Affiliation:
1. Lobachevsky University, Nizhny Novgorod, Russia
Abstract
Apatites, being one of the most numerous mineral-like families of compounds,
are considered as a matrix for binding lead ions, which is dangerous for the
biosphere. The crystal-chemical (composition, structure) and thermophysical
aspects (thermal expansion) are considered as the basis for analyzing the
properties of this kind of material. It is suggested that substances of the
composition Pb5(AIVO4)2(BVIO4), Pb5(AIVO4)(CVO4)2 can be a perspective form
of lead binding materials based on compounds with the structure of apatite
(AIV = Si, Ge; BVI = S, Cr; CV = P). Such compounds, as it was shown by DTA
and HTXRD experiments, are distinguished by the absence of polymorphism and
abnormal ordering of the structure. Also, they have relatively low values of
thermophysical indicators (the rate of change of linear thermal expansion
coefficients is ~ 0.02-0.03?106 K-1 per K; values of the volume thermal
expansion coefficients are 40-70?106 K-1). Compounds Pb5(SiO4)(PO4)2 (a =
9.78782(16) ?, c = 7.31084(16) ?, V = 606.555(23) ?3, R-bragg = 4.694 %) and
Pb5(GeO4)(PO4)2 (a = 9.87697(12) ?, c = 7.33136(11) ?, V = 619.388(17) ?3,
R-bragg = 1.730 %) were obtained, identified and crystallographically
characterized for the first time.
Publisher
National Library of Serbia