Field of the Invention
The present invention relates to a piezoelectric element using alkali niobate piezoelectric ceramic, as well as a method of manufacturing such piezoelectric element.
Description of the Related Art
Piezoelectric elements are electronic components that utilize the characteristics of piezoelectric ceramics to convert electrical energy to mechanical energy and vice versa. Structurally, a piezoelectric element is constituted by a piezoelectric ceramic and a pair of electrodes sandwiching it.
Piezoelectric elements can convert mechanical energy, such as vibration or pressure, to electrical energy, and discharge the electrical energy as voltage between a pair of electrodes. On the other hand, piezoelectric elements can convert voltage between a pair of electrodes to mechanical energy, such as vibration or pressure, to move other objects or operate on its own.
As piezoelectric elements can generate vibrations of wide-ranging frequencies, they can be used in speakers, for example. To be more specific, piezoelectric elements can generate vibrations in frequency bands of 0 to 100 Hz that occur in our general living environment, vibrations in frequency bands of up to 20 kHz that can be recognized by humans as sounds, and vibrations in frequency bands of several to several tens of GHz such as electromagnetic waves.
On the other hand, piezoelectric elements can generate voltages in wide-ranging frequencies from the aforementioned vibrations.
Also, piezoelectric elements of laminated type are known. A laminated piezoelectric element is constituted in such a way that a laminate of multiple piezoelectric ceramic layers is sandwiched by internal electrodes. Typically, laminated piezoelectric elements are manufactured by sintering the piezoelectric ceramic layers and internal electrodes simultaneously. Laminated piezoelectric elements can be used in actuators, for example, because a large displacement can be obtained in the laminated direction of the multiple piezoelectric ceramic layers.
PZT piezoelectric ceramics offering high piezoelectric property are widely used for piezoelectric elements and laminated piezoelectric elements. In light of the trend of reducing the spread of lead in recent years, however, there is a search for Pb-free or low-Pb piezoelectric ceramics to replace the PZT counterparts. Technologies relating to Pb-free or low-Pb piezoelectric ceramics are disclosed in Non-patent Literatures 1 and 2, for example.
Also, alkali niobate piezoelectric ceramics are drawing attention, in particular, as Pb-free piezoelectric ceramics offering high piezoelectric property to replace the PZT counterparts. Technologies relating to alkali niobate piezoelectric ceramics are disclosed in Patent Literatures 1 to 9, for example.