THE CRYSTAL-STRUCTURE OF STILLWELLITE

被引：0

作者：

BURNS, PC ^{[1
]}

HAWTHORNE, FC ^{[1
]}

MACDONALD, DJ ^{[1
]}

DELLA VENTURA, G ^{[1
]}

PARODI, GC ^{[1
]}

机构：

[1] UNIV ROMA LA SAPIENZA, DIPARTIMENTO SCI TERRA, SEZ MINERAL CRISTALLOG, I-00185 ROME, ITALY

来源：

CANADIAN MINERALOGIST | 1993年 / 31卷

关键词：

STILLWELLITE; CRYSTAL STRUCTURE; PHASE TRANSITION; CHEMICAL COMPOSITION; RARE-EARTH ELEMENTS; VETRALLA; VICO VOLCANO; ITALY;

D O I：

暂无

中图分类号：

P57 [矿物学];

学科分类号：

070901 ;

摘要：

Stillwellite,X[BO(SiO4)], where X represents Ce and La (dominant), with lesser Pr, Nd and Th, is trigonal, a6.841(2), c6.702(2) angstrom, V271.7(2) angstrom3, Z = 3, space group P3(1); its structure has been refined by least-squares methods to an R index of 2.7% using 1003 observed [F > 5sigma(F)] reflections. Stillwellite contains helical chains of (BO4) tetrahedra polymerized by sharing comers. These chains are decorated by (SiO4) tetrahedra that share two comers with adjacent (BO4) tetrahedra. Large, irregular 9-coordinate REE sites link the polyhedral chains. Stillwellite most likely has P3(1)21 symmetry at high temperatures and undergoes a ferroelectric phase-transition to P3(1) upon cooling.

引用

页码：147 / 152

页数：6

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