scholarly journals Investigation into the structural features and microwave absorption of doped barium hexaferrites

2017 ◽  
Vol 46 (28) ◽  
pp. 9010-9021 ◽  
Author(s):  
S. V. Trukhanov ◽  
A. V. Trukhanov ◽  
V. G. Kostishyn ◽  
L. V. Panina ◽  
An. V. Trukhanov ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Structural Features ◽  
Unit Cell ◽  
Ceramic Technology ◽  
Magnetic Parameters ◽  
Barium Hexaferrites ◽  
Monotonically Decrease

BaFe12−xGaxO19 hexaferrites were synthesized via the usual ceramic technology; with an increase in x, the unit cell and magnetic parameters monotonically decrease.

Two phases of {[CsPH(η6-2,4,6- t Bu3C6H2)]2(η3-toluene)0.5} x : their structures and interconversions

2000 ◽  
Vol 56 (2) ◽  
pp. 210-214
Author(s):  
Thomas E. Concolino ◽  
Kin-Chung Lam ◽  
Ilia A. Guzei ◽  
Arnold L. Rheingold ◽  
Gerd W. Rabe
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Unit Cell Volume ◽  
Structural Features ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Disorder Phase Transition ◽  
Two Phases ◽  
A Minor

The solvent-bridged caesium phosphide {[CsPH(η 6-2,4,6- t Bu3C6H2)]2(η 3-toluene)0.5} x , catena-[(μ-η3-toluene)-bis[caesium(2,4,6-tri-tert-butylphenylphosphide)]], undergoes a reversible solid-state, order–disorder phase transition characterized by the doubling of the unit-cell volume at low temperature achieved by doubling one unit-cell vector. The unit-cell parameters at 293 (2) K (form A) are: a = 11.147 (4), b = 14.615 (4), c = 14.806 (5) Å, α = 70.57 (3), β = 71.85 (3), γ = 72.93 (2)°, V = 2112.5 (12) Å3, Z = 2, ρcalc = 1.362 g cm−3, R 1 = 0.0513 for 5462 reflections, wR 2 = 0.0947 for all data. The unit-cell parameters at 173 (2) K (form B) are: a = 14.6241 (3), b = 14.7393 (3), c = 22.0720 (4) Å, α = 72.2117 (7), β = 73.3659 (8), γ = 70.2953 (7)°, V = 4174.8 (2) Å3, Z = 4, ρcalc = 1.379 g cm−3, R 1 = 0.0405 for 14 010 reflections, wR 2 = 0.1326 for all data. With a minor change, the key structural features discussed previously for form A [Rabe et al. (1998). Inorg. Chem. 37, 4235–4245] remain unchanged. The η 3-toluene ligand is observed to be disordered at 293 (2) K and ordered at 173 (2) K, with the order–disorder phase transition occurring at approximately 278 (2) K.

Crystal Structure Explains Crystal Habit for the Antiviral Drug Rimantadine Hydrochloride

2014 ◽  
Vol 69 (7) ◽  
pp. 823-828 ◽  
Author(s):  
Anatoly Mishnev ◽  
Dmitrijs Stepanovs
Keyword(s):  
Crystal Structure ◽  
Symmetry Axis ◽  
Antiviral Drug ◽  
Structural Features ◽  
Unit Cell ◽  
Crystal Habit ◽  
Maximal Dimension ◽  
X Ray ◽  
Rimantadine Hydrochloride ◽  
Inner Channel

The crystal structure of the antiviral drug rimantadine hydrochloride, C12H22N+ Cl−, has been elucidated by a single-crystal X-ray structure analysis. The structure consists of 1-(1- adamantyl)ethanamine (rimantadinium) cations and chloride anions. The Cl− anions link the rimantadinium cations via N-H...Cl hydrogen bonds into infinite rectangular chord-like structural units with charged groups in the inner channel and aliphatic groups on the surface, and oriented along the unit cell c axis. In contrast to strong electrostatic and hydrogen bonding inner interactions the chords in the crystal are held together by weak van der Waals forces only. A two-fold symmetry axis passes through the center of the chord. By indexing of the crystal faces it has been shown that the maximal dimension of the needle-like crystals coincides with the direction of the unit cell c axis. These structural features explain the crystal habit and the anisotropy of the mechanical properties of rimantadine hydrochloride crystals observed upon slicing and cleavage.

Multiferroic properties and structural features of M-type Al-substituted barium hexaferrites

2017 ◽  
Vol 59 (4) ◽  
pp. 737-745 ◽  
Author(s):  
A. V. Trukhanov ◽  
S. V. Trukhanov ◽  
V. G. Kostishin ◽  
L. V. Panina ◽  
M. M. Salem ◽  
...  
Keyword(s):  
Structural Features ◽  
Multiferroic Properties ◽  
Barium Hexaferrites

scholarly journals Destruction phenomena in ferroactive materials

2020 ◽  
Vol 10 (04) ◽  
pp. 2050012
Author(s):  
Sidek Khasbulatov ◽  
Aleksander Cherpakov ◽  
Ivan Parinov ◽  
Konstantin Andryushin ◽  
Lidiya Shilkina ◽  
...  
Keyword(s):  
Solid Phase ◽  
Bismuth Ferrite ◽  
Structural Features ◽  
Strength Properties ◽  
Ceramic Technology ◽  
Grain Structure ◽  
Structural Elements ◽  
Phase Synthesis ◽  
Local Stresses ◽  
Comprehensive Study

The results of a comprehensive study of the crystal structure, grain structure, and strength properties of ceramic bismuth ferrite with rare earth elements (REE) obtained by two-stage solid-phase synthesis followed by sintering using conventional ceramic technology are presented. The reasons for the formation of low mechanical strength and the development of destruction phenomena in solid solutions with small REE ([Formula: see text] Å) are considered: Tb, Dy, Ho, Er, Tm, Yb, Lu. The causes of the observed phenomena associated with the composite-like structure of the studied media and, as a consequence, the occurrence of local stresses of structural elements that provoke crack formation are established. A source of the latter are also the structural features of the grain landscape. The conclusion is made about the appropriateness of taking into account the information obtained when developing devices based on BiFeO3/REE multiferroics.

scholarly journals The structure of kaliophilite KAlSiO4, a long-lasting crystallographic problem

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1070-1083 ◽  
Author(s):  
Enrico Mugnaioli ◽  
Elena Bonaccorsi ◽  
Arianna E. Lanza ◽  
Erik Elkaim ◽  
Virginia Diez-Gómez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structural Features ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Channel System ◽  
X Ray ◽  
Cell Parameters ◽  
Peak Broadening ◽  
Structure Solution

Kaliophilite is a feldspathoid mineral found in two Italian magmatic provinces and represents one of the 12 known phases with composition close to KAlSiO4. Despite its apparently simple formula, the structure of this mineral revealed extremely complex and resisted structure solution for more than a century. Samples from the Vesuvius–Monte Somma and Alban Hills volcanic areas were analyzed through a multi-technique approach, and finally the crystal structure of kaliophilite was solved using 3D electron diffraction and refined against X-ray diffraction data of a twinned crystal. Results were also ascertained by the Rietveld method using synchrotron powder intensities. It was found that kaliophilite crystallizes in space group P3 with unit-cell parameters a = 27.0597 (16), c = 8.5587 (6) Å, V = 5427.3 (7) Å3 and Z = 54. The kaliophilite framework is a variant of the tridymite topology, with alternating SiO4 and AlO4 tetrahedra forming sheets of six-membered rings (63 nets), which are connected along [001] by sharing the apical oxygen atoms. Considering the up (U) and down (D) orientations of the linking vertex, kaliophilite is the first framework that contains three different ring topologies: nine (1-3-5) (UDUDUD) rings, six (1-2-3) (UUUDDD) rings and twelve (1-2-4) (UUDUDD) rings. This results in a relatively open (19.9 tetrahedra nm−3) channel system with multiple connections between the double six-ring cavities. Such a framework requires a surprisingly large unit cell, 27 times larger than the cell of kalsilite, the simplest phase with the same composition. The occurrence of some Na for K substitution (3–10%) may be related to the characteristic structural features of kaliophilite. Micro-twinning, pseudo-symmetries and anisotropic hkl-dependent peak broadening were also detected, and they may account for the elusive character of the kaliophilite crystal structure.

scholarly journals Influence of aluminum substitution on the fi eld of effective magnetic anisotropy and the degree of magnetic texture of anisotropic polycrystalline hexagonal ferrites of barium and strontium for substrates of microstrip devices of microwave electronics

2019 ◽  
Vol 21 (3) ◽  
pp. 166-174
Author(s):  
S. V. Shcherbakov ◽  
A. G. Nalogin ◽  
V. G. Kostishin ◽  
A. A. Alekseev ◽  
E. A. Belokon ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Anisotropy Field ◽  
Ceramic Technology ◽  
Preparation Technology ◽  
Magnetic Texture ◽  
Strontium Hexaferrites ◽  
Barium Hexaferrites ◽  
Microwave Electronics ◽  
Effective Magnetic Anisotropy ◽  
First Time

Abstract. In this paper, the effect of Al3+ ions substitutions on the value of the effective magnetic anisotropy field НАeff and the degree of magnetic texture f of the anisotropic polycrystalline hexagonal barium and strontium ferrites were studied. The samples were obtained by the ceramic technology method and the texture was formed by pressing in a magnetic field. The sample preparation technology presented in detail. The batches of barium hexaferrites were synthesized with the concentration of Al3+ ions: 0.9; 1.4; 2.5 and 2.6 formula units while strontium hexaferrites had Al3+ concentration of 0.1 formula units. It has been shown that by this technology barium and strontium hexaferrites with high value of (in range of 19—35 kOe) and with f = 80—83% could be obtained. The achieved values of НАeff and f could be sufficient for the production of substrates for microstrip microwave devices in millimeter−wave region.For the first time a raise in the degree of magnetic texture of polycrystalline barium hexaferrites with an increase of concentration of Al3+ ions were detected; a slight (5.5—5.8%) magnetic texture of isotropic strontium hexaferrites was also detected. The achieved results discussed in detail. For studied hexaferrites the mechanism of magnetic texture formation during the process of synthesis is proposed.

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