J. Phys. IV France 08 (1998) Pr9-155-Pr9-158
Pyroelectric properties of sol-gel processed lanthanum modified lead titanate ferroelectric thin filmsM. Algueró, M.L. Calzada and L. Pardo
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain
Textured lanthanum modified lead titanate ferroelectric thin films have been prepared on Pt/Si substrates by a diol-based sol-gel procedure. Precursor solutions including a growing excess of PbO, and crystallization with a heating rate higher than 500°C min-1, are used. Pb/Ti ratio in films is measured by EDXS, and is found to increase systematically with the excess of PbO included in solutions. Such increase inPb/Ti is likely related to the disappearance of a Pb deficient second phase, reaching the nominal value of the perovskite in those films prepared from solutions including a 20% excess of PbO. Films dieletric constant, ε, remanent polarization, PR, and pyroelectric coefficient, γ, measured in poled samples, increase as the Pb/Ti ratio, reaching values of~730, ~25 µC cm-2 and ~1.4x10-2 µC cm-2K-1 in those with the nominal ratio of the perovskite. Infrared sensor figures of merit for voltage responsivity, Fv α γ/ε, and specific detectivity, Fm α γ/(ε)1/2, are calculated. The possibility of using films containing small amounts of second phase, with a smaller pyroelectric coefficient, but with a smaller dielectric constant, is discussed.
© EDP Sciences 1998