The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

• MgB2 was obtained by ex-situ spark plasma sintering for different heating rates.
• Heating rates were 20–475 °C/min: the optimum heating rate is ∼100 °C/min.
• For 100 °C/min, Jc0, Hirr and (Jc0 x μ0Hirr) have maximum values.
• For 100 °C/min, macro flux jumps are partially suppressed at 5 K.
• Grain boundaries are modified depending on the heating rate.

Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 °C/min were used. Samples have high density, above 95%. The onset critical temperature Tc, is about 38.8 K. There is an optimum heating rate of ∼100 °C/min to maximize the critical current density Jc0, the irreversibility field Hirr, the product (Jc0 x μ0Hirr), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries.