Formation of NdBa2Cu3O7-delta amorphous phase by combining aero-acoustic levitation and splat quenching

Small spherical samples (diameter approximately 2 mm) of NdBa2Cu3O7-delta ( Nd123) were fully melted in Ar gas flow in an aero-acoustic levitation devi ce and subsequently rapidly cooled by splat quenching. For samples quenched above the liquidus, the microstructual and x-ray-diffraction (XRD) observa tions suggested the existence of the amorphous phase with small quantities of the BaCuO2 and BaCu2Ox. The high-temperature XRD results indicated that the decomposition of the amorphous phase, probably assisted by atmospheric CO2 and H2O, led to formation of the BaCO3 phase at 400 degreesC and, subse quently, the Nd123 phase was formed by the solid diffusion above 800 degree sC. Another set of Nd123 samples was fully melted in O-2 gas flow, undercoo led while levitated, and then splat quenched at a temperature below the per itectic temperature (T-P). These samples possessed a microcrystalline micro structure of the Nd123 phase that was confirmed by XRD. This indicated that the Nd123 phase was solidified directly from the undercooled melt quenched below T-P.