Synthesis and Rietveld refinements of new ceramics Sr₂CaFe₂WO₉ and Sr₂PbFe₂TeO₉ perovskites

Abstract

Ceramics of Sr2CaFe2WO9 and Sr2PbFe2TeO9 double perovskites have been prepared in polycrystalline form by solid-state technique, in the air. The crystalline structure was analyzed using X-ray powder diffraction (XRPD) at room temperature. Rietveld analysis of XRPD patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a = 5.5453(1) Å, c = 7.8389(1) Å for Sr2CaFe2WO9, and a = 5.5994(15) Å, c = 7.8979(30) Å for Sr2PbFe2TeO9. A certain degree of anti-site disordering of W and/or Te and Fe on the B –sites have been detected, indicating the presence of a partial amount of W and/or Te at Fe positions and vice versa.

Characterization and Rietveld refinements of new dense ceramics Ba3−xSrxTb3−xCexO9 (x = 1 and 1.5) perovskites

“…The refined crystal structures of BSTC are identified using Rietveld refinements. They exhibit higher densification and have perovskite structures with the general formula Ba 2 SrTb 2 CeO 9 and Ba 1.5 Sr 1.5 Tb 1.5 Ce 1.5 O 9 , similar to Sr 2 CaFe 2 WO 9 and Sr 2 PbFe 2 TeO 9 perovskites, respectively (El Hachmi et al ., 2018). Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrical measurements were employed to discuss the crystalline structure and valence states of rare-earth ions Ce and Tb.…”