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 drive control device 100, which controls driving of a vibration type actuator 200 including a vibrator 214 that includes a piezoelectric element 203, and a rotor 207, includes amplifier circuits 11 and 12 amplifying a power supply voltage to generate a drive voltage to be applied to the piezoelectric element 203, and a microcomputer unit 1. The microcomputer unit 1 performs a control to increase the amplitude of the drive voltage to perform acceleration from when the vibration type actuator 200 is started to when a target speed of the rotor 207 is reached, decrease the frequency of the drive voltage without changing the amplitude of the drive voltage when power supplied to the piezoelectric element 203 exceeds a first power limit P-Lim.sub.1, and increase the amplitude of the drive voltage when the power falls below a second power limit P-Lim.sub.2 during an operation of decreasing the frequency.

A vibration actuator includes a vibrator including a shaft, an output transmission member penetrated by the shaft, and configured to rotate about the axis of the shall, and a fixed member configured not to move relative to the shaft and configured to move relative to the output transmission member. The fixed member includes a base portion and a projection portion protruding from the base portion to the output transmission member side, the vibration actuator includes a pressure reception member between the base portion and the output transmission member in an axial direction of the shaft, and wherein the projection portion and the output transmission member are in contact with each other in a direction orthogonal to the axial direction of the shaft, and the projection portion and the output transmission member are not in contact with each other in the axial direction of the shaft.

A control apparatus for a vibration-type actuator which improves acceleration performance and deceleration performance in driving the vibration-type actuator. The vibration-type actuator moves a vibrating body and a driven body relatively to each other. A vibration state of the vibrating body is detected based on a vibrating voltage or driving current generated in response to vibrations of the vibrating body. A relative speed of the vibrating body and the driven body is detected, and based on the detected vibration state and the detected relative speed, the vibration state of the vibrating body is controlled.

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 piezoelectric material includes: an oxide containing Na, Ba, Nb, Ti, and Mn, in which the oxide has a perovskite-type structure, a total amount of metal elements other than Na, Ba, Nb, Ti, and Mn contained in the piezoelectric material is 0.5 mol % or less with respect to a total amount of Na, Ba, Nb, Ti, and Mn, a molar ratio x of Ti to a total molar amount of Nb and Ti is 0.05x0.12, a molar ratio y of Na to Nb is 0.93y0.98, a molar ratio z of Ba to Ti is 1.09z1.60, a molar ratio m of Mn to the total molar amount of Nb and Ti is 0.0006m0.0030, and 1.07yz1.50 is satisfied.

Provided is a lead-free piezoelectric material reduced in dielectric loss tangent, and achieving both a large piezoelectric constant and a large mechanical quality factor. A piezoelectric material according to at least one embodiment of the present disclosure is a piezoelectric material including a main component formed of a perovskite-type metal oxide represented by the general formula (1): Na.sub.x+s(1y)(Bi.sub.wBa.sub.1sw).sub.1yNb.sub.yTi.sub.1yO.sub.3 (where 0.84x0.92, 0.84y0.92, 0.002(w+s)(1y)0.035, and 0.9w/s1.1), and a Mn component, wherein the content of the Mn is 0.01 mol % or more and 1.00 mol % or less with respect to the perovskite-type metal oxide.

A lead-free piezoelectric material includes perovskite-type metal oxide containing Na, Nb, Ba, Ti, and Mg and indicates excellent piezoelectric properties. The piezoelectric material satisfies the following relational expression (1): 0.430a0.460, 0.433b0.479, 0.040c0.070, 0.0125d0.0650, 0.0015e0.0092, 0.93ecd1.13e, a+b+c+d+e=1, where a, b, c, d, and e denote the relative numbers of Na, Nb, Ba, Ti, and Mg atoms, respectively.

A controller is capable of improving position detection accuracy during the stopping of an actuator, and controlling the actuator with high stability and quick responsiveness during driving. A first position signal corresponding to an amount of relative movement between the actuator and a driven element is output to a filter, and the filter outputs a second position signal generated by attenuating signal components having frequencies except a specific frequency band. Driving and stopping of the actuator are controlled according to the second position signal. As the specific frequency band, a first frequency band is set in the filter during the driving of the actuator, and a second frequency band is set in the filter during the stopping of the actuator. The first frequency band and the second frequency band both include 0 Hz, and the second frequency band is narrower than the first frequency band.

A vibration-type actuator capable of suppressing reduction in holding torque or holding force under influence of humidity. A vibration-type actuator 10 includes a vibrating body 2 and a driven body 1. The vibrating body 2 has a piezoelectric element 2c and an elastic body 2b. The driven body 1 is in contact with the vibrating body 2. The vibration-type actuator 10 moves the vibrating body 2 and the driven body 1 relatively to each other by vibration excited to the vibrating body 2. At least one of a first contact portion of the vibrating body 2 and a second contact portion of the driven body 1 includes a stainless-steel sintered body with pores and at least some of the pores are impregnated with a resin.