Calcium modified lead titanate thin films for electromechanical applications

Electromechanical properties of Pb1-xCaxTiO3 (PCT) thin films prepared by s ol-gel technique are investigated as a function of Ca content. Crystallizat ion of a perovskite phase is observed for the films subjected to the rapid thermal anneal at 650 degrees C. A small amount of pyrochlore phase is foun d for low Ca concentration (x=0.08). Tetragonality of the films is graduall y decreased with Ca addition in qualitative agreement with hulk ceramics da ta. Piezoelectric coefficient, d(33), measured by optical interferometry in itially increases with Ca content reaching a maximum at x=0.24. At this con centration, d33 of 70 pm/V is observed which matches well the value for hul k PCT ceramics. The strain developed at 400 kV/cm is progressively decrease d with Ca reflecting a decrease in tetragonality of the films. The observed difference in piezoelectric coefficients of PCT films and bulk ceramics is qualitatively explained by the clamping effect of the substrate and by dep oling of the films due to the influence of depolarizing field.