Modification of low-melting phase monticellite (CMS) by La2O3

Monticellite (CMS) refers to a silicate phase that exhibits the worst refractoriness, whereas it exists widely in magnesia refractories, such that the high temperature performance of magnesia refractories is seriously reduced. Given the above-described problem, CaLa4(SiO4)3O was fabricated in this study, and the effect of La2O3 addition on modification and microstructure evolution of low-melting phase monticellite (CMS) was investigated. As indicated by the results, La2O3 reacted with SiO2 and CaO to directly synthesize CaLa4(SiO4)3O while modifying and transforming the existing CMS into the high-melting-point phase CaLa4(SiO4)3O for its higher activity, such that the content of CMS in the system was significantly reduced. Besides, CaLa4(SiO4)3O grains exhibited a hollow tubular to club-shaped morphology by controlling the addition of La2O3. On that basis, contributing to the microstructure of form CaLa4(SiO4)3O grains interlocking and enveloping the low-melting phases inside after heating at 1400 °C. It is noteworthy that the CaLa4(SiO4)3O test cone had no softening and bending during the refractoriness test (the highest test temperature was 1800 °C), thus confirming CaLa4(SiO4)3O as a high-melting-point phase.