Piezoelectric actuator, ultrasound element, ultrasound probe, ultrasound device, and electronic device

A piezoelectric actuator comprising:

• a substrate in which an opening is formed, the opening extending along a first direction in a plan view;
• a vibrating plate having a first surface and a second surface outwardly opposite to each other, the first surface closing the opening;
• a piezoelectric element provided, corresponding to the opening, at the second surface of the vibrating plate;
• a sealing plate disposed on the second surface of the vibrating plate;
• a suppression part configured to suppress a vibration of the vibrating plate, the suppression part being formed in the sealing plate, the suppression part being configured with a plurality of suppression walls extending along a second direction different from the first direction in the plan view, each of the plurality of suppression walls being sandwiched by two through-holes disposed in the sealing plate, each of the through-holes housing the piezoelectric element;
• a first wall protruding from a first position of the first surface into the opening along a third direction different from the first and second directions;
• and
• a second wall protruding from a second position of the first surface into the opening along the third direction, wherein
• in the piezoelectric element, a first electrode, a piezoelectric layer, and a second electrode are stacked in this order from a side of the second surface,
• when a portion where the first electrode, the piezoelectric layer, and the second electrode overlap each other is defined as an active part, the first wall and the second wall are provided to sandwich the active part in the plan view, and
• the second wall is different from the first wall at least in one of a width along the second direction, a length along the first direction, and a physical property with respect to materials of the first and second walls.