PREPARATION AND STRUCTURE OF THE YTTRIUM PHOSPHATE DIHYDRATE YPO4^|^middot;2H2O

Abstract

The yttrium phosphate dihydrate YPO4·2H2O was synthesized by thin-layer technique, and its crystal structure was obtained from X-ray powder diffraction data at room temperature. The structure of YPO4·2H2O was solved by direct methods and refined using the Rietveld analysis. The compound crystallizes in the monoclinic space group C2/c, with unit cell dimensions a = 6.15326(3), b = 14.99687(8), c = 5.57848(3) Å, β = 115.4319(4)º, V = 464.896(4) Å 3 , Z = 4. It has the gypsum-type crystal structure, with metal-phosphate 2D polymeric network, parallel to the ac plane. Water molecules, coordinated by the yttrium atoms, provide hydrogen bonding between the layers, resulting into a three-dimensional network. The crystal structure of YPO4·2H2O is compared with that of isotypic Y1-x(Gd,Dy,Er)xPO4·2H2O (x = 0.053), investigated earlier.

Monazite, rhabdophane, xenotime & churchite: Vibrational spectroscopy of gadolinium phosphate polymorphs

“…Finally, the churchite crystallizes in the gypsum structure type in the C2/c space group of the monoclinic system [34]. Each Gd atom is coordinated to 8 oxygen atoms, six being provided by the phosphate groups and two by water molecules, to form distorted square antiprisms.…”

“…Indeed, churchite bears two non-equivalent water molecules in its structure, one being strongly attached to the PO4 network and the other more loosely bound in the interlayer space [34,37].…”

Synthesis, Crystal Structure, and Enthalpies of Formation of Churchite-type REPO4·2H2O (RE = Gd to Lu) Materials

“…According to the literature, the churchite-type REPO 4 As is observed in Figure 1, the calculated XRD pattern matches well with the experimental powder XRD pattern which confirms that the as-synthesized churchite-type materials adopt the (Table 2). 9 Two of the four O-P-O bond angles are considerably lower than the ideal tetrahedral angle as a result of the participation of O atoms in the bidentate bonding with the erbium atom ( Table 2). 9…”

“…[1][2][3][4][5][6] RE phosphates are both compositionally and structurally diverse and occur in nature as and Y). [7][8][9][10] Among these minerals, monazite and xenotime minerals contain the highest weight percent of rare earth elements. In addition, they also contain a large amount of U and Th thereby making these minerals radioactive.…”

“…To the best of our knowledge, there has been only two structural studies reported on churchite-type materials. 9,10 Those were carried out on synthetic (YPO 4 • 2 H 2 O) and natural churchite (Y 1-x (Gd,Dy,Er) x PO 4 • 2 H 2 O) samples. 9,10 Both these studies have shown that the churchite materials adopt the gypsum structure (CaSO 4 • 2 H 2 O) and crystallize in the monoclinic system (space group: C2/c).…”