Sintering of BaTiO3 powder/sol composite thick films and their dielectric and piezoelectric properties
Résumé
In this work, barium titanate thick films are produced at low-temperature using a modified sol–gel/ceramic powder technology named the composite route. In this process, a commercial BaTiO3 powder, doped or not by Li2O as sintering aid, is mixed with a stabilized titanium (IV) isopropoxide/barium acetate sol to obtain a composite ink. Two sols, using different solvents and chelating agents, are tested. Characterization of the evolution of theses sols with an increase in temperature is realized by thermal analyses (TGA and DTA) and X-ray diffraction. The four type of inks obtained are screen-printed on metallized alumina substrates and sintered. Microstructures and electrical properties of the sintered composite films are compared to those processed from a conventional ink obtained by dispersing the barium titanate powder in an organic vehicle. Measurements of dielectric/piezoelectric properties highlight higher charge coefficients d33 for composite thick films (69 vs. 45 pC/N for conventional thick films at close thickness values) despite a lower relative permittivity (340 vs. 658) certainly due to the presence of a single domain BaTiO3 nano-crystallites.