Search results for "Solid solution"
showing 10 items of 308 documents
Phase diagram ofN2:Ar:CO solid solutions
1991
Ces solutions sont etudiees par diffraction des rayons X. Le diagramme de phase ternaire presente trois regions monophases (hc, cfc et Pa3) et de larges regions a deux phases (Pa3 cfc et hc cfc). On demontre l'influence de la vitesse de refroidissement sur la structure a basse temperature
Crystal structure of Bi_{6}Sr_{8-x}Ca_{3+x}O_{22}(-0.5\leq x\leq1.7)$: a mixed valence bismuth oxide related to perovskite
1998
Abstract: The crystal structure of BiSr8-xCa3+xO22 has been determined by single-crystal X-ray diffraction. This phase is the same as Bi9Sr11Ca5Oy that was previously studied by several authors as a secondary phase in the Bi-Sr-Ca-Cu-O system and coexists in thermodynamic equilibrium with the superconductors Bi2Sr2CuO6 and Bi2Sr2CaCu2O8 It crystallizes in the monoclinic space group P2(1)/c, with cell parameters a 11.037(3) Angstrom, b = 5.971(2) Angstrom, c = 19.703(7) Angstrom, beta = 101.46(3)degrees Z = 2. The structure was solved by direct methods and full-matrix least-squares refinement. It is built up by perovskite-related blocks of composition [Sr8-xBi2Ca3+xO16] that intergrow with d…
Aluminum and Gallium Substitution in Yttrium and Lutetium Aluminum–Gallium Garnets: Investigation by Single-Crystal NMR and TSL Methods
2016
The work reports the results on 71Ga and 27Al NMR investigation of the gallium and aluminum ions distribution over tetrahedral and octahedral positions in the Y3Al5−x GaxO12:Ce single crystals and Lu3Al5−xGaxO12:Ce single-crystalline epitaxial films. The gallium content x varies between 0 and 5 in crystals and between 0.3 and 2 in films.. We find that in both the Y- and Lu-based solid solutions the larger gallium ions are preferably located at the tetrahedral position while the smaller aluminum ions prefer the octahedral position of the garnet host. Based on NMR data, the dependence of fractional occupation parameters of the tetrahedral site of Ga and Al ions on the Ga content is determined…
Dielectric and acoustic properties of modified barium titanate ceramics
2019
This work was supported in part by the Ministry of Education and Science of the Russian Federation.
High-pressure crystal structure investigation of synthetic Fe2SiO4 spinel.
2011
AbstractThe crystal structure of Fe2SiO4 spinel at room temperature was investigated at seven different pressures by X-ray diffraction, using a diamond anvil cell to examine the influence of Fe substitution on ringwoodite behaviour at high pressure. The results compared with those of a pure Mg endmember show that the substitution of Fe into the spinel structure causes only small changes in the compression rate of coordination polyhedra and the distortion of the octahedron. The data show that the compression rate for the octahedron and tetrahedron in (Mg,Fe)2SiO4 can be considered statistically equal for FeO6 and MgO6, as well as for SiO4 in both the endmembers. This shows why almost identic…
The Kinetics of Excitonic Luminescence in Mixed Silver Halides
1994
ABSTRACTTwo kinds of luminescence (excitonic luminescence and excitonic molecule luminescence) were investigated for solid solutions AgBr1-xClx after pulsed electron beam and N2 laser irradiation. Careful theoretical treatment of a set of experimental excitonic luminescence kinetics is presented. It is shown that the effective activation energy of Agoi migration is a linear function of the composition x. The narrow peak of the excitonic molecule luminescence shifts from 2.66ev in pure AgBr towards higher energies as x increases.
Grain growth in Na 0.5 Bi 0.5 TiO 3 -based solid solutions
2019
This paper discusses effects of different dopants, sintering technique and parameters on microstructure and properties of pure and Yb, Er-doped Na0.5Bi0.5TiO3 (NBT). All stoichiometric compositions follow the abnormal grain growth mechanism (AGG) and exhibit a bimodal grain size distribution. Bi over-stoichiometry, two step sintering and hot pressing are effective inhibitors of AGG. Microstructure of sintered NBT greatly influences such properties as dielectric permittivity and depolarization temperature.
Low-temperature metastabilization of tetragonal V+4-containing ZrO2 solid solutions
2001
Abstract The formation and characterization of tetragonal vanadium–zirconia solid solutions with different vanadium contents have been investigated. Vanadium–zirconia precursors were prepared by gelling mixtures of zirconium n-propoxide and vanadyl acetylacetonate, and studied over the range of temperature up to the tetragonal–monoclinic phase transformation. The formation of the tetragonal phase has been investigated by X-ray powder diffraction (XRD). It was found that it took place after annealing around 450°C for all specimens independently of the vanadium loading. In contrast, the temperature for the subsequent tetragonal to monoclinic transformation was dependent on the nominal vanadiu…
Tuning the magnetic properties in the layered molecular based magnets A[FeIIRuxIIIM1−xIII(ox)3] (MIII=Cr or Fe; ox=oxalate; A=organic or organometall…
2001
Abstract The magnetic properties of the family of layered molecular magnets A[FeIIMIII(ox)3] (MIII=Cr, Fe, Ru; ox=oxalate; A+=[NBu4]+, [ CoCp 2 ∗ ] + ) are reported. In particular, a detailed magnetic study of the solid solutions FeII(RuIIICrIII) and FeII(RuIIIFeIII) has been undertaken. We show that in these magnets both, transition temperatures and coercive fields, can be easily tuned by changing the chemical composition of the material, i.e. the ratio RuIII/MIII (MIII=Cr, Fe) within the magnetic layers and the type of cation A+ inserted in between the layers. Coercive fields as high as 2.2 T have been reached in this way.
Freeze-dried precursor-based synthesis of new polymetallic oxynitrides, V1−u−zCruMoz(OxNy),V1−u−zCruWz(OxNy), Cr1−u−zMouWz(OxNy) (u, z=0.2, 0.33, 0.4…
2005
Abstract Interstitial polymetallic oxynitrides in the solid solution series V 1− u − z Cr u Mo z (O x N y ), V 1− u − z Cr u W z (O x N y ) and Cr 1− u − z Mo u W z (O x N y ) ( u , z = 0.2, 0.33, 0.4, 0.6, u + z z Cr z Mo z W z (O x N y ) ( z = 0.25) composition, can be obtained by ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the simple metal salts NH 4 VO 3 , (NH 4 ) 2 CrO 4 , (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and (NH 4 ) 6 W 12 O 39 ·18H 2 O. A study of the influence of the preparative variables on the outcomes of this procedure is presented. Compounds in the V 1− u − z Cr u Mo z (O x N y ) series have been prepared as single phases by direct ammonolys…