There is provided a lead-free piezoelectric material having a satisfactory piezoelectric constant and mechanical quality factor in the range of device operating temperatures (from 30 C. to 50 C.). The piezoelectric material contains a main constituent containing a perovskite-type metal oxide expressed by the general formula (Ba.sub.1-xCa.sub.x).sub.a(Ti.sub.1-yZr.sub.y)O.sub.3, where x, y and a satisfy the 0.030x<0.090, 0.030y0.080, and 0.9860a1.0200. The material also contains 0.040 to 0.500 part by weight of Mn, 0.042 to 0.850 part by weight of Bi, 0 to 0.028 part by weight of Li, 0.001 to 4.000 part by weight of a third sub-constituent including at least one of Si and B, and 0.001 to 4.000 parts by weight of Cu, each in terms of element relative to 100 parts by weight of the metal oxide.

A piezoelectric material which is low in load on the environment, and also satisfies both the requirements of a high piezoelectric constant and a high mechanical quality factor. The piezoelectric material comprises a plurality of crystal grains containing Ba, Ca, Ti, Zr, Mn, and O. An average equivalent circle diameter of the crystal grains is not smaller than 1.0 m and not larger than 10 m. The crystal grains include crystal grains A each having a first domain with a width of not smaller than 300 nm and not larger than 800 nm, and crystal grains B each having a second domain with a width of not smaller than 20 nm and not larger than 50 nm.

A piezoelectric element includes a piezoelectric material layer and an electrode layer, wherein the piezoelectric material layer and the electrode layer are stacked on top of each other, the piezoelectric material layer includes a barium titanate-based material, and two coercive fields Ec1 and Ec2 of the piezoelectric element have the same sign and satisfy (|Ec2||Ec1|)8 kV/cm.

A piezoelectric element, in which a piezoelectric material layer has a plurality of crystal particles and a plurality of void portions and, in at least one of two or more of the piezoelectric material layers, when the average thickness in the lamination direction of the piezoelectric material layer is defined as T.sub.P, the average circle-equivalent diameter of the plurality of crystal particles is defined as D.sub.G, the maximum length in the lamination direction of the plurality of void portions not contacting the electrode layers is defined as L.sub.V, and the average thickness of the electrode layers contacting the at least one piezoelectric material layer is defined as T.sub.E, 0.07T.sub.PD.sub.G0.33T.sub.P and T.sub.EL.sub.V0.3T.sub.P are established and the lead content is less than 1000 ppm.

A control apparatus controls driving a vibratory actuator. The control apparatus applies a signal to an electromechanical energy conversion device of a vibrator of the vibratory actuator to excite vibration on the vibrator and cause the vibrator and a driven object contacting the vibrator to move relative to one another by the vibration. If the vibratory actuator decelerates, the control apparatus changes a driving frequency of the signal to a frequency higher than a start-up frequency of the vibratory actuator and a preceding frequency at a deceleration start position. After changing the driving frequency of the signal, the control apparatus controls the signal driving frequency to perform deceleration control and fixes voltage of the signal in a deceleration period in which the vibratory actuator is decelerated.

A vibration actuator includes an electro-mechanical transducer, a vibrating body fixed to the electro-mechanical transducer, the vibrating body being vibrated by applying a voltage to the electro-mechanical transducer, and a driven body contacting the vibrating body. The driven body is frictionally driven by a vibration of the vibrating body. The driven body includes a first extended portion extending from a main body portion of the driven body towards an inside diameter side of the vibrating body, a second extended portion extending from the first extended portion towards the outside diameter side of the vibrating body, and a contact surface provided at a tip of the second extended portion. The contact surface contacts the vibrating body. The first extended portion, the second extended portion, and the contact surface are each capable of elastically deforming in a rotational axis direction of the driven body.

The piezoelectric material of the present invention includes a main component composed of a perovskite-type metal oxide represented by Formula (1), at least one of Mn and Ni, and Mg. The content of Ni is 0 mol or more and 0.05 mol or less based on 1 mol of the perovskite-type metal oxide, and the content of Mn is 0 mol or more and 0.005 mol or less based on 1 mol of the perovskite-type metal oxide, provided that the content of Mn and the content of Ni are not simultaneously 0 mol. The content of Mg is 0.001 mol or more and 0.020 mol or less based on 1 mol of the perovskite-type metal oxide. Formula (1): (Na.sub.xBa.sub.1-y)(Nb.sub.yTi.sub.1-y)O.sub.3 (where x is 0.83 or more and 0.95 or less, y is 0.85 or more and 0.95 or less, and x/y is 0.95 or more and 1.05 or less).

The piezoelectric material of the present invention includes a main component composed of a perovskite-type metal oxide represented by Formula (1), Zn, and Mg. The content of Zn is 0.005 mol or more and 0.050 mol or less based on 1 mol of the perovskite-type metal oxide, and the content of Mg is 0.001 mol or more and 0.020 mol or less based on 1 mol of the perovskite-type metal oxide. Formula (1): (Na.sub.xBa.sub.1-y)(Nb.sub.yTi.sub.1-y)O.sub.3 (where x is 0.83 or more and 0.95 or less, y is 0.85 or more and 0.95 or less, and x/y is 0.95 or more and 1.05 or less).

There is provided a lead- and potassium-free piezoelectric material having a high piezoelectric constant and a satisfactory insulation property and a piezoelectric element that includes the piezoelectric material. The piezoelectric material contains a perovskite-type metal oxide having the general formula (1): (Na.sub.xBa.sub.1-y)(Nb.sub.yTi.sub.1-y)O.sub.3 (wherein x satisfies 0.80?x?0.95, and y satisfies 0.85?y?0.95); and at least one rare-earth element selected from La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, wherein the rare-earth element content is more than 0 mol % and 5 mol % or less of the amount of perovskite-type metal oxide. The piezoelectric element includes the piezoelectric material.

The present invention provides a piezoelectric material not containing lead and potassium, showing satisfactory insulation and piezoelectricity, and having a high Curie temperature. The invention relates to a piezoelectric material includes a main component containing a perovskite-type metal oxide represented by Formula (1): (Na.sub.xBa.sub.1-y)(Nb.sub.yTi.sub.1-y)O.sub.3 (wherein, 0.80?x?0.94 and 0.83?y?0.94), and an additive component containing at least one element selected from Mn and Ni, wherein the content of the Ni is 0 mol or more and 0.05 mol or less based on 1 mol of the perovskite-type metal oxide, and the content of the Mn is 0 mol or more and 0.005 mol or less based on 1 mol of the perovskite-type metal oxide.