A piezoelectric element is typically formed of a bulk-shaped or film-shaped piezoelectric material including a lower electrode and an upper electrode.
As a piezoelectric material, ABO3 type ceramics such as lead zirconate titanate (hereinafter, referred to as “PZT”) is generally used.
However, PZT contains lead at an A-site of a perovskite skeleton. Therefore, the environmental impact of the lead component is considered to be a problem. In order to address this problem, a piezoelectric material using a lead-free perovskite-type metal oxide has been proposed.
For example, as a piezoelectric material formed of a lead-free perovskite-type oxide, “Chemistry of Materials” 2006, Vol. 18, No. 21, pp. 4987-4989 describes Bi(Zn0.5Ti0.5)O3. However, although the Bi(Zn0.5Ti0.5)O3 is theoretically expected to have excellent piezoelectric performance, it is difficult to polarize the Bi(Zn0.5Ti0.5)O3 due to its high Curie temperature, and hence the piezoelectric performance thereof has not been clarified.
Further, a piezoelectric material containing BiFeO3 as a main component has been proposed. For example, Japanese Patent Application Laid-open No. 2007-287739 discloses a BiFeO3-based material containing La in an A-site. BiFeO3 is a satisfactory ferroelectric substance, and is reported to exhibit a high remanent polarization value at low temperatures. However, there remains a problem that sufficient piezoelectric strain cannot be obtained from BiFeO3.
Further, “Chemistry of Materials” 2007, Vol. 19, No. 26, pp. 6385-6390 discloses a BiAlO3 piezoelectric material obtained by a high-pressure synthesis method. However, the piezoelectric performance of BiAlO3 has also not reached a practically applicable range yet.
The present invention has been accomplished to cope with such problems, and an object of the present invention is to provide a piezoelectric material having good piezoelectricity, and a piezoelectric element, a liquid discharge head, and an ultrasonic motor each using the piezoelectric material.
A first piezoelectric material of the present invention that solves the above-mentioned problems includes a perovskite-type metal oxide represented by the following general formula (1):Ax(ZnjTi(1-j))l(MgkTi(1-k))mMnO3  General formula (1)where: A represents a Bi element, or one or more kinds of elements selected from the group consisting of trivalent metal elements and containing at least a Bi element; M represents at least one kind of an element selected from the group consisting of Fe, Al, Sc, Mn, Y, Ga, and Yb; and 0.9≦x≦1.25, 0.4≦j≦0.6, 0.4≦k≦0.6, 0.27≦l≦0.49, 0.19≦m≦0.46, 0.27≦n0.36, and l+m+n=1 are satisfied.
A second piezoelectric material of the present invention that solves the above-mentioned problems includes a perovskite-type metal oxide represented by the following general formula (1):Ax(ZnjTi(1-j))l(MgkTi(1-k))mMnO3  General formula (1)where: A represents a Bi element, or one or more kinds of elements selected from the group consisting of trivalent metal elements and containing at least a Bi element; M represents at least one kind of an element selected from the group consisting of Fe, Al, Sc, Mn, Y, Ga, and Yb; 0.9≦x≦1.25, 0.4≦j≦0.6, and 0.4≦k≦0.6 are satisfied; and l+m+n=1 is satisfied, and l, m, and n fall within a range surrounded by coordinate points A, B, C, D, E, F, G, H, I, and A, provided that the coordinate points A, B, C, and D, a line connecting the coordinate points A and B, a line connecting the coordinate points B and C, and a line connecting the coordinate points C and D are not contained in the above-mentioned range.A: (l, m, n)=(0.45, 0.19, 0.36)B: (l, m, n)=(0.27, 0.37, 0.36)C: (l, m, n)=(0.27, 0.46, 0.27)D: (l, m, n)=(0.49, 0.24, 0.27)E: (l, m, n)=(0.35, 0.52, 0.13)F: (l, m, n)=(0.23, 0.64, 0.13)G: (l, m, n)=(0.09, 0.64, 0.27)H: (l, m, n)=(0.09, 0.43, 0.48)I: (l, m, n)=(0.33, 0.19, 0.48)
A piezoelectric element of the present invention that solves the above-mentioned problems is a piezoelectric element including at least a piezoelectric material and a pair of electrodes provided in contact with the piezoelectric material in which the piezoelectric material is the above-mentioned piezoelectric material.
In a liquid discharge head of the present invention that solves the above-mentioned problems, the above-mentioned piezoelectric element is used. In an ultrasonic motor of the present invention that solves the above-mentioned problems, the above-mentioned piezoelectric element is used.
According to the present invention, there can be provided the piezoelectric material having good piezoelectricity, and the piezoelectric element, the liquid discharge head, and the ultrasonic motor each using the piezoelectric material.
Further, the piezoelectric material of the present invention does not affect an environment because the material does not use lead. In addition, the material is advantageous in terms of durability when used in a piezoelectric element because the material does not use any alkali metal.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.