Impedance Spectra During Solid‐State Powder Reactions of Oxide Superconductors

Complex impedance spectra over the frequency range of 5 Hz to 13 MHz were measured during the solid‐state reaction of La₂CuO₄ (with and without Sr doping) from the constituent oxides or carbonate (Sr). A single bulk arc was observed which could be modeled as a simple resistor‐capacitor network. The resistance falls continuously with time, spanning several orders of magnitude. Complex impedance measurements appear to be quite sensitive to small volume fractions of an electronically conductive product phase, especially during the early stages of solid‐state reaction. Impedance spectroscopy should therefore be a useful tool for the investigation of processing reactions in electronic ceramics.