Liquid droplet jetting apparatus and piezoelectric actuator

A liquid droplet jetting apparatus configured to jet liquid droplets onto a medium, comprising:

• a channel unit having liquid channels including a nozzle and a pressure chamber communicating with the nozzle formed therein;
• a piezoelectric actuator disposed on the channel unit to cover the pressure chamber;
• and
• a drive unit configured to drive the piezoelectric actuator,
• wherein the piezoelectric actuator includes:
• a first piezoelectric layer and a second piezoelectric layer which are stacked in a thickness direction thereof, and which cover the pressure chamber;
• an inner electrode disposed between the first piezoelectric layer and the second piezoelectric layer, facing the pressure chamber;
• a first outer electrode disposed in an area facing the inner electrode, of a surface of the first piezoelectric layer on an opposite side of the second piezoelectric layer;
• a second outer electrode disposed in an area facing the inner electrode, of a surface of the second piezoelectric layer on an opposite side of the first piezoelectric layer;
• a first low-permittivity portion having a permittivity lower than a permittivity of the first piezoelectric layer, which is disposed between the inner electrode and the first piezoelectric layer or between the first outer electrode and the first piezoelectric layer, facing a central portion of the pressure chamber;
• and
• a second low-permittivity portion having a permittivity lower than a permittivity of the second piezoelectric layer, which is disposed between the inner electrode and the second piezoelectric layer or between the second outer electrode and the second piezoelectric layer, facing a portion near an outer edge of the central portion of the pressure chamber;
• and
• wherein the drive unit is configured to generate an electric potential difference between the inner electrode and the first outer electrode, and between the inner electrode and the second outer electrode.