a1 Istituto Nazionale per la Fisica della Materia (INFM) and Department of Physics, University of Modena, 41100 Modena, Italy
a2 Department of Earth Sciences, University of Modena, 41100 Modena, Italy
This paper deals with the mechanisms and kinetics of interactions between screen printed and fired PbO layers and ceramic substrates: alumina and beryllia. The interaction with alumina occurs via two main processes: (i) a reaction between PbO and Al2O3 grains, which induces the formation of a crystalline phase, Pb2Al2O5; and (ii) an interdiffusion process involving Pb and the intergranular amorphous phase in the ceramic substrate. This latter process results in a compositional change of the intergranular phase at considerable depths inside the ceramic substrate, as well as in the formation of a high lead glass layer on the substrate surface. Since PbO is not completely reacted, the Pb penetration in the ceramic is diffusion limited (penetration depth , where td is the reaction time) with an activation energy of 1.20 ± 0.05 eV. The ceramic microstructure significantly affects the interaction processes.
(Received July 01 1996)
(Accepted August 22 1996)
a) Now with CMBM (Centre of Medical Biophysics and Materials), Povo, Trento, Italy.