Microwave-assisted synthesis and critical analysis for YBa2Cu3O6+δ nanoparticles

A new cost effective scheme of a microwave-assisted sol-gel route followed by a short annealing time is proposed to synthesize YBCO nanoparticles (NPs) of various sizes. The advanced techniques of synchrotron radiation x-ray diffraction (SRXRD) and electron spin resonance (ESR) are used to analyze the size effects on their magnetic/superconducting properties. The major interesting finding is that the size of YBCO NPs could confine the amount of oxygen content and consequently change the superconducting transition temperature (TC) of YBCO NPs. The ESR result demonstrates a sensitive probe to characterize surface defects in the oxygen-deficient YBCO NPs.