Electrical properties of chemically derived (Pb,La)TiO3 thin films

Ferroelectric lead lanthanum titanate (PLT) thin films with compositions varying from pure PbTiO₃ to PLT 25/100 (0 to 25 mol.% La) were prepared by spin-casting 0.25 M solutions containing metallo-organic precursors of Pb, La and Ti. The as-deposited amorphous films were crystallized into the perovskite structure by heat treatment at temperatures between 450 and 650°C. Dielectric and ferroelectric properties of the thin (410-nm) films were characterized. The dielectric constants of the films varied from ~80 to ~690 for La contents varying from 0 to 25 mol.%, respectively. Dissipation factors varied from ~0.03 to ~0.09 over the same compositional range. Also studied was the temperature dependence of the dielectric properties in order to determine the effects of La content on the Curie point (T_c ). It is as found that T_c decreased with increasing La concentration. Coercive field and remanent polarization also decreased with increased La concentration. Hysteresis loops became slim and more symmetric with increasing La content