Influence of Complexing Agents on Properties of YBa 2 Cu 4 O 8 Superconductors Prepared by the Sol-Gel Method

Author: Kareiva A.   Bryntse I.   Karppinen M.   Niinisto L.  

Publisher: Academic Press

ISSN: 0022-4596

Source: Journal of Solid State Chemistry, Vol.121, Iss.2, 1996-02, pp. : 356-361

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Abstract

A systematic study of sol-gel technique synthesized YBa 2 Cu 4 O 8 (124) is presented using six different complexing agents: ascorbic acid, citric acid, 1,2-ethanediol, poly(vinyl alcohol), succinic acid, and tartaric acid. These complexing agents were found to influence significantly the characteristics of both the precursors and the product superconducting material, in particular the homogeneity. The 124 phase was formed by a solid state reaction at 780#°C in flowing oxygen after decomposition of the organic anions at lower temperature. The dried precursor gels and final products were characterized by thermogravimetry, X-ray powder diffraction, scanning and transmission electron microscopy, and magnetic susceptibility measurements. Syntheses using either 1,2-ethanediol or tartaric acid yielded monophasic YBa 2 Cu 4 O 8 powder, with the highest diamagnetic volume fractions and superconducting transition temperatures (onset) at 79-80 K.