Effects of La2O3 on sintering of MgO-CaO ceramics: Molecular dynamic simulation and experiments

Abstract

The mechanism of the additive La₂O₃ on the sintering process of MgO-CaO ceramics was investigated by molecular dynamics simulation, and the interfacial reaction and nanoparticles sintering models were established. The simulations demonstrated that MgO and CaO dissolve into La₂O₃ crystals, creating O^2- vacancies around Mg²⁺ and Ca²⁺. These vacancies significantly increase the diffusion rate of ions. Meanwhile, the La₂O₃ shifts the sintering driving force from reducing internal energy to increasing entropy, thereby enhancing the sintering degree of nanoparticles. However, excessive La₂O₃ introduction prolongs solid solution reaction times and impedes particle-particle contact, negatively affecting sintering densification. Experimental results show that the density of MgO-CaO ceramics initially increases with the addition of La₂O₃, reaching a peak of 3.43 g/cm³ at 0.3 mol%, before decreasing. This result aligns with the model's predictions regarding the effect of La₂O₃ addition. Moreover, the established models offer reference for selecting sintering aids in composite ceramics production.