Crystal chemistry of MIIM′IV(PO4)2 double monophosphates

Abstract

a b s t r a c t M II M′ IV (PO 4 ) 2 compounds have been extensively studied for several decades for their potential applications in the field of several domains such as matrices for actinides conditioning, phosphors etc. In this paper, the relationships between composition and crystal structure of these compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. M II M′ IV (PO 4 ) 2 structures stem from two different archetypes: the cheralite and the yavapaiite structures, with some exceptions that are also described in this article. The ratio of the cations radii appears to be the most relevant parameter. The high ratio between the ionic radii of the divalent and tetravalent cations in yavapaiite derivates results in the ordering of these cations into well-differentiated polyhedra whereas cheralite is the only non-ordered structure encountered for M II M′ IV (PO 4 ) 2 compounds.

Structure, infrared and Raman spectroscopic studies of newly synthetic AII(SbV0.50FeIII0.50)(PO4)2 (ABa, Sr, Pb) phosphates with yavapaiite structure

“…Diffraction lines with I obs < 1 are omitted. relationships between composition and crystal structure [20]. Indeed we can conclude that for alkaline earth metal cations of smaller and/or equal size than the Ca 2þ ions, the [SbFe(PO 4 ) 3 ] À Nasicon framework seems to be the most stable.…”

“…In fact, their structure is strongly dependant to the nature and/or size of the A II and M IV cations. More recently the relationships between composition and crystal structure of some A II-M IV (PO 4 ) 2 compounds were established [20]. Thus, Morin et al have shown that the structure of PbSn(PO 4 ) 2 (space group P2 1 /n) is related to the yavapaiite type but the lead atoms are located in zigzag tunnels instead of layers [10].…”

Synthesis and characterisation of PuPO4 - a potential analytical standard for EPMA actinide quantification

“…If the crystal remains reasonably homogeneous and robust despite the lack of crystallinity and ingrowth of decay products, this method could be viable. Tetravalent actinides, such as Np and Th can be synthesized as a cheralite analogue (M 2+ M' 4+ )(PO 4 ) 2 [18]. Testing is required to determine if the cheralite analogue is sufficiently homogeneous to serve as a microprobe reference material.…”

Large easy-axis anisotropy in the one-dimensional magnet BaMo(PO4)2

“…Depending on the relative A and B-site ionic radii, the anhydrous alums may crystallize in either rhombohedral, trigonal, or monoclinic structures. In the monoclinic case, the B-site magnetic ions form an anisotropic triangular lattice as illustrated in Fig.1, whilst in the other two cases, an isotropic (equilateral) triangular lattice is realised 5 . Given this, as well as their chemical flexibility, a range of low-dimensional, frustrated, and anisotropic models can potentially be re-alized in the anhydrous alums.…”