Multi-layer piezoelectric element

A multi-layer piezoelectric element comprising a stack formed by stacking piezoelectric layers and internal electrodes alternately one on another and external electrodes formed on a first side face and on a second side face of the stack, one of the adjacent internal electrodes being connected to the external electrode formed on the first side face and the other internal electrode being connected to the external electrode formed on the second side face,

• wherein the external electrodes include an electrically conductive material and glass, the external electrodes being formed from a porous electrically conductive material that has a three-dimensional mesh structure.

A multi-layer piezoelectric element comprising a stack formed by stacking piezoelectric layers and internal electrodes alternately one on another and external electrodes formed on a first side face and on a second side face of the stack, one of the adjacent internal electrodes being connected to the external electrode formed on the first side face and the other internal electrode being connected to the external electrode formed on the second side face,

• wherein the internal electrodes and the external electrodes include silver, and
• wherein the proportions of silver in the internal electrodes and in the external electrodes are set so that the ratio of silver content X (% by weight) to the entire electrically conductive material included in the internal electrode and the ratio of silver content Y (% by weight) to the total weight of the electrically conductive material and glass included in the external electrodes satisfy conditions of X≧85 and 0.9≦X/Y≦1.1.

A multi-layer piezoelectric element comprising a stack formed by stacking piezoelectric layers and internal electrodes alternately one on another and external electrodes formed on a first side face and on a second side face of the stack, one of the adjacent internal electrodes being connected to the external electrode formed on the first side face and the other internal electrode being connected to the external electrode formed on the second side face, the internal electrodes being made of an electrically conductive material that contains silver as the main component and at least one of palladium and platinum, the, external electrodes being made of a conductive material including silver as a main component and glass,

• wherein the proportion of silver contained in electrically conductive material of the internal electrode near the junction with the external electrode is higher than the proportion of silver contained in electrically conductive material of the internal electrode located inside of the stack.