Abstract
The influence of sintering temperature on the critical transition temperature,Tc,for MgB2 superconductor was investigated systematically with the aid of room temperatureRaman scattering measurements and Raman spectral fit analysis. The Ramanspectra for all samples can be fitted with one phonon peak coming from theE2g modeat the Γ point of the Brillouin zone and two peaks coming from sampling ofthe phonon density of states (PDOS) due to disorder. The enhancedE2g mode in the Raman spectra with increasing sintering temperatureshows gradual strengthening of the electron–phonon coupling (EPC) inMgB2, which is thereason why the Tc of samples increases with increasing sintering temperature. The strength ofelectron–E2g coupling isestimated to be about 2.0 ± 0.5, which is larger than the average strength of the coupling of electrons with all the phonon modes,∼1.23.The Tc dependence on the profiles of the PDOS peaks is described using the variation of the peaks’frequencies and linewidths in different samples.
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