Тип публикации: статья из журнала
Год издания: 2018
Идентификатор DOI: 10.1007/s00269-017-0903-4
Ключевые слова: Grandreefite, Selenate, Fluoride, Litharge, Thermal decomposition, Anion-centered tetrahedra
Аннотация: Co-precipitation of PbF2 and PbSeO4 in weakly acidic media results in the formation of [Pb2F2](SeO4), the selenate analogue of the naturally occurring mineral grandreefite, [Pb2F2](SO4). The new compound is monoclinic, C2/c, a = 14.0784(2) , b = 4.6267(1) , c = 8.8628(1) , beta = 108.98(1)A degrees, V = 545.93(1) (3). Its structureПоказать полностьюhas been refined from powder data to R (B) = 1.55%. From thermal studies, it is established that the compound is stable in air up to about 300 A degrees C, after which it gradually converts into a single phase with composition [Pb2O](SeO4), space group C2/m, and lattice parameters a = 14.0332(1) , b = 5.7532(1) , c = 7.2113(1) , beta = 115.07(1)A degrees, V = 527.37(1) (3). It is the selenate analogue of lanarkite, [Pb2O](SO4), and phoenicochroite, [Pb2O](CrO4), and its crystal structure was refined to R (B) = 1.21%. The formation of a single decomposition product upon heating in air suggests that this happens by a thermal hydrolysis mechanism, i.e., Pb2F2SeO4 + H2O (vapor) -> Pb2OSeO4 + 2HFa dagger. This relatively low-temperature process involves complete rearrangement of the crystal structure-from a 2D architecture featuring slabs [Pb2F2](2+) formed by fluorine-centered tetrahedra into a structure characterized by 1D motifs based on [OPb2](2+) chains of oxocentered tetrahedra. The comparative crystal chemistry of the obtained anion-centered structural architectures is discussed.
Журнал: PHYSICS AND CHEMISTRY OF MINERALS
Выпуск журнала: Vol. 45, Is. 1
Номера страниц: 69-76
ISSN журнала: 03421791
Место издания: NEW YORK
Издатель: SPRINGER