Synthesis and characterization of β-Yb2Si2O7 powders

beta-Yb2Si2O7 powders were synthesized by a sol-gel method using ytterbium nitrate and tetraethyl orthosilicate as starting materials. The thermal history, influence of composition and calcining temperature on phase evolution of the gel were investigated using TG-DTA, FTIR and X-ray diffraction. Amorphous Yb2Si2O7 formed below 950 degrees C and a low-temperature phase (alpha-Yb2Si2O7) was detected in powders calcined at 1000 degrees C and 1100 degrees C. Well crystalline beta-Yb2Si2O7 powders were obtained after calcining the xerogel at 1200 degrees C for 2 h. The average particle size of the powders calcined at 1200 degrees C was similar to 300 nm. The crystallite size determined from both TEM and FWHM of XRD reflections was similar to 60 nm. Lattice parameters of beta-Yb2Si2O7 determined by Rietveld method were a=6.80053 angstrom, b=8.87508 angstrom, c=4.70740 angstrom and beta=101.984 degrees. Atomic positions of beta-Yb2Si2O7 were identified as Yb(0.5, 0.80548, 0),Si(0.74150, 0.5, 0.42936), O(1) (0.5, 0.5, 0.5), O(2) (0.89831, 0.5, 0.75248), O(3) (0.74229, 0.65022, 0.18086). (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.