Macroporous and nanosized ceramic films prepared by modified sol-gel method with PMMA microsphere templates

Macroporous ceramic thick films consisting of nanosized particles have been fabricated successfully by a modified sol-gel method employing polymethylmethacrylate (PMMA) microspheres as a template. PMMA microspheres with a uniform particle size (mean diameter: 870 nm) were first deposited on an oxidized silicon substrate. Precursor solutions of Ti(i-C3H7O)4 in isopropyl alcohol, SnCl22H2O in dehydrated ethanol and MgCl26H2O in a mixture of ethanol and ultra pure water permeated into the openings of the template layer in vacuo, and then was air-dried at room temperature. The composite layers were subjected to heat treatment at 500–600 °C in air in order to remove the core PMMA templates by thermal decomposition and then to oxidize the precursor frameworks. In the case of a macroporous SnO2 thick film, this heat treatment resulted in formation of a self-standing network of interconnected hollow SnO2 microspheres whose shell walls consisted of nanosized oxide particles about 40 nm in diameter.