Elaboration, Rietveld Refinements and Vibrational Spectroscopic Studies of a new Lacunar Apatite Series: NaPb3-x CaxCd(PO4)3 (0 ≤ × ≤ 1)

2018 ◽  
Vol 42 (11) ◽  
pp. 564-571
Author(s):  
Meryem Ben Baaziz ◽  
M'barek Azdouz ◽  
Mohamed Azrour ◽  
Abdelkrim Batan ◽  
Bouchaib Manoun
Keyword(s):  
Solid Solution ◽  
Vibrational Spectra ◽  
Rietveld Method ◽  
Spectroscopic Studies ◽  
Solid Solution Series ◽  
Hexagonal System ◽  
Rietveld Refinements ◽  
Solution Series ◽  
Group A ◽  
Good Agreement

The solid–solution series NaPb3-xCaxCd(PO4)3 (0 ≤ × ≤ 1) has been synthesised and crystallised in the hexagonal system with the P63/m space group. A refinement study using the Rietveld method shows good agreement between the observed and calculated patterns. The structure can be described as built up from [PO4]3- tetrahedra and Pb2+/Cd2+/Ca2+ of six-fold 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 Pb2+/Cd2+/Ca2+ and half by Na+ cations. The vibrational spectra of all the compositions are similar and show some linear shifts as a function of the composition towards lower values due to the substitutions of Pb2+ by Ca2+ with a smaller radius.

Rietveld refinement of the solid-solution series: (Cu,Mg)SO4·H2O

1995 ◽  
Vol 10 (3) ◽  
pp. 189-194 ◽  
Author(s):  
C. L. Lengauer ◽  
G. Giester
Keyword(s):  
Solid Solution ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Solid Solution Series ◽  
Cation Site ◽  
Tg Analysis ◽  
X Ray ◽  
Solution Series

The kieserite-type solid-solution series of synthetic (Cu,Mg)SO4·H2O was investigated by TG-analysis and X-ray powder diffraction using the Rietveld method. Representatives with Cu≥20 mol% are triclinic distorted () analogous to the poitevinite (Cu,Fe)SO4·H2O compounds. Cation site ordering with preference of Cu for the more distorted M1 site was additionally proven by the structure refinement.

The eudialyte group: a review

2001 ◽  
pp. 65-72 ◽  
Author(s):  
Ole Johnsen ◽  
Joel D. Grice ◽  
Robert A. Gault
Keyword(s):  
Solid Solution ◽  
Empirical Formula ◽  
Sensu Stricto ◽  
Solid Solution Series ◽  
Eudialyte Group ◽  
Original Series ◽  
Minor Elements ◽  
Solution Series ◽  
Wide Range ◽  
Group A

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Johnsen, O., Grice, J. D., & Gault, R. A. (2001). The eudialyte group: a review. Geology of Greenland Survey Bulletin, 190, 65-72. https://doi.org/10.34194/ggub.v190.5174 _______________ The eudialyte group of complex Na, Ca, Zr silicates encompasses a wide range of compositions in which all the main elements Si, Zr, Ca, Fe and Na vary, and many relatively minor elements such as Mn, REE, Sr Nb, K, Y and Ti are present. For most members of the group the empirical formula is Na15[M(1)]6[M(2)]3Zr3[M(3)](Si25O73)(O,OH,H2O)3(Cl,F,OH)2 and the best method of formula calculation is on the basis of 29 (Si, Al, Zr Ti, Hf, Nb, W, Ta) apfu (Z = 3), which are the elements assigned to the Zr, M(3) and all Si sites in the structure. The commonest substitutions are found with the solid solution series eudialyte sensu stricto (enriched in Si, Ca, Fe and Cl) and kentbrooksite (enriched in Nb, REE, Mn and F), but recent studies show that the series extends beyond kentbrooksite to an exceptionally Ca-deficient eudialyte now named oneillite. Most eudialytes are trigonal R3m or R3m but oneillite is R3. Additional members of the group are khomyakovite and manganokhomyakovite.

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