Synthesis of reactive ceramic powders by the citrate technique

摘要

The citrate technique has been used to produce homogeneous, fine and reactive ceramic powders. That technique consists basically in preparing polymeric resins by adding citric acid and polyethylene glycol to liquid solutions of the inorganic ceramic precursors, followed by controlled stirring and heating. High density bodies are then obtained after conformation and sintering the powders that resulted from the calcination of the resins. ZrO_2:MgO, ZrO_2:La_2O_3 and ThO_2:Y_2O_3 solid electrolytes to be used as electrochemical transducers in oxygen sensors, and Ag-YBa_2Cu_3O_(7-x) composite high-T_c superconductors were obtained by that technique. The powders have been analyzed by sedimentation and gas adsorption techniques for determining particle size distribution, X-ray diffractometry for structural phase content, and Scanning and Transmission Electron Microscopy (SEM and TEM) for observation of particle agglomeration. The sintered solid electrolyte ceramic pellets, have been analyzed by XRD, by SEM for grain morphology, and Impedance Spectroscopy for bulk and grain boundary electrical characterization; the composite superconductor have been characterized by optical microscopy, XRD and four-probe electrical resistivity measurements.