PREPARATION AND PROPERTIES OF SOL-GEL DERIVED NANOSTRUCTURED THIN CERAMIC LAYERS

Thin ceramic layers of two different compositions were deposited onto substrates from sols with controlled viscosities. First, mullite (3Al2 O3 x 2SiO2) layers were deposited onto SiC platelets with resulting th icknesses of up to 1 mum. By thermal treatment at up to 900-degrees-C, dense layers consisting of crystals of about 20 nm were obtained. The measured hardness and Young modulus of the mullite layers were higher than those of mullite ceramics with grain sizes in the micrometre ran ge. Uncoated SiC platelets were oxidized three times faster than mulli te-coated platelets. Second, thin PZT layers with composition near the morphotropic phase boundary (PbZr0.53Ti0.47O3) were deposited from so ls onto platinum-coated silicon wafers exhibiting at the crystallizati on temperature of less than 500-degrees-C, dense packaging of crystals 30 nm in diameter. Increasing the applied temperature up to 700-degre es-C led to crystal sizes of up to 70 nm. After this thermal annealing the layers exhibited a remanent polarization of 14 muC cm-2, a coerci ve force of 7 kV mm-1, epsilon(r) > 1000, and a resistance greater tha n 10 MOMEGA.