Abstract
The influence of the technological texture on the DC conductivity of an illitic clay and kaolin was studied. Textured samples were prepared by layering a wet plastic mass made from distilled water and clay.
Anisotropy of the samples was assessed by studying the DC conductivity and dimensional changes as functions of temperature in parallel and perpendicular directions to the basal planes of illite and kaolinite crystals. It was found that the shrinkage of the samples after firing is more significant in the direction perpendicular to the basal planes.
The DC conductivity both in the illitic clay and kaolin is higher parallel to the basal planes of illite or kaolinite crystals than perpendicular to them. In both materials, the dominant charge carriers are K+ and Na+ ions, complemented by H+ and OH- ions during the removal of the physically bound water and dehydroxylation.
The influence of the texture remains observable in the kaolin samples even after a high-temperature treatment (1200 degrees C), contrary to the illitic clay where this influence is suppressed by the high amount of the glassy phase (similar to 80 mass %) after the thermal treatment at temperatures above 1000 degrees C. Compared to the illitic clay, the influence of the technological texture on the DC conductivity of kaolin is more significant.