The spectroscopic performances of Schottky barrier diodes (SBDs) and bulk detectors fabricated on n-type epitaxial 4H-SiC and high-purity semi-insulating (HPSI) 4H-SiC substrates are studied using $\mathrm{241}$Am alpha-particles. The spectral responses of the SBD detectors reveal a good energy resolution of 55 keV FWHM ($\sim$1%) at −60 V, and $\sim$90% charge collection efficiency (CCE) at −100 V. The collected signal charge is stable with time in the SBD detectors; hence polarization effects are not noticed, indicating the good crystalline quality of the epitaxial 4H-SiC for detector applications. On the contrary, a poor energy resolution of 675 keV FWHM (12.3%) at −400 V and a maximum CCE of 28% at −500 V are obtained for the bulk detectors. Moreover, the CCE is found to decrease with time after the application of bias voltage implying the polarization phenomenon. Accordingly, the steady-state CCE of the bulk detectors at −500V is decreased to 13% from its initial value. The inferior spectral response of the bulk detectors is possibly due to the charge trapping and polarization effects. Furthermore, the neutron irradiation effects on the $\alpha$-particle spectral response of the detectors are examined up to a fluence of 10$11$ n/cm2. To study the reliability of the SBD detectors at higher irradiation levels, the 14.1 MeV neutron irradiation induced changes in the electrical characteristics of the SBD are investigated up to a fluence of $2\times 10^{15}$n/cm2 by device simulations and the probable degradation in the detector response is analyzed. Finally, the possibility of employing 4H-SiC detectors for the fusion alpha-particle diagnostics is discussed.