Development of a novel synthetic route to produce ceramic oxide superconductors, the xerogel method
The scope of this work was to explore new chemical synthetic techniques to prepare ceramic superconductors with the goals: (1) optimization of the final products characteristics, such as phase purity and particle size; (2) atomic level mixing of the precursors; (3) stability of the precursors under a variety of atmospheric conditions; (4) avoidance of phase separation; and (5) generalization of the technique. This work reports the development of a technique that comprises the use of organic gelling agents to gel a solution of the metal salts required to obtain the final ceramic. This gel is dried to obtain a zerogel. The method has been successfully used to prepare high purity ceramic superconductors such as: YBa[sub 2]Cu[sub 3]O[sub 7], YBa[sub 2]Cu[sub 4]O[sub 8], Bi[sub 2]Sr[sub 2]Ca[sub 1]Cu[sub 2]O[sub 8] and Pb[sub x]Bi[sub 2[minus]x]Sr[sub 2]Ca[sub 2]-Cu[sub 3]O[sub 10]. Other ceramic materials were also prepared. The choice of gelling agents was made accounting for ash residue after calcination and pH of the solution to be gelled. Inherent problems dealing with solubility of some of the originals salts or metals were overcome using lateral research. The precursors and final materials were characterized for chemical and phase purity, particle size, and morphology. Thermal analysis was used to determine optimal heat treatments and in some specific cases (YBa[sub 2]Cu[sub 4]O[sub 8]) as an additional test for products quality. Physical characteristics such as resistivity and magnetic susceptibility found to be better compariable to those achieved by other processes. The heat treatment conditions of the materials were improved by shortening of the treatment times and/or decreasing the treatment temperatures and pressures. Although these results and diffraction patterns of the precursors indicated mixing at the atomic level, other experiments proved the absence of such an atomic mixture and indicated the presence of a homogeneous mixture at the nanometer level.
- Research Organization:
- Temple Univ., Philadelphia, PA (United States)
- OSTI ID:
- 7207499
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALLOYS
CERAMICS
CHEMICAL PREPARATION
COPPER COMPOUNDS
CUPRATES
HEAT TREATMENTS
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SOL-GEL PROCESS
STRUCTURAL CHEMICAL ANALYSIS
SUPERCONDUCTORS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS