JPH0342706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an element that digitally controls minute displacements.

(Prior art) Conventionally, as an element for digitally controlling micro-displacement, an element has been proposed in which ferroelectric piezoelectric ceramics having different plate thicknesses are laminated and each piezoelectric plate is driven individually and independently. (Unexamined Japanese Patent Publication No. 1973-
35994). Here, the thickness of each piezoelectric plate is 2 ⁿ (n: integer)
Displacement can be digitally controlled by setting them to be a proportional series of , applying a voltage that saturates the generated distortion to each, and driving them independently.

(Problems to be Solved by the Invention) However, the magnitude of strain generated in ferroelectric piezoelectric materials generally increases as the electric field strength increases. Even if the electric field is saturated at a certain electric field strength, this electric field strength will be a very large value, so the drive voltage will inevitably become high. Furthermore, under such high voltages, the dielectric strength of the material becomes a problem, resulting in low reliability and not being a practical device.

An object of the present invention is to provide a digital micro-displacement element which solves this problem and can be driven at a low voltage.

(Means for Solving the Problems) The gist of the present invention is to construct a laminate using a material that undergoes a phase transition from a ferroelectric phase to a ferroelectric phase when an electric field is applied, and that simultaneously undergoes volume expansion. The structure is such that each layer can be driven independently.

Here, the thickness of each layer of the laminate may be equal or may have a ratio series relationship of ²ⁿ .

(Function) For example, if the composition is Pb _0.99 Nb _0.02 [(Zr _0.6 Sn _0.4 ) _0.94
The antiferroelectric material represented by Ti _{0.06 ] 0.98} O ₃ has a voltage of about 3KV/
When an electric field of mm or more is applied, it undergoes a phase transition to a ferroelectric substance,
At the same time, it is known that the dimensions increase by about 0.15% in the direction of the electric field. The amount of elongation is not in a comparative relationship with the electric field intensity like piezoelectric strain, but is generated due to phase transition, so the amount of elongation is constant and does not change even if the electric field intensity increases. Furthermore, this material has the characteristic that when the electric field is removed, a phase transition occurs again to the antiferroelectric phase, and the dimensions return to their original values.

Therefore, by constructing a multilayer body using such materials,
By driving each layer independently, a minute displacement control element whose displacement amount changes digitally can be obtained.

(Examples) The present invention will be described in detail below based on Examples.

FIG. 1 shows an embodiment of the present invention, in which antiferroelectric ceramics Pb _0.99 Nb _0.02 [(Zr _0.6 Sn _0.4 ) _0.94 with equal thicknesses are provided with metal electrode films 13 on both main surfaces.
Ti _0.06 ] _0.98 O ₃ plates 11 are laminated in the thickness direction with an insulator 12 in between. The lower electrodes of each antiferroelectric ceramic plate are electrically connected and taken out as a common terminal 14. In addition, 15, 16, 17, 18, 19, 2
Electrode terminals 0 and 21 are taken out.

Furthermore, FIG. 2 shows the relationship between the amount of displacement of the element in the height direction and the number of driven layers. Now, if an electric field greater than the critical electric field that causes a phase transition in the ferroelectric is applied to any one layer, that layer will undergo a certain displacement in the thickness direction. If two layers are driven simultaneously, the amount of displacement generated will be doubled. In this way, by changing the number of layers to be driven, the amount of displacement generated also changes digitally.

It goes without saying that the step of displacement can be changed by changing the thickness of each antiferroelectric material.

(Effects of the Invention) As described above, it can be seen that minute displacements can be digitally controlled by using the element of the present invention.

In this case, since the generated strain does not depend on the electric field intensity unlike in conventional elements using ferroelectric materials, there is an advantage that highly accurate displacement control can be performed even with rough voltage control.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example in which displacement is controlled using this element. In the figure, 11 is an antiferroelectric ceramic plate, 12 is an insulating plate, 13 is a metal electrode layer, 14 is a common electrode terminal,
15 to 21 indicate independent electrode terminals.

Claims (1)

[Claims] 1 It has a structure in which layers of an antiferroelectric material that undergoes a phase transition to a ferroelectric phase when an electric field is applied and layers of an insulating material are laminated alternately via electrode layers, and each electrode layer is alternately stacked with a common electrode. A ceramic displacement element characterized in that the other electrode layers are connected to independent electrodes.