SYNTHESIS, STRUCTURE, AND XPS CHARACTERIZATION OF THE STOICHIOMETRIC PHASE SR2CUO2F2

Citation
Jl. Kissick et al., SYNTHESIS, STRUCTURE, AND XPS CHARACTERIZATION OF THE STOICHIOMETRIC PHASE SR2CUO2F2, Physical review. B, Condensed matter, 56(5), 1997, pp. 2831-2835
Citations number
20
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
56
Issue
5
Year of publication
1997
Pages
2831 - 2835
Database
ISI
SICI code
0163-1829(1997)56:5<2831:SSAXCO>2.0.ZU;2-I
Abstract
Thermogravimetric analysis has revealed that reduction of Sr2CuO2F2+de lta in 10% H-2/90% N-2, occurs in two distinct steps on heating up to 930 degrees C. Whereas reduction to give SrF2, SrO, and Cu is complete above 800 degrees C, a stable intermediate forms in the region betwee n 250 and 450 degrees C. This has been identified as a new tetragonal (I4/mmm) phase, Sr2CuO2F2, with unit-cell dimensions a = 3.967(1) Angs trom and c = 12.816(2) Angstrom. The structure has been determined fro m powder x-ray-diffraction data and is related to Nd2CuO4 (T'-type). M adelung energy, bond valence sum calculations, and F 1s-XPS data clear ly indicate that the F- ions occupy sites within the fluorite block (S r2F2) insulating layers. This contrasts with the La2CuO4 (T-type) stru cture which is adopted by Sr2CuO2F2+delta.