Investigation on mechanical and thermal properties of MgAl2O4-Mg2TiO4 solid solutions with spinel-type structure

Magnesium aluminate (MA) spinel has shown potential as a refractory material under harsh environments, such as high temperatures and frequent temperature variations. However, understanding the mechanical and thermal properties of MA spinel is a key step towards further improvement of MA spinel refractory materials in high-temperature fields. The formation of solid solution represents a prominent strategy to improve mechanical and thermal properties. The present study develops novel (1-x)MgAl2O4-xMg2TiO4 (0≤ x ≤ 0.1) solid solutions by single-step reaction sintering method using light-burned magnesia, reactive alumina, and as-prepared Mg2TiO4 (M2T) powders. The effects of M2T content on the crystal structure, mechanical properties, and thermal properties of the MgAl2O4-Mg2TiO4 solid solutions (MATss) were studied. Based on XRD, TEM, and HRTEM results, MATss were highly crystallized with a cubic spinel structure. Besides, the M2T addition facilitated the flexural strength, hardness, and elastic modulus in the MA spinel. Among these solid solutions, the x = 0.08 sample exhibited the highest flexural strength, hardness, and elastic modulus of 219.47 MPa, 19.99 GPa, and 270.2 GPa, respectively. M2T additive played a solid-solution strengthening role, which enhanced the inherent resistance to microstructural damage. Additionally, the x = 0.08 sample had the highest thermal conductivity and thermal diffusivity of 12.45 W/(m·K) and 7.98 mm2/s, respectively. In comparison with pure MA spinel, the x = 0.08 sample showed a lower thermal expansion coefficient (8.63 × 10-6 K-1 at 1550 °C). These excellent mechanical properties and exceptional thermal behavior enabled its widespread application in refractory materials.