The present disclosure is of a bone conduction sound transmission device. The bone conduction sound transmission device includes of a laminated structure and a base structure. The laminated structure is formed by a vibration unit and an acoustic transducer unit. The base structure is configured to load the laminated structure. At least one side of the laminated structure is physically connected to the base structure. The base structure vibrates based on an external vibration signal, and the vibration unit deforms in response to the vibration of the base structure; and the acoustic transducer unit generates an electrical signal based on the deformation of the vibration unit.

A hollow three-dimensional piezoelectric device of conformable tape-casted textured ceramic material is formed sheets that are pre-cut in preselected patterns and smoothly conformably stacked in layers on a mold defining the desired three-dimensional shape. The final stack is isostatically compressed into the shape of the mold. The predetermined cut patterns are selectively configured to facilitate the smoothly conformable placement and stacking of the layers over the entire mold surface. The cut pattern may be three, four, or more convex circular triangles extending radially from a common point and that fit together to form a hemisphere when conformed to the mold. Each layer may comprise one or a plurality of tape-casted sheets, and the cut patterns in successive layers may be gradually dimensionally increased to accommodate the layer-to-layer increase in the diameter (i.e., thickness) of the stack.

A liquid ejecting head includes, stacked in this order from a lower side to an upper side along a stacking direction intersecting an arrangement direction and an extending direction intersecting the arrangement direction: a pressure chamber substrate, a diaphragm, a first common electrode, a first thin film piezoelectric body, a first individual electrode, an insulating layer, a second individual electrode, a second thin film piezoelectric layer, and a second common electrode. The first and second individual electrodes are blocked by the insulating layer in a region where the first and second individual electrodes overlap the pressure chamber when viewed in the stacking direction.

In a piezoelectric element in which a lower electrode, a piezoelectric layer formed of a perovskite-type complex oxide, and an upper electrode are laminated in a laminating direction, the upper electrode has a first hydrogen absorbing layer that absorbs hydrogen. The upper electrode of the piezoelectric element preferably has a second hydrogen absorbing layer different from the first hydrogen absorbing layer. In the piezoelectric element, the film thickness of the first hydrogen absorbing layer is preferably thicker than the film thickness of the second hydrogen absorbing layer in the laminating direction.