Synthesis of REBa₂Cu₃O_7-∂ (RE=Nd, Eu, Gd) Nanoparticles by Wet-Mixing Method

The Nd_0.33Eu_0.33Gd_0.33Ba₂Cu₃O_7-∂ (NEG-123) nanoparticles have been successfully synthesized by wet-mixing method using HNO₃ as dissolving agent. The NEG-123 samples are divided into two which were treated differently. The first and second samples were mixed respectively, for one and 24 hours. All the samples were then calcined at 600°C for 3 hours, and sintered at relatively low temperature (750 to 900°C), each for 30 minutes. Samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Rietveld analysis shows the lattice parameter of a-axis decreases with the increasing sintering temperature from 750 to 900°C, while the lattice parameter of b and c-axes increases. Further, it was known based on the XRD analysis that the higher the sintering temperature, the greater the peak intensities and average crystal size. The NEG-123 samples with the average crystal size of hundreds nanometer exhibit paramagnetism, while those with average crystal size of ten nanometers demonstrate superparamagnetism at room temperature.