Isomorphous substitution of europium for strontium in the structure of synthetic hydroxovanadate

Get’man, E. I.; Yablochkova, N. V.; Loboda, S. N.; Prisedsky, V. V.; Antonovich, V. P.; Chivireva, N. А.

doi:10.1016/j.jssc.2008.06.003

Cited by 20 publications

(10 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In this respect, substitution of RE elements in Pb-containing apatites behaves quite differently from that in calcium or strontium apatites. In the latter case, as in the systems Ca 10– x Ln x (PO 4 ) 6 (OH) 2– x O x or Sr 10– x Ln x (PO 4 ) 6 (OH) 2– x O x , the distances M2–M2 and M2–O4 decrease with the degree of substitution. ,− For instance, in Ca 10– x La x (PO 4 ) 6 (OH) 2– x O x , the Ca,La2–Ca,La2 length changes from 4.052(5) to 3.860(6) Å and Ca,La2–O4 from 2.380(3) to 2.240(4) Å, with x increasing from 0 to 0.80, in spite of the ionic radius of La (1.17 Å) being larger than that of Ca (1.14 Å). Such behavior is determined by an increased electrostatic interaction between cations in the triangle corners and O 2– anions in the channels opposite the triangle centers as a result of the replacement under the scheme Ca 2+ + OH – → La 3+ + O 2– .…”

Section: Resultsmentioning

confidence: 97%

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆

et al. 2016

View full text Add to dashboard Cite

The substitution of rare-earth elements (REEs) for Pb in the lacunary apatite Pb8Na2(PO4)6 with void structural channels was studied by means of powder X-ray diffraction (including the Rietveld refinement), scanning electron microscopy, energy-dispersive X-ray microanalysis, and IR spectroscopy and also measurements of the electrical conductivity. The substitution limits (xmax in Pb8-xLnxNa2(PO4)6Ox/2) at 800 °C were found to decrease with the atomic number of the REE from 1.40 for La to 0.12 for Yb with a rapid drop from light to heavy lanthanides (between Gd and Tb). The REE atoms substitute for Pb predominantly at Pb2 sites of the apatite structure according to the scheme 2Pb(2+) + □ → 2Ln(3+) + O(2-), where □ is a vacancy in the structural channel. The substitution in lacunary apatite produces quite different changes in the structural parameters compared with broadly studied alkaline-earth hydroxyapatites. In spite of the much lower ionic radii of REE than that of Pb(2+), the mean distances ⟨Pb1-O⟩ somewhat increase, whereas the distances ⟨Pb2-Pb2⟩ and ⟨Pb2-O4⟩ do not change considerably with the degree of substitution. This implies control of the substitution by not only spatial and charge accommodation of REE ions but also the availability of a stereochemically active 6s(2) electron pair on Pb(2+). The high-temperature electrical conductivity shows dependence on the degree of substitution with a minimum at x = 0.2 indicative of a possible change of the type of conductivity.

show abstract

Section: Resultsmentioning

confidence: 97%

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆

et al. 2016

View full text Add to dashboard Cite

show abstract

“…A similar dependence was observed also for REE-substituted strontium hydroxovanadate Sr 10-x REE x (VO 4 ) 6 (OH) 2-x O x . 58 3.2. IR Absorption Spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Isomorphous Substitutions of Rare Earth Elements for Calcium in Synthetic Hydroxyapatites

et al. 2010

View full text Add to dashboard Cite

Polycrystalline hydroxyapatites Ca(10-x)REE(x)(PO(4))(6)(OH)(2-x)O(x) were synthesized and studied by X-ray powder diffraction, infrared absorption, diffuse-reflectance spectroscopy, and thermogravimetry. The solubility limits x(max) of rare earth elements (REE) in Ca hydroxyapatites decreases with an increasing REE atomic number from x(max) = 2.00 for La, Pr, and Nd to x(max) = 0.20 for Yb at 1100 °C. Refinements of X-ray diffraction patterns by the Rietveld method show that REE atoms substitute for Ca preferentially at the Ca(2) sites of the apatite structure. The substitution decreases the Ca(2)-O(4) atomic distances in the calcium coordination polyhedra and increases the Ca(2)-O(1,2,3) distances. This observation shows that interatomic distances depend not only on radii of the ions involved in the substitution but also on their charges.

show abstract

“…They inferred the existence of H + outside the channel in oxyhydroxyapatites and provided possible atomic co-ordinates for a H atom in HAsO 2À 4 . Get'man et al [15] studied the possibility of isomorphous substitutions of Eu 3 + for Sr 2 + (Sr 2 + +OH 1 À -Eu 3 + +O 2 À ) in strontium hydroxovanadates and have shown that such replacement is possible within a wide range of Eu/Sr ratios. Formation of HSiO 4 groups in apatite structure was studied by Astala et al [16] and Arcos et al [17].…”

Section: Resultsmentioning

confidence: 99%

New bismuth calcium oxysilicate with apatite structure: Synthesis and structural characterization

Uvarov

Shenawi-Khalil

Popov

2010

Journal of Solid State Chemistry

View full text Add to dashboard Cite

Isomorphous substitution of europium for strontium in the structure of synthetic hydroxovanadate

Cited by 20 publications

References 16 publications

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆

Isomorphous Substitutions of Rare Earth Elements for Calcium in Synthetic Hydroxyapatites

New bismuth calcium oxysilicate with apatite structure: Synthesis and structural characterization

Contact Info

Product

Resources

About

Isomorphous substitution of europium for strontium in the structure of synthetic hydroxovanadate

Cited by 20 publications

References 16 publications

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb8Na2(PO4)6

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb8Na2(PO4)6

Isomorphous Substitutions of Rare Earth Elements for Calcium in Synthetic Hydroxyapatites

New bismuth calcium oxysilicate with apatite structure: Synthesis and structural characterization

Contact Info

Product

Resources

About

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆

Isomorphous Substitution of Rare-Earth Elements in Lacunary Apatite Pb₈Na₂(PO₄)₆