Crystallization and microstructural evolution of cordierite-based thick film dielectrics

Microstructural evolution of glass-ceramic dielectric thick films based on a nonstoichiometric cordierite, 2.4MgO . 2Al(2)O(3). 5SiO(2), containing B2 O3, P2O5, and PbO were investigated in conjunction with nucleation and crys tal growth. The cordierite thick films were deposited by screen printing on a 96% alumina substrate, and then fired in the temperature range of 850-95 0 degrees C in a N-2 atmosphere. Surface microstructure characteristics of the thick films depended on PbO content. Heterogeneous nucleation originate d predominantly from the interface between the densified thick film and the alumina substrate. The added PbO segregated to the remaining glass during crystallization, and the relative concentration of Pb in the glass was prov en to increase with rising temperature. Most of the remaining glass protrud ed from the him surface at the final temperature of 950 degrees C. Penetrat ion of the alumina substrate by the remaining glass was also observed. The influences of temperature and PbO on the microstructural evolution includin g nucleation and growth will be discussed with possible explanations for th e observed results. (C) 1998 Acta Metallurgica Inc. Published by Elsevier S cience Ltd. All rights reserved.