Microstructural Evolution in Fast‐Heated Cordierite‐Based Glass‐Ceramic Glazes for Ceramic Tile

Abstract

The crystallization mechanism of α‐cordierite from a B2O3‐ and TiO2‐containing glass submitted to fast heating in the cordierite primary phase field of the CaO–MgO–Al2O3–SiO2 quaternary system was investigated. Addition of B2O3 to a SiO2‐rich glass suppressed the formation of μ‐cordierite. This suppression facilitated densification by viscous flow before crystallization. Powder X‐ray diffractometry, field‐emission electron scanning microscopy, and energy‐dispersive X‐ray analysis revealed that α‐cordierite nucleated directly from glass on the boundaries of original particles and was probably favored by TiO2, which acted as a nucleant. The growth kinetics of α‐cordierite crystals was fast, and the crystals seemed to grow by consuming glass directly from the growing interphase. The estimated amount of α‐cordierite in the glass heated at 1160°C was 69.5 wt%, as determined using the Alegre method. The final microstructure consisted of an arrangement of well‐shaped hexagonal prisms, with sizes <3 μm, immersed in a residual glassy phase. The feasibility to develop new glass‐ceramic glazes using the present and previous works is considered.

Effect of TiO2 on the mullite formation and mechanical properties of alumina porcelain

“…TiO 2 has been extensively studied as a nucleating agent used in several glassy systems for the purpose of controlling crystallization in the different crystalline phases. [17][18][19][20] However, as far as we know there is no detailed information describing the effect TiO 2 has on influencing the microstructure and mechanical properties of alumina porcelain bodies.…”

Effect of boron oxide on the microstructure of mullite-based glass-ceramic glazes for floor-tiles in the CaO–MgO–Al2O3–SiO2 system

“…[5][6][7][8][9][10] Glassceramics materials have been developed containing diopside or cordierite as single crystalline phase, by heating under controlled conditions glassy compositions located in the primary phase field of these crystalline phases. Obviously, to attain the ultimate features of those glass-ceramic glazes several additives were required to favor the crystallization process.…”

Effect of ZnO/MgO ratio on the crystallization and optical properties of spinel opaque glazes

“…Glass‐ceramic glazes are interesting materials that improve mechanical and optical properties of floor and wall tiles such as high chemical and abrasion resistance, high surface hardness and good coating capability for clay support . The firing cycles used in the manufacture of ceramic tiles are extremely rapid—usually less than 60 minutes—and the maximum firing temperature does not exceed 1200°C . Controlled crystallization process during fast‐firing guarantees adequate crystallinity as well as sufficient flow‐ability and maturing of glass‐ceramic glazes to provide a homogeneous microcrystalline structure …”