Sol-Gel Synthesis, X-Ray Diffraction Studies and Electric Conductivity of Sodium Europium Silicate

Sodium europium silicate, NaEu9(SiO4)6O2, with apatite structure has been obtained and studied using X-ray diffraction and SEM. It has been shown that sodium sublimation does not take place upon synthesis by the sol-gel method. Rietveld refinement has revealed that sodium atoms are ordered and occupy the 4f position. O(4) atoms not related to silicate ions are placed at the centers of Eu(2) triangles. DC and AC electric conductivity and activation energy have been determined for the compound studied

Synthesis, Crystal Structure Refinement, and Electrical Conductivity of Pb(8−x)Na2Smx(VO4)6O(x/2)

Solid solutions of Pb(8−x)Na2Smx(VO4)6O(x/2) were studied using X-ray diffraction analysis including Rietveld refinement and scanning electron microscopy and by measuring their electrical conductivity. Crystal structure of the solid solutions was refined and the solubility region 0 ≤ x ≤ 0.2 was determined for samarium substitution for lead under the scheme 2Pb2+ + ◻ → 2Sm3+ + O2-. The influence of degree of substitution on the electrical conductivity of solid solutions was established

Sol-Gel Synthesis, X-Ray Diffraction Studies and Electric Conductivity of Sodium Europium Silicate

Sodium europium silicate, NaEu9(SiO4)6O2, with apatite structure has been obtained and studied using X-ray diffraction and SEM. It has been shown that sodium sublimation does not take place upon synthesis by the sol-gel method. Rietveld refinement has revealed that sodium atoms are ordered and occupy the 4f position. O(4) atoms not related to silicate ions are placed at the centers of Eu(2) triangles. DC and AC electric conductivity and activation energy have been determined for the compound studied

Synthesis, characterization and electrical properties of Pb(8-x)Na2Ndx(Vo4)6O(x/2) solid solutions

Substitution of neodymium for lead in the apatite structure in accordance to scheme 2Pb2+□ → 2No3+ + O2- has been investigated by X-ray powder diffraction, scanning electron microscopy, IR spectroscopy and the measurement of electrical conductivity. It was estimated that single phase solid solutions Pb(8-x)Na2Ndx(VO4)6O(x/2) are formed in the range of x - 0-0.25. The crystal structure features of some samples have been refined by the Rietveld method. It was shown that ions Nd3+ preferably occupy M(1) site. Influence of the composition x on the electrical conductivity and activation energy has been investigated

Sol-Gel Synthesis, X-Ray Diffraction Studies, and Electric Conductivity of Sodium Europium Silicate

Sodium europium silicate, NaEu9(SiO4)6O2, with apatite structure has been obtained and studied using X-ray diffraction and SEM. It has been shown that sodium sublimation does not take place upon synthesis by the sol-gel method. Rietveld refinement has revealed that sodium atoms are ordered and occupy the 4f position. O(4) atoms not related to silicate ions are placed at the centers of Eu(2) triangles. DC and AC electric conductivity and activation energy have been determined for the compound studied

Isomorphous Substitutions of Rare Earth Elements for Calcium in Synthetic Hydroxyapatites

Polycrystalline hydroxyapatites Ca10−xREEx(PO4)6(OH)2−xOx were synthesized and studied by X-ray powder diffraction, infrared absorption, diffuse-reflectance spectroscopy, and thermogravimetry. The solubility limits xmax of rare earth elements (REE) in Ca hydroxyapatites decreases with an increasing REE atomic number from xmax = 2.00 for La, Pr, and Nd to xmax = 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