramics and their magnetic properties

Abstract The structure and transport properties of lithium-containing lanthanum metaniobates with defect-perovskite structure, La 2/3-x Li 3x □ 4/3-2x Nb 2 O 6 , have been studied. It has been shown that in the structure of La 2/3-x Li 3x □ 4/3-2x Nb 2 O 6 , Li + cations occupy, preferably, positions 1a in the range x =0−≈0.5, and occupy positions 1c (vacancies) at x >0.5. It has been noted that the direction 1c↔1c is energetically a more favorable pathway of lithium ion migration. It has been shown that the materials under investigation possess a high lithium ion-conductivity.

Effect of Isovalent Ba-Site Substitutions on the Properties of (Ba1 – x – yMyYx)TiO3(M = Ca, Sr, Pb) PTCR Ceramics

The formation of cobalt metaniobate, CoNb2O6, with the columbite structure has been studied, and possible ways of optimizing solid-state synthesis conditions have been examined. Single-phase CoNb2−yO6−2.5y has been obtained in the composition range 0 ≤ y ≤ 0.05. The microstructure and microwave dielectric properties of Co1−xNb2O6−x materials have been investigated. The results indicate that the electrical Q of the nonstoichiometric materials drops sharply for x > 0 because of the presence of Nb2O5 as an impurity phase. For x < 0, Q gradually decreases with increasing Co content, which is caused by the rise in lattice strain and presence of Co4Nb2O9 impurity.

Synthesis and microwave dielectric properties of Zn1+x Nb2O6+x

The structural parameters of yttrium-doped (Ba,Pb)TiO3 solid solutions containing low-melting B2O3–PbO–SiO2 (BPS) glass additions were determined by Rietveld powder-diffraction analysis. It is shown that the introduction of BPS enables dense, semiconducting ceramics containing up to 60 mol % PbTiO3 to be produced by solid-state reactions followed by sintering at markedly reduced temperatures. Increasing the Pb content increases the lattice strain in the solid solutions, while BPS additions have the opposite effect. Sintering of BPS-containing materials leads to the formation of (Ва1 – χ – yPbχYy )(Ti1 – δPbδ)O3 solid solutions on grain surfaces (core–shell structure).