ChemInform Abstract: Disordered Structures of Rare‐Earth Scandoborates of the Huntite Family.

Кузьмичева, Г. М.; Rybakov, Victor B.; Novikov, S. G.; Ageev, A. Yu.; Kutovoĭ, S. A.; Кузьмін, О. В.

doi:10.1002/chin.199935015

Cited by 3 publications

(4 citation statements)

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“…This conclusion is based on certain effects observed in the diffraction patterns, which are characteristic of the OD structures: (i) a presence of diffuse areas along with the point ones; (ii) a presence of diffraction reflections of a high symmetry; (iii) a difficulty in determining a real space group; (iv) similar a and b unit cell parameters and a multiple c parameter (for classical polytypes), wherein, for the huntite family compounds, the b parameters are the same, and the a and c parameters can be represented as a linear combination of vectors. For example, the unit cell parameters of the huntite family structures with the space groups R 32 and C 2/ c are correlated as a C 2/ c = 0.666( c R 32 2 + 0.75 b R 32 2 ) 1/2 , b C 2/ c = b R 32 , c C 2/ c = 0.666(4 c R 32 2 + 0.75 b R 32 2 ) 1/2 …”

Section: Results and Discussionmentioning

confidence: 99%

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄

Кузьмичева

Kaurova

Rybakov

et al. 2018

Crystal Growth & Design

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An influence of the type of rare-earth (RE) cation and composition of initial charge on the symmetry, structural features, and real composition of the single-crystal huntite family rare-earth scandium borates RESc3(BO3)4 (RE = Ce, Pr, Nd), grown by the Czochralski method, has been studied by single crystal and powder X-ray diffraction. A crystallization of scandium borates in the space groups C2/c (RE = Ce) and P321 (RE = Pr, Nd) has been found. Disordering in the structures with the space group P321, which has been first determined for the huntite family compounds, is due to the RE and Sc redistribution over two trigonal-prismatic sites to maintain the stability of crystal structure. The crystals grown from the initial charges NdSc3(BO3)4 and Nd1.25Sc2.75(BO3)4 are characterized by the greatest disordering, and they are isotypic, rather than isostructural, to the crystals obtained from the charges Pr1.1Sc2.9(BO3)4 and Pr1.25Sc2.75(BO3)4. A change in the unit cell parameters and interatomic distances depending on the RE radius and composition of the initial charge is found and explained. Analysis of our and literary data for RESc3(BO3)4 with the RE = La, Ce, Pr, Nd, Sm, Eu allowed to reveal a morphotropic series for scandium borates based on the size factor (the RE 3+ radius), suggest methods for evaluating the specific crystal symmetry depending on the type of RE cation, and propose factors affecting its realization. The comparison of huntite family REM 3(BO3)4 (M = Al, Ga, Sc) single crystals allowed to establish basic differences between their crystal structures, mainly due to the different sizes of RE and M ions.

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Section: Results and Discussionmentioning

confidence: 99%

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄

Кузьмичева

Kaurova

Rybakov

et al. 2018

Crystal Growth & Design

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“…For the above-mentioned compounds, positional parameters have been refined only [90]. [35,76,82,83,85,89,91] and [35,84,86,87,91], respectively, and in the present work. To reduce an error associated with an absorption, the XRD data were collected over the entire Ewald sphere.…”

Section: Methodsmentioning

confidence: 99%

Crystal Growth of Multifunctional Borates and Related Materials

2019

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“…Resuts of XRD study of the Czochralski-grown single crystals and solid solutions ("Enraf-Nonius" CAD-4 single-crystal diffractometer; room temperature; AgK α , MoK α or CuK α ; size,~0.1 × 0.1 × 0.1 mm 3 ) with the initial compositions LaSc 3 (BO 3 ) 4 , CeSc 3 (BO 3 ) 4 , Pr 4 , performed by our scientific group, are given in [35,76,82,83,85,89,91] and [35,84,86,87,91], respectively, and in the present work. To reduce an error associated with an absorption, the XRD data were collected over the entire Ewald sphere.…”

Section: Space Groups For the Lnm 3 (Bo 3 )mentioning

confidence: 99%

“…Beregi et al [97] concluded that the starting crystallization temperature is a dominant factor in formation of the trigonal and monoclinic symmetry: for the phase with the nominal composition Eu 0.02 Tb 0.12 Gd 0. 86 Rare-earth scandium orthoborates, unlike other huntite-family rare-earth borates, exhibit a slightly different structural behavior. For example, for the LaSc 3 (BO 3 ) 4 , three modifications are known: a low-temperature (space group Cc, is a subgroup of the space group C2/c and it is absent for other rare-earth orthoborates), a medium-temperature (space group R32; as was mentioned above, this group is denied by many researchers) and a high-temperature (space group C2/c) ones.…”

Section: Crystallochemical Features Of the Huntite Familymentioning

confidence: 99%

Crystallochemical Design of Huntite-Family Compounds

et al. 2019

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Huntite-family nominally-pure and activated/co-activated LnM3(BO3)4 (Ln = La–Lu, Y; M = Al, Fe, Cr, Ga, Sc) compounds and their-based solid solutions are promising materials for lasers, nonlinear optics, spintronics, and photonics, which are characterized by multifunctional properties depending on a composition and crystal structure. The purpose of the work is to establish stability regions for the rare-earth orthoborates in crystallochemical coordinates (sizes of Ln and M ions) based on their real compositions and space symmetry depending on thermodynamic, kinetic, and crystallochemical factors. The use of diffraction structural techniques to study single crystals with a detailed analysis of diffraction patterns, refinement of crystallographic site occupancies (real composition), and determination of structure–composition correlations is the most efficient and effective option to achieve the purpose. This approach is applied and shown primarily for the rare-earth scandium borates having interesting structural features compared with the other orthoborates. Visualization of structures allowed to establish features of formation of phases with different compositions, to classify and systematize huntite-family compounds using crystallochemical concepts (structure and superstructure, ordering and disordering, isostructural and isotype compounds) and phenomena (isomorphism, morphotropism, polymorphism, polytypism). Particular attention is paid to methods and conditions for crystal growth, affecting a crystal real composition and symmetry. A critical analysis of literature data made it possible to formulate unsolved problems in materials science of rare-earth orthoborates, mainly scandium borates, which are distinguished by an ability to form internal and substitutional (Ln and Sc atoms), unlimited and limited solid solutions depending on the geometric factor.

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ChemInform Abstract: Disordered Structures of Rare‐Earth Scandoborates of the Huntite Family.

Cited by 3 publications

References 0 publications

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄

Crystal Growth of Multifunctional Borates and Related Materials

Crystallochemical Design of Huntite-Family Compounds

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ChemInform Abstract: Disordered Structures of Rare‐Earth Scandoborates of the Huntite Family.

Cited by 3 publications

References 0 publications

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc3(BO3)4

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc3(BO3)4

Crystal Growth of Multifunctional Borates and Related Materials

Crystallochemical Design of Huntite-Family Compounds

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Product

Resources

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Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄

Structural Instability in Single-Crystal Rare-Earth Scandium Borates RESc₃(BO₃)₄