Controlled cracking of multilayer ceramic bodies

Cracking of granular ceramic films during drying is a well-known phenomenon . Previous work has shown that films cast above a critical thickness on non porous substrates crack spontaneously. Films cast on previously cast layers crack at thicknesses that depend on the solids content of the slurry. Crac king occurs in this instance when films are cast above a critical saturatio n thickness (CST). The CST is defined as the thickness of granular material that would be 100% saturated by the liquid contained in the last cast laye r. The CST is remarkably similar in magnitude to the critical cracking thic kness obtained with similarly prepared slurries on dense substrates. For ex ample, 0.5 mu m Al2O3 slurries in water have a CST of 65 mu m when cast on previously deposited layers of Al2O3. Similarly prepared slurries crack spo ntaneously when cast on single-crystal silicon at any thickness above simil ar to 60 mu m.