Sol-gel synthesis and electrical characterization of (Pb,Ca)TiO3 thin films

Calcium modified lead titanate films have been prepared on Pt/Ti/SiO2/Si substrates using a sol-gel route. The sols were prepared from propanediol solutions of Pb(CH3COO)(2) . xH(2)O, Ti(OC3H7)(2)(CH3COCHCOCH3)(2) and Ca(NO3)(2) . xH(2)O. Tetragonal phase (Pb, Ca)TiO3 films could be produced by firing the coatings at 650 degrees C for 30 min. The limiting thickness of crack-free Single layers was similar to 0.4 mu m, but 3 mu m thick films could be made by a multiple deposition technique. Dielectric and ferroelectric parameters were determined for single layer 0.5 mu m films for compositions up to 30 mol % Ca. The average values of remanent polarization, P-r and coercive field, E(c) decreased with increasing Ca content from similar to 11 mu C cm(-2) and similar to 125 kV cm(-1) for a 10 mol % Ca composition to similar to 8 mu C cm(-2) and 80 kV cm(-1) for 30 mol % Ca films. It was noted that the statistical variation in electrical values across each film was greater than in PZT films made by a similar sol-gel route. Reasons for this are discussed in terms of the incidence of physical defects in the films.