Etude du systeme KFYbF3

Labeau, M.; Aléonard, S.; Vedrine, A.; Boutonnet, R.; Cousseins, J.C.

doi:10.1016/0025-5408(74)90131-7

Cited by 30 publications

(14 citation statements)

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“…As a result, we synthesized a badly crystallized sample of cubic -(or -)KYb F whose refined cell parameter was a" 11.301(5) A s (Note: the K½b F family exhibits three phases: !769°CP (hexagonal)!952°CP (cubic). ¹he and forms have been reported to be isotypic (10). ¹he P transformation is not observable by D¹A, but only by electric conductivity).…”

Section: Structural Descriptionmentioning

confidence: 96%

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

Maguer

Crosnier‐Lopez

Courbion

1997

Journal of Solid State Chemistry

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Section: Structural Descriptionmentioning

confidence: 96%

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

Maguer

Crosnier‐Lopez

Courbion

1997

Journal of Solid State Chemistry

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“…We have now shown that the cubic structures of KYaF~0 (Pierce &Hong, 1973), and its isotypes KTbaF~0 (Podberezskaya et al, 1976), a-and yKYbaF~0 (Labeau et aL, 1974), all strictly fluoriterelated, contain M6X36 units connected in such a way as to generate M6Xa2 groups. Moreover, as previously stated, both tveitite and NaTZr6F3~ are known structures containing M6X37 units, but not MrX32 groups, and we have succeeded so far in building from M6X37 units models of the as yet undetermined structures of M~I(RE)F7 and M~I(RE)sF33 (Greis, 1979), which are consistent with the known unit-cell geometries and space groups: these do not contain M 6 X32 groups either.…”

mentioning

confidence: 89%

A new structural principle in anion-excess fluorite-related superlattices

Bevan¹,

Greis²,

Strähle³

1980

Acta Cryst Sect A

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A preliminary report on the rhombohedral structure of the ordered yttrofluorite mineral, tveitite (possible formulae: Ca~a+sY6_~F44_ ~, Ca~4YsF4a or Ca~aY 6-F420), is given. In this structure discrete M6Xa7 groups occur, which consist of an octahedral arrangement of cation-centred square antiprisms sharing corners around the threefold axis to enclose a filled cuboctahedron of anions. The same group is found in other known fluorite-related superlattices, which suggests that it is a basic structural unit. Its formal derivation from the analogous element of fluorite is described.Most naturally-occurring yttrofluorite is a disordered, fluorite-type solid solution containing <20% (Y,RE)F 3. Recently, however, Bergstal, Jensen & Neumann (1977) reported an ordered yttrofluorite from Norway (tveitite) with about 30% (Y,RE)F 3, and an analogous mineral has been found independently by Crook (1978), occurring as small inclusions in normal yttrofluorite from the Barringer Hill district of Texas, USA.A small sample of the Norwegian tveitite was kindly made available to us, and further studies by powder X-ray and single-crystal electron diffraction have revealed its unit-cell geometry and place as the member n = 19 of the homologous series of fluorite-related compounds, MnX2~+ 5, in the system CaF2-YF 3 (Gettmann & Greis, 1978). A structure determination on tveitite has now been carried out. The full details will be reported subsequently, but we present here the result and, emerging from it, a new structural principle which explains the existence of the series * To whom correspondence should be addressed.0567-7394/80/060889-03 $01.00The tveitite unit cell is rhombohedral, with hexagonal parameters a = 16.9620 (9), c = 9.6664 (8) A, Z = 57, and the space group is either R3 or R3. The cations are displaced very little from their sites in the ideal fluorite structure, as is the case for most known fluorite-related superlattices, but the anion sublattice has undergone a major rearrangement with respect to that of fluorite. In order to describe this, and to emphasize the structural relationship between tveitite and its fluorite-type parent structure, we dissect from the latter and focus attention on an element which is an octahedron of six cations grouped around a threefold axis. In fluorite, each cation is coordinated by a cube of eight anions, and these MX s cubes share edges, so the relevant group, shown in Fig. l(a), consists of six MX s cubes sharing edges to generate an empty X s cube in its centre. Such groups then further edge-share to fill space: this description is of course not new. In the tveitite structure, modified units, based on the same grouping of six cations around the now unique threefold axis, appear as discrete entities, and the modification is simply that the cation (yttrium) coordination polyhedra have transformed to square antiprisms which, by incorporation of additional anions, now share corners, as shown in Fig. l(b), to enclose a cuboctahedron of anions. The centre of this cuboctahedron, as ...

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“…The thermoluminescence of KYF 4 /Tm 3þ was investigated by Coeck et al [17] Aleonard and co-workers synthesized pure and rare-earth-doped crystalline powders of KYF 4 or KY 3 F 10 by hydrothermal means. [18,19] The crystal structure of KYF 4 and KY 3 F 10 has been determined by single crystal X-ray analysis. KYF 4 crystallizes in the hexagonal crystallographic system (distorted fluoride structure) [18,20] whereas KY 3 F 10 displays a cubic structure which was recently investigated in detail by Friese et al [21] This investigation has shown that the structure is based on the fluorite type structure but with a superstructure.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Schäfer

Ptáček

Zerzouf

et al. 2008

Adv Funct Materials

214

129

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KYF4/Yb3+, Er3+ nanocrystals with a mean diameter of approximately 13 nm were synthesized at 200 °C in the high boiling organic solvent N‐(2‐hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize in the cubic phase known from α‐NaYF4 and form transparent colloidal solutions in tetraethylene glycol (TEG) or propanol. Solutions containing 1 wt % of the nanocrystals in TEG display visible upconversion emission upon continuous wave (CW) excitation at 978 nm. Growing undoped KYF4 on the surface of the KYF4/Yb3+, Er3+ nanocrystals increases the upconversion efficiency by more than a factor of 20. The XRD data of these particles, display a slight increase in the mean particle size from 13 to 15.5 nm, indicating that only a part of the subsequently added KYF4 shell material is deposited onto the particle surface. Nevertheless the performed surface modification obviously leads to core/shell structured particles.

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Etude du systeme KFYbF3

Cited by 30 publications

References 1 publication

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

A new structural principle in anion-excess fluorite-related superlattices

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

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Etude du systeme KFYbF3

Cited by 30 publications

References 1 publication

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

“Chimie Douce” Synthesis and ab Initio Structure Determination of (H3O)Yb3F10,H2O: Diamond Type Stacking of UOA[8]

A new structural principle in anion-excess fluorite-related superlattices

Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4

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Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄