A plate-type theory is developed for the flexural-extensional vibratory response and static voltage deformation of heterogeneous piezoelectric circular transducer elements. Known results for homogeneous disks and bimorphs are shown to be special cases of the theory. Application is made to the design of simply supported metal-piezoceramic unimorph disks, and thin piezoceramic bimorph benders possessing metallic electrodes of non-negligible thickness.