Intrinsic Electrical Conductivity of Silicate Glass Doped with Ruthenium Dioxide: Experimental Evidence
Abstract
It has been shown experimentally that lead–silicate glass of various compositions itself becomes electrically conductive due to the diffusion of Ru atoms during the firing process. Using energy‐dispersive spectroscopy and profiling of the spreading resistance R S and thermoEMF S on beveled samples, a close correlation between the ruthenium concentration and the distribution of specific resistance and thermoEMF has been shown. Changes of the Ru atoms concentration and the spreading resistance R S , as well as the thermopower S through the diffusion layer, obey a simple diffusion law (complementary error function), when the diffusion coefficient does not depend on the concentration of diffusing atoms. At a very low concentration of Ru atoms (near the glass‐diffusion layer boundary), the thermopower S reaches 5–7 mV K −1 , while at the glass–RuO 2 boundary (high concentration of Ru atoms) it is several μV K −1 . The calculated diffusion length under normal annealing conditions of thick‐film resistors (10 min at 1123 K) exceeds 100 μm, which is many times greater than the average distance (0.5–2 μm) between RuO 2 particles and confirms that the glass matrix becomes uniformly doped and conductive.