KR20080081857A - Method of manufacturing piezoelectric ceramic - Google Patents

Abstract

A method of manufacturing a piezoelectric device is provided to improve a piezoelectric distortion characteristic of the piezoelectric device by adding P2O5 into TiO2 and ZrO2. A piezoelectric device(1) includes a piezoelectric layer(2) and an electrode pair(3A,3B). The piezoelectric layer is sandwiched between the electrodes. When a voltage is applied between the electrodes, an electric field is generated in the piezoelectric layer and the piezoelectric layer is contracted or extended. The piezoelectric layer is made of a piezoelectric material of a PZT(PB Zinconate Titanate)-group piezoelectric ceramic. phosphor elements are added in the piezoelectric material. The phosphor element is added in a chemical with a metal included in the piezoelectric layer. The phosphor elements are uniformly distributed in the piezoelectric layer.

Description

Method of manufacturing piezoelectric electronics {Method of manufacturing piezoelectric ceramic}

The present invention relates to a method of manufacturing a piezoelectric device.

Conventionally, piezoelectric elements are used for various uses, such as a sounding body, a sensor, and an actuator, for example. And as a piezoelectric element, a single plate piezoelectric element and a laminated piezoelectric element are known. The single plate piezoelectric element has a structure including a piezoelectric layer made of a piezoelectric group between a pair of electrode layers. In addition, the stacked piezoelectric element has a body having a structure in which a piezoelectric layer and internal electrodes are alternately laminated. In the laminated piezoelectric element, it is common that the body is covered with a protective layer composed of a plurality of piezoelectric layers on both end faces thereof in the stacking direction thereof.

The material of the piezoelectric device used for such a piezoelectric element is disclosed by Unexamined-Japanese-Patent No. 5-24917, for example.

In recent years, further improvement of piezoelectric distortion characteristics has been desired in piezoelectric layers of piezoelectric elements as described above. And the inventors discovered the technique which can significantly improve the piezoelectric distortion characteristic after careful research.

That is, an object of the present invention is to provide a method for manufacturing a piezoelectric electronic device, in which piezoelectric distortion characteristics are improved.

The inventors have found that piezoelectric distortion characteristics when P is contained in a piezoelectric material used in a piezoelectric device, and P is mixed with TiO ₂ raw material and ZrO ₂ raw material in the piezoelectric material as P ₂ O ₅ by a predetermined range. This significant improvement was found and the present invention was completed.

That is, a method for manufacturing a piezoelectric ceramic according to the invention, TiO ₂ raw material, ZrO ₂ raw material and manufacturing method of the piezoelectric ceramic by firing a piezoelectric material containing by mainly composed of PbO raw material to produce a piezoelectric ceramic, TiO ₂ material, and It is characterized by mixing P ₂ O ₅ contained in the ZrO ₂ raw material into the piezoelectric material in a range of 40 ppm or more and 350 ppm or less.

According to the present invention, there is provided a method of manufacturing a piezoelectric electronic device, in which piezoelectric distortion characteristics are improved.

The manufacturing method of the piezoelectric device of the present invention significantly improves the piezoelectric distortion characteristics.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, the form considered best is demonstrated in detail. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description is duplicated.

First, the piezoelectric element manufactured by the manufacturing method which concerns on embodiment of this invention is demonstrated, referring FIG. 1 is a perspective view showing a piezoelectric element according to an embodiment of the present invention. The piezoelectric element 1 shown in FIG. 1 is a single plate piezoelectric element, and includes a piezoelectric layer 2 of a piezoelectric element and a pair of electrode layers 3A and 3B arranged to sandwich the piezoelectric layer 2. In the piezoelectric element 1, when a voltage is applied between the electrodes 3A and 3B, an electric field is generated in the piezoelectric layer 2 sandwiched therebetween, and the piezoelectric layer 2 is displaced (stretching operation).

The piezoelectric layer 2 is a layer mainly composed of a piezoelectric material of PZT-based piezoelectric ceramics. The piezoelectric material of the piezoelectric layer 2 contains phosphorus element. In the piezoelectric material, phosphorus element is contained in the form of a compound with an atom, an oxide, or another metal contained in the piezoelectric layer 2 or the like. It is preferable that the phosphorus element is uniformly dispersed in the piezoelectric layer 2.

The electrode layers 3A and 3B are conductive layers composed mainly of metal. As metal contained in electrode layer 3A, 3B, Ag, Au, Cu, Ni, Pd, these alloys (for example, Ag-Pd alloy), etc. are mentioned.

Next, the procedure for producing the piezoelectric element will be described with reference to FIG. 2. 2 is a flowchart illustrating a method of manufacturing a piezoelectric element according to an embodiment of the present invention.

When producing the piezoelectric element 1, first, starting materials are prepared (step 11). The starting material contains a PZT piezoelectric material as a main component. And weighing the respective raw materials the art as the piezoelectric _{material, PbO, TiO 2, ZrO 2} , it may be mentioned powdery raw material such as ZnO, Nb ₂ O _5, those of the powder raw material is a predetermined compositional ratio.

Next, by the ball mill which used the stabilized zirconia ball for the media, wet mixing of the said several types of starting raw material is performed about 24 hours (step S12). Then, the mixed raw material is dried (step S13). And the plasticity which heat-processes about 2 hours is performed about the mixed raw material at the temperature of about 850 degreeC, for example (step S14). Thereby, the raw material composition of the composite oxide piezoelectric material which has a perovskite structure mainly containing Pb, Zr, and Ti elements is obtained.

The raw material composition is wet-pulverized by a ball mill (step S15), and then dried (step S16) to obtain powder (piezoelectric powder) of the raw material composition. Subsequently, a binder such as a polyvinyl alcohol-based powder is added to the piezoelectric powder to granulate it (step Sl7), and this is molded into a rectangular plate shape by press molding or the like (step S18). Thereby, the piezoelectric green sheet which becomes a piezoelectric magnet is obtained.

The obtained piezoelectric green sheet is placed on a stabilized zirconia setter or the like, and then degreased to remove binders and the like contained in the piezoelectric green sheet by heating in an air atmosphere (step S19; debinder). And about the piezoelectric green sheet, the baking process (main baking) which heats about 1050-1200 degreeC for about 2 hours is performed in a sealed container (step S20).

Finally, silver paste is sintered on both surfaces of the obtained fired body to form electrode layers 3A and 3B (step S21). Thereby, the piezoelectric element 1 of FIG. 1 comprised from the piezoelectric layer 2 which is a baked piezoelectric group, and the electrode layers 3A, 3B sintered on both surfaces thereof is obtained.

As described above, in order to add P to the piezoelectric material, when it is mixed as P ₂ O ₅ from the TiO ₂ raw material and ZrO ₂ raw material in the piezoelectric material, as compared with the case where P is directly added to the piezoelectric material, The inventors have found that a piezoelectric group having excellent piezoelectric distortion property d31 is obtained.

However, TiO ₂ content of the elements of the raw material powder and ZrO ₂ powder in the raw material is a piezoelectric material, and in terms of P ₂ O ₅ is adjusted to a range of less than 40ppm 350ppm by mol based. That is, this amount of phosphorus element is mixed in the piezoelectric material. If the content of such phosphorus element is less than 40 ppm, the sintering of the piezoelectric material by firing may be insufficient, so that the density of the piezoelectric layer 2 may be lowered and sufficient displacement may be difficult to be obtained. On the other hand, when content of phosphorus element exceeds 350 ppm, the value of the piezoelectric distortion constant d31 will fall below a practical level.

In addition to the method described above, after applying the electrode paste (for example, a paste containing Ag-Pd alloy) to be the electrode layers 3A and 3B to the piezoelectric green sheet, the binder removal treatment (step S19) and the present method are performed. Even by firing (step S20), an element similar to the piezoelectric element 1 of FIG. 1 can be obtained. In this case, the metal contained in the electrode paste layer tends to diffuse in the piezoelectric green sheet at the time of main firing, but since the phosphorus element which is easily reacted with the metal is dispersed in the piezoelectric green sheet, the diffusion of the metal is caused by the piezoelectric green sheet. It is generated uniformly in the. As a result, shrinkage of the piezoelectric green sheet (piezoelectric layer 2) by sintering occurs uniformly as compared with the case where the piezoelectric green sheet does not contain phosphorus element. As a result, the piezoelectric layer 2 has a shape with little distortion, and the piezoelectric element 1 as a whole also has little distortion.

Example

Hereinafter, an Example demonstrates this invention further in detail.

Example

First, steps S11 to S16 shown in FIG. 2 were performed to obtain powder (starting raw material) of the raw material composition of the piezoelectric material. The starting materials include TiO ₂ and ZrO ₂ containing P ₂ O ₅ , and PbO, ZnO, and Nb ₂ O ₅ . And, these starting materials after firing were mixed in the open and weighed to obtain a piezoelectric ceramic having _{Pb 0 .99 [(Zn 1/} 3 Nb 2/3) 0.1 Ti 0 .44 _{0 .46} composition of Zr "O _3.

Next, as shown in step S17, a polyvinyl alcohol-based binder is added to the powder of the raw material composition of the piezoelectric material and granulated, and then press molding shown in step S18 is performed at about 196 MPa, and the one side is about one side. A plate-shaped piezoelectric green sheet having a size of 20 mm and a thickness of 1.5 mm was obtained.

Thereafter, as shown in step S19, the binder of the piezoelectric green sheet is removed, and as shown in step S20, the piezoelectric green sheet is placed in a sealed container of magnesia (MgO) and heated at 1150 ° C for 2 hours. This firing was performed. This obtained the piezoelectric group on each plate.

Finally, the obtained piezoelectric device was processed to a height of 1.0 mm, and silver sintered electrodes were formed on both surfaces thereof to produce a single plate piezoelectric element (12 mm x 3 mm) similar to the piezoelectric element shown in FIG. Further, the single plate piezoelectric element was subjected to polarization treatment (treatment condition: 3 kV / mm, 15 minutes) in a silicon oil at 120 ° C.

The piezoelectric distortion constant d31 of the single plate piezoelectric element obtained as described above was measured. As a measuring method, the piezoelectric distortion constant was computed from the capacitance, the resonance frequency, and the anti-resonance frequency of the element measured using the impedance analyzer. Moreover, the cross section of the piezoelectric machine was observed with the scanning electron microscope, and the average particle diameter of the piezoelectric particle was measured using image processing software (Mac View) as a circle equivalent diameter.

Comparative example

In the same manner as in the above-described example, steps S11 to S16 shown in FIG. 2 were performed to obtain powder of the raw material composition of the piezoelectric material. This starting material includes TiO ₂ , ZrO ₂ , PbO, ZnO, and Nb ₂ O _5, to which a P ₂ O ₅ reagent is added. And, such that the starting materials with a P ₂ O ₅ addition, the piezoelectric ceramic is obtained having _{Pb 0 .99 [(Zn 1/} 3 Nb 2/3) 0.1 Ti 0 .44 Zr 0 .46] the composition of the O ₃ after firing Weighed and blended.

Next, as shown in step S17, a polyvinyl alcohol-based binder is added to the powder of the raw material composition of the piezoelectric material and granulated, and press molding shown in step S18 is performed at about 196 MPa, and one side is about 20 mm, A plate-like piezoelectric green sheet having a size of 1.5 mm in thickness was obtained.

Thereafter, as shown in step S19, the binder of the piezoelectric green sheet is removed, and as shown in step S20, the piezoelectric green sheet is placed in a sealed container of magnesia (MgO) and heated at 1150 ° C for 2 hours. Firing was carried out. This obtained the piezoelectric group on each plate.

Finally, the obtained piezoelectric device was processed to a height of 1.0 mm, and further, silver sintered electrodes were formed on both surfaces thereof to produce a single plate piezoelectric element (12 mm x 3 mm) similar to the piezoelectric element shown in FIG. Further, the single plate piezoelectric element was subjected to polarization treatment (treatment condition: 3 kV / mm, 15 minutes) in a silicon oil at 120 ° C.

The piezoelectric distortion constant of the single plate piezoelectric element obtained as described above was measured in the same manner as in Example. Moreover, the cross section of the piezoelectric machine was observed with the scanning electron microscope, and the average particle diameter of the piezoelectric particle was measured using image processing software (Mac View) as a circle equivalent diameter.

The piezoelectric distortion constants measured by the said Example and the comparative example were as showing in the following Table 1 and the graph of FIG. Here, the horizontal axis of the graph of Figure 3, and shows a P ₂ O ₅ content (ppm) of a piezoelectric material, and the vertical axis represents the piezoelectric strain constant (pC / N).

Example P ₂ O ₅ content (ppm) 40 150 250 350 450 d31 characteristic (pC / N) 225 220 210 200 170 Comparative example P ₂ O ₅ content (ppm) - 150 250 350 450 d31 characteristic (pC / N) - 210 190 170 145

From these measurement results (Table 1 and the graph of FIG. 3), P ₂ O ₅ is mixed from the TiO ₂ powder raw material and the ZrO ₂ powder raw material in the piezoelectric material as compared with the comparative example in which P ₂ O ₅ was directly added to the piezoelectric material. It turned out that the value of the piezoelectric distortion constant becomes high in the Example made. In addition, when the content of phosphorus elements of the TiO ₂ powder raw material and the ZrO ₂ powder raw material in the piezoelectric material is 350 ppm or less on a mol basis in terms of P ₂ O ₅ , the piezoelectric distortion constant is a practically sufficient value (200 pC / N or more). ) On the other hand, P ₂ O ₅ Let exceeds 350ppm, discarded by the piezoelectric strain constant is smaller than the 200pC / N. Accordingly, the piezoelectric material P ₂ O ₅ from the incorporation of TiO ₂ and ZrO ₂ raw material is preferably not more than 350ppm.

In addition, the micrograph in an Example and a comparative example was as showing in FIG. From this photograph, as a result of measuring the average particle diameter of the piezoelectric particles, the graph shown in FIG. 5 was obtained. Here, the horizontal axis of the graph of Figure 5, and shows the piezoelectric material of P ₂ O ₅ content (ppm), and the vertical axis represents the average particle size (㎛) of the piezoelectric particles.

From these measurement results (photograph of FIG. 4 and graph of FIG. 5), when P ₂ O ₅ having the same concentration is contained in the piezoelectric material, compared with the case where P ₂ O ₅ was directly added to the piezoelectric material (Comparative Example), When P ₂ O ₅ is mixed in the piezoelectric material from the TiO ₂ powder raw material and the ZrO ₂ powder raw material (Example), it can be seen that the piezoelectric group is composed of piezoelectric particles having a large average particle diameter. That is, in the predetermined P ₂ O ₅ content range (40 ppm or more and 350 ppm or less), when comparing with arbitrary content, the average particle diameter according to an Example becomes larger than the average particle diameter according to a comparative example. Thus, since an average particle diameter becomes large in an Example compared with a comparative example, the piezoelectric element which concerns on an Example can implement | achieve higher sinterability.

This invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, although the single-plate piezoelectric element was demonstrated as an example as a piezoelectric element, it can be applied also to a laminated piezoelectric element suitably.

1 is a perspective view showing a piezoelectric element according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a method of manufacturing the piezoelectric element shown in FIG. 1.

3 is a graph showing a measurement result according to an embodiment of the present invention.

4 is a micrograph showing the measurement results according to the embodiment of the present invention.

5 is a graph showing a measurement result according to an embodiment of the present invention.

Claims (1)

A method for producing a piezoelectric device by firing a piezoelectric material containing a TiO ₂ raw material, a ZrO ₂ raw material, and a PbO raw material as a main component, wherein the P ₂ O ₅ contained in the TiO ₂ raw material and the ZrO ₂ raw material is not less than 40 ppm and 350 ppm. A method for producing a piezoelectric electron, which is incorporated into a piezoelectric material in the following range.

Images