Optimization of the fabrication process for high trapped field MgB2 bulks

• Several bulk MgB2 samples were prepared by solid state reaction at various temperatures between 700 and 950 oC.
• SEM and x-ray diffraction indicated that single phase MgB2 bulks can be obtained at medium sintering temperatures.
• A proper processing temperature is also the key parameter to achieve high trapped fields.
• Samples of 20 mm in diameter and 7 mm thick, produced at 775 oC exhibited the trapped field of 1.50 T at 20 K.

The optimization of the sintering conditions of disk shaped bulk MgB2 superconductors with respect to the trapped field is described. Series of samples were prepared by varying the sintering temperatures between 700 and 950 °C. The temperature range was divided into three regions, namely the low (<750 °C), medium (<825 °C), and high (>850 °C) temperature region. Scanning electron microscopy and X-ray diffraction indicated that homogenous single phase MgB2 bulks were produced in the medium sintering temperature range. At this processing temperature range the highest trapped field was also achieved. Samples of 20 mm in diameter and 7 mm thick produced at 775 °C exhibited trapped field of 1.50 T at 20 K.