Lahrich S, Elmhammedi M A, Manoun B, Tamraoui Y, Mirinioui F, Azrour M, Lazor P
Univ. Hassan 1(er), Laboratoire des Sciences des Matériaux, des Milieux et de la Modélisation (LS3M), 25000 Khouribga, Morocco; Univ. Hassan 1(er), Laboratoire de Chimie et Modélisation Mathématique, 25000 Khouribga, Morocco.
Univ. Hassan 1(er), Laboratoire de Chimie et Modélisation Mathématique, 25000 Khouribga, Morocco.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Jun 15;145:493-499. doi: 10.1016/j.saa.2015.02.083. Epub 2015 Feb 26.
Synthesis of apatites, Na1-xKxCaPb3(PO4)3 0 ⩽ x ⩽ 1, with anion vacancy were carried out using solid state reactions. The solid solution of apatite-type structure crystallize in the hexagonal system, space group P63/m (No. 176). Rietveld refinements showed that around 90% of Pb(2+) cations are located in the (6h) sites, the left amount of Pb(2+) cations are located in the (4f) sites; 27-31% of Ca(2+) cations are located in the (6h) sites, the left amount of Ca(2+) cations are located in the (4f) sites. The ninefold coordination sites (4f) are also occupied by the K(+) and Na(+) monovalent ions. The structure can be described as built up from PO4 tetrahedra and Pb(2+)/Ca(2+) of sixfold coordination cavities (6h positions), which delimit void hexagonal tunnels running along [001]. These tunnels are connected by cations of mixed sites (4f) which are half occupied by Pb(2+)/Ca(2+) and half by Na(+)/K(+) mixed cations. The assignment of the observed frequencies in the Raman and infrared spectra is discussed on the basis of a unit cell group analysis and by comparison with other apatites. Vibrational spectra of all the compositions are similar and show some linear shifts of the frequencies as a function of the composition toward lower values due the substitutions of Na(+) by K(+) with a larger radius.
采用固态反应法合成了具有阴离子空位的磷灰石Na1-xKxCaPb3(PO4)3（0⩽x⩽1）。磷灰石型结构的固溶体在六方晶系中结晶，空间群为P63/m（编号176）。Rietveld精修结果表明，约90%的Pb(2+)阳离子位于(6h)位置，其余的Pb(2+)阳离子位于(4f)位置；27 - 31%的Ca(2+)阳离子位于(6h)位置，其余的Ca(2+)阳离子位于(4f)位置。九重配位位点(4f)也被K(+)和Na(+)单价离子占据。该结构可描述为由PO4四面体和六重配位空穴（6h位置）中的Pb(2+)/Ca(2+)构成，这些空穴界定了沿[001]方向延伸的六方空洞隧道。这些隧道通过混合位点(4f)的阳离子相连，该位点一半被Pb(2+)/Ca(2+)占据，一半被Na(+)/K(+)混合阳离子占据。基于晶胞群分析并与其他磷灰石进行比较，讨论了拉曼光谱和红外光谱中观测频率的归属。所有组成的振动光谱相似，并且由于半径较大的K(+)取代了Na(+)，频率随组成呈现出一些线性下降的变化。
