A PZT-type material, doped with niobium and lithium was prepared by the ceramic technique. The microstructure of the sintered material at 1280 degrees C was performed by scanning electron microscopy (SEM), transmission electron microscopy and by X-ray diffraction. Dielectric and piezoelectric properties were measured. The good planar properties of the material made it possible to obtain ceramic disks with a strong radial mode. Two such disks, glued together, with opposed polarisation constitute a bimorf element, which successfully converts the radial mode into a flexural one. At the center of the bimorf a conical acoustical impedance adapter is fixed in order to increase the frontal acoustical emission of the device. This ultrasonic device provides a broad band, high acoustical emission, and is suitable to work as a high efficiency ultrasonic siren. It can be used in intruder alarm devices, ultrasonic telemeters.