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Reaction and Fired‐Property Studies of Cordierite Compositions

1954; Wiley; Volume: 37; Issue: 12 Linguagem: Inglês

10.1111/j.1151-2916.1954.tb13995.x

1551-2916

R. S. Lamar, Maurice F. Warner,

Thermal and Kinetic Analysis

Ceramic bodies approaching the theoretical composition of cordierite were prepared from mixtures of talc and clay; talc, clay, and varying amounts of MgCO 3 ; talc, clay, and alumina; and prochlorite and clay. Additions of BaCO 3 and PbSiO, were made. Differential thermal analysis and X‐ray diffraction methods were used in reaction studies of each composition. Bodies had thermal expansions from 0.344 to 0.109% (25° to 900°C.). BaCO 3 and PbSiO 3 affected thermal expansion. Dielectric properties were improved by additions of BaCO 3 and were markedly improved by additions of both BaCO 3 and PbSiO l . Cordierite started to crystallize at about 1250°. Additions of PbSiO 3 lowered this temperature about 50°C. With sufficient BaCO 3 , the Ba‐C phase, as described by Wisely, crystallized in place of cordierite. The crystallization temperature for the Ba‐C phase was about 1200°C. With insufficient BaCO 3 , both cordierite and Ba‐C formed. Additions of PbSiO 3 reduced the crystallization temperature of the Ba‐C phase by 50°C. and increased the glassy phase. Several of the compositions should haw considerable practical value.