Preparation of high-purity Tl-based ‘‘1223’’ superconductor phase by modified Pechini process in water solution

Abstract

Because of the mixed metal valance state of thallium in a Tl-based superconductor, a nearly single ‘‘1223’’ phase can be readily prepared by a modified Pechini method (US Patent 3 330 697). Tl2O3 and other metal nitrates are dissolved in an aqueous solution plus a certain amount of oxalic acid for chelating the metal cations. The desired phase shows zero resistance at 114 K and the phase purity is identified by x-ray diffraction. Characteristics of superconductivity also are evidenced by the Meissner effect. The preparation technique is considered valuable to purify multiphase superconductors for mass production.

Theoretical investigation of geometric configurations and vibrational spectra in citric acid complexes

“…A deeper understanding of complexes between α-hydroxycarboxylic acids and metals (M) that are formed on those routes is desirable, since these compounds are highly effective in obtaining heterometallic advanced ceramics 1 . Several metallic ions with different applications have been employed in this kind of route, such as lithium ion in the manufacturing of cathodes for fuel cells 2,3 and barium ion in pellets of high temperature superconductors [4][5][6] , magnetic materials 7,8 , and multiferroic materials 9 . The modified polymeric precursors method (MPPM) 1,4 involves the polyesterification process of a metal chelate complex using a hydroxycarboxylic acid and a polyhydroxy alcohol in an aqueous solution, which turns into a polymeric gel.…”

“…The modified polymeric precursors method (MPPM) 1,4 involves the polyesterification process of a metal chelate complex using a hydroxycarboxylic acid and a polyhydroxy alcohol in an aqueous solution, which turns into a polymeric gel. In this method, the most commonly employed carboxylic acid is citric acid (CA) 4 . The MPPM method has been widely used, since it allows for the preparation of polycrystalline samples of excellent quality, obtaining a highly homogeneous ceramic powder with nanometer-scale particles, and it is reactive at temperatures up to 30% lower than the ceramic powders obtained by traditional routes 1,5 .…”

Modified Pechini Synthesis of Oxide Powders and Thin Films

“…Focus on reducing the amounts of organics occurred in the following years and water was introduced as a solvent for the precursors. One of the first publications using the water based approach was a study of superconducting film formation (Chiang et al 1991). The term "modified Pechini process" is today mostly used for a process were aqueous solutions are used as precursors and this can be defined in the following way: The modified Pechini type of synthesis process to oxide materials starts with a homogeneous aqueous solution containing the desired cation precursors in stoichiometric ratio and selected additives, which by evaporation and reactions is converted to a rigid cross-linked polymer hindering segregation of the cations.…”

Synthesis of Nano‐γ‐Ferric Oxide by Thermolysis of the 2‐Mercapto‐5‐Methylpyridine‐N‐Oxide‐Iron(III) Complex via Factorial Design

“…The Design of Experiments (DOE) was performed to satisfy 2 2 fractional design [24] with four duplicate experiments in two levels, low (-) and high (+). The optimum combination of levels of factors A (thermolysis temperature) and B (thermolysis time) for the lowest magnitude of particle mean size were investigated.…”