Effect of excess Er203 addition on the levitation force of ErBa2Cu307 superconductor / Faizatul Lela Jafar

The effect of excess Er203 additioti to superconducting ErBa2Oi307-s is reported. ErBa2Cu307-6 pellets were prepared using conventional solid-state synthesis with final sintering at 930 °C in air for 24 hours. Appropriate amounts of Erz03 (0 to 20 wt. %) was then added to ErBa2Cu3O7.fi foliowed by regrinding and repelletizing before partial melting for a duration of 30 minutes in flowing oxygen at 1100 °C. The partially melted samples were reground and repelletized before final sintering at 930 °C in air for 24 hours. Resistance versus temperature measurements shows superconductivity only for samples with 0, 10 and 20 wt, % Er2Ü3 with Tc onset between 89-92 K and Tc zero between 71-84 K. Magnetic levitation force (MLF) measurements at 77 K on the samples observed non-linear relation between MLF with the amount of Er2Ü3 addition. At a separation distance of 0.24 cm between magnet and superconductor, MLF for pure sample is 9.9 mN. For the same separation distance, MLF initially drops to 1.8 mN for 5 wt. % Er203 and then increases back gradually from 4.9 mN for 10 wt. % Er203 to a maximum of 21.2 mN for 20 wt. % Er203. X-ray powder diffraction analyses showed formation of Er2BaCuO^ (Er211) phase, which may act as flux pinning centers in the Er203-added samples. The experimental results were also discussed in relation to weight-loss analysis of the samples.