TY - JOUR

T1 - Crystal chemistry of stanfieldite, Ca7 M2 Mg9 (PO4)12 (M = Ca, Mg, Fe2+), a structural base of Ca3 Mg3 (Po4)4 phosphors

AU - Britvin, Sergey N.

AU - Krzhizhanovskaya, Maria G.

AU - Bocharov, Vladimir N.

AU - Obolonskaya, Edita V.

N1 - Funding Information: Acknowledgments: The authors gratefully acknowledge the curators of the Mining Museum, Saint Petersburg Mining University, for providing the sample of the Brahin meteorite used in this study. We are thankful to Funding: This research was financially supported by the Russian Science Foundation, grant number anonymous reviewers for their comments and suggestions. This research was supported by the resource Centre for X-ray diffraction studies and the Geomodel resource centre of Saint Petersburg State University.

PY - 2020/6/1

Y1 - 2020/6/1

N2 - Stanfieldite, natural Ca-Mg-phosphate, is a typical constituent of phosphate-phosphide assemblages in pallasite and mesosiderite meteorites. The synthetic analogue of stanfieldite is used as a crystal matrix of luminophores and frequently encountered in phosphate bioceramics. However, the crystal structure of natural stanfieldite has never been reported in detail, and the data available so far relate to its synthetic counterpart. We herein provide the results of a study of stanfieldite from the Brahin meteorite (main group pallasite). The empirical formula of the mineral is Ca8.04 Mg9.25 Fe0.72 Mn0.07 P11.97 O48. Its crystal structure has been solved and refined to R1 = 0.034. Stanfieldite from Brahin is monoclinic, C2/c, a 22.7973(4), b 9.9833(2), c 17.0522(3) Å, β 99.954(2)◦, V 3822.5(1)Å3. The general formula of the mineral can be expressed as Ca7 M2 Mg7 (PO4)12 (Z = 4), where the M = Ca, Mg, Fe2+. Stanfieldite from Brahin and a majority of other meteorites correspond to a composition with an intermediate Ca≈Mg occupancy of the M5A site, leading to the overall formula ~Ca7 (CaMg)Mg9 (PO4)12 ≡ Ca4 Mg5 (PO4)6. The mineral from the Lunar sample “rusty rock” 66095 approaches the M = Mg end member, Ca7 Mg2 Mg9 (PO4)12. In lieu of any supporting analytical data, there is no evidence that the phosphor base with the formula Ca3 Mg3 (PO4)4 does exist.

AB - Stanfieldite, natural Ca-Mg-phosphate, is a typical constituent of phosphate-phosphide assemblages in pallasite and mesosiderite meteorites. The synthetic analogue of stanfieldite is used as a crystal matrix of luminophores and frequently encountered in phosphate bioceramics. However, the crystal structure of natural stanfieldite has never been reported in detail, and the data available so far relate to its synthetic counterpart. We herein provide the results of a study of stanfieldite from the Brahin meteorite (main group pallasite). The empirical formula of the mineral is Ca8.04 Mg9.25 Fe0.72 Mn0.07 P11.97 O48. Its crystal structure has been solved and refined to R1 = 0.034. Stanfieldite from Brahin is monoclinic, C2/c, a 22.7973(4), b 9.9833(2), c 17.0522(3) Å, β 99.954(2)◦, V 3822.5(1)Å3. The general formula of the mineral can be expressed as Ca7 M2 Mg7 (PO4)12 (Z = 4), where the M = Ca, Mg, Fe2+. Stanfieldite from Brahin and a majority of other meteorites correspond to a composition with an intermediate Ca≈Mg occupancy of the M5A site, leading to the overall formula ~Ca7 (CaMg)Mg9 (PO4)12 ≡ Ca4 Mg5 (PO4)6. The mineral from the Lunar sample “rusty rock” 66095 approaches the M = Mg end member, Ca7 Mg2 Mg9 (PO4)12. In lieu of any supporting analytical data, there is no evidence that the phosphor base with the formula Ca3 Mg3 (PO4)4 does exist.

KW - Bioceramics

KW - Crystal structure

KW - Luminophore

KW - Merrillite

KW - Mesosiderite

KW - Meteorite

KW - Pallasite

KW - Phosphate

KW - Powder diffraction

KW - Raman spectroscopy

KW - Stanfieldite

UR - http://www.scopus.com/inward/record.url?scp=85086164587&partnerID=8YFLogxK

U2 - 10.3390/cryst10060464

DO - 10.3390/cryst10060464

M3 - Article

AN - SCOPUS:85086164587

VL - 10

SP - 1

EP - 14

JO - Liquid Crystals Today

JF - Liquid Crystals Today

SN - 1358-314X

IS - 6

M1 - 464

ER -