Small polaron hopping conduction mechanism in Mg-doped LaMnO3 ceramics

The cold sintering process (CSP) is frequently applied for the fabrication of ceramics with a low melting point and sintering temperature. However, the effect of CSP on electrical performance in LaMnO3-based ceramics has seldom been explored. In this paper, the LaMg0.5Mn0.5O3 ceramics were prepared using both CSP and conventional sintering (CS) for comparison. X-ray diffraction results demonstrated that both the CSP and CS ceramics consist of the LaMnO3 phase and the MgMn2O4 phase. To investigate the relationship between temperature and electrical performance, the small polaron hopping (SPH) and Mott variable range hopping (Mott-VRH) conductivity mechanisms were employed. Notably, the CSP ceramic exhibits a high SPH mechanism fitted linearity (R-squared value = 99.90%) in a wide temperature range from 198 to 1273 K. In contrast, while the CS ceramic also exhibits high linearity (R-squared value = 99.98%) in the high-temperature range (473–1273 K), it deviates from this behavior at lower temperatures. Considering the phase transition process, the Jahn–Teller effect, and the high Mn3+ content (91.21%), the MgMn2O4 secondary phase appears to play a crucial role in the properties.