A piezoelectric vibration element comprises a vibration element part 1, a vibration propagation part 2 made of a same material with a greater thickness than the vibration element part 1, a groove 6 disposed in the boundary of the vibration element part 1 and vibration propagation part 2, excitation electrodes 3 confronting the face side and back side of the vibration element part 1, a connection electrode 4 disposed in the vibration propagation part 2, and an external lead-out electrode 5 connected electrically to the connection electrode 4. In this piezoelectric vibration element, the main vibration is the overtone mode, that is, when the lowest order wave mode is first-order or second-order, the wavelength in the thickness direction is (2n+1) times (n being a natural number) thereof.

A bistable actuator for residual-current devices, including a lamina having at least one face, a first end, and a second end, and configured to actuate from a first stable position to a second stable position; at least one layer of piezoelectric material provided on the at least one face of the lamina at the first end of the lamina, and configured to stimulate the lamina to shift from the first stable position to the second stable position in response to an electrical activation signal; and a support element including an interlock coupling, and configured to support the first end and the second end of the lamina, wherein the interlock coupling is configured to interlock the first end of the lamina to the support element, and the second end of the lamina is rigidly coupled to the support element in order to keep the lamina in the first stable position.