c-Axis oriented sol-gel (Pb,Ca)TiO3 ferroelectric thin films on Pt MgO

Ca-modified lead titanate thin films were prepared on (111)Pt/(100)MgO substrates by spin-on sol-gel process. Two layers of 0.3 mol/l solution were deposited on the substrate and each of them subjected to drying and rapid thermal processing (RTP) for crystallization, which reduces tensile strains. Single perovskite films with a preferred orientation in the direction perpendicular to the plane of the substrate were obtained as measured by X-ray diffraction analysis. Pyroelectricity of these films was measured before and after a polarization process being the pyroelectric coefficient close to approximate to 2.5 x 10(-8) C cm(-2) K-1. Ferroelectric properties were also measured, obtaining values of P-R of approximate to 25 mu C cm(-2) and E-c of approximate to 110 kV.cm(-1). Compressive strains resulting from the differences between thermal expansion coefficients of the substrate and the film cause the (001) orientation of the (Pb,Ca)TiO3 perovskite layer, that is very convenient for pyroelectric devices. (C) 1999 Elsevier Science S.A. All rights reserved.