PHYSICOCHEMICAL PROPERTIES OF SOL-GEL DERIVED LEAD SCANDIUM TANTALATE PB(SC0.5TA0.5)03 THIN-FILMS

Thin films of lead scandium tantalate Pb(SC0.5Tao.5)03 (PST) have been prepared by a novel sol-gel process. The process involves two deposition steps. In the first, layers of ScTaO4 are deposited by spin coating a solution of metallorganic compounds of scandium and tantalum. A film of lead oxide is deposited intermittently onto the surface using a solution of lead acetate, and the process repeated to obtain thicker films. After firing, the composite film, a transparent film of PST is obtained. The crystallographic and morphological properties of the films have been analysed by X-ray diffraction and SEM and elemental analyses determined using EPMA. The films' electrical properties have been measured against field and temperature, showing a strong induced pyroelectric response (3.8 x 10(-3)Cm-2K-1), peak permittivities of 4500 and low loss. A high material figure-of-merit (11 x 10(-5)Pa-1/2) was obtained. Results are presented which illustrate the relationships between the properties and the observed structure of the films, with the processing conditions. A possible mechanism for the formation of perovskite PST is outlined.