Microstructure and heat storage performance of TiO2 doped corundum-magnesium aluminate spinel composite ceramics

In this study, corundum-magnesium aluminate spinel (C-MAS) composite heat storage ceramics were synthesized by co-adding MgO and TiO2 to Al2O3. The effects of TiO2 and the Al2O3/MgO ratio on the heat storage performance were evaluated. The findings reveal that Ti4+ integrates into the corundum and MAS lattice, leading to lattice distortion and facilitating solid-phase reaction and MAS generation. Optimal performance is observed at an Al2O3/MgO ratio of 95:5, with dense structure, minimal pores, and uniform grain size, exhibiting exceptional thermal shock resistance. They withstand 30 thermal shocks (RT-1100 degrees C) with a 7.12 % increase in bending strength. Moreover, the addition of MgO and TiO2 significantly enhances the specific heat capacity, characterized by an average specific heat capacity of 1.06 J.g(-1).degrees C-1 and a heat storage density of 1443.83 kJ.kg(-1) (RT-1100 degrees C). TiO2 introduces additional point defects or alters existing ones in the Al2O3 matrix, increasing heat capacity through defect thermal motion. The formation of MAS leads to higher specific heat capacity, due to the greater degrees of freedom and complex lattice vibrations of the spinel structure. These properties position C-MAS composite ceramics as promising candidates for the heat storage materials of the new generation of solar thermal power generation.