JPS6021937B2 - Piezoelectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric ceramic composition used, for example, in a vibrator for an ultrasonic probe of an ultrasonic deep wound machine.

Conventionally, compositions corresponding to this type include (Na, Li
) Although Nb03 is used, it has poor binding properties, and normal binding without hot pressing does not increase the density sufficiently, making it impossible to obtain good piezoelectric properties and sufficient mechanical strength.

The present invention solves the drawbacks of the following (Na, Li
) By adding aluminum oxide (AI203) to Nb03 as a subcomponent, a ceramic composition with high density, a large frequency constant, and good shoelectric properties is provided. In other words, the present invention uses aluminum oxide (mount 203
) from 0.03 to 2. % by weight was added. As a result, the molded product has characteristics such as a small dielectric constant, a large electromechanical coupling coefficient in the thickness direction, and is dense and has high mechanical strength. It not only facilitates the firing of the material, but also enables production with stable quality even on a mass production scale.
Furthermore, the piezoelectric magnetic composition of the present invention has a large frequency constant and, as mentioned above, a small dielectric constant, so it is particularly useful as a piezoelectric material for high frequencies.

Further, the piezoelectric magnetic composition of the present invention has a small electromechanical coupling coefficient in the vertical direction, so that the secondary vibration is small, and when only thickness direction vibration is used, it is particularly useful as a vibrator. The present invention will be explained below using an example.

First, each powder of niobium pentoxide, sodium carbonate, and lithium carbonate with a purity of 99.5% or higher was weighed out in a predetermined proportion, and alcohol was added to the powder for 1 hour using a ball mill using a nylon pot and zirconia balls. Mix. Next, it is taken out, dried, and then pressed at a pressure of about 500k9/block. It is placed in a high-purity alumina porcelain with a lid and calcined for 3 hours at 900 qo ~ 00 pi 0. Next, after coarsely pulverizing with a Lykai machine, pulverizing is performed for 2 beats with a ball mill in the same manner as during mixing. 99.9% purity in dry powder
Above, a predetermined weight of aluminum oxide with an average grain size of 1r or less was added, and after mixing for 1 hour in a Lykai machine, 2.5% PVA was added.
A 10% solution was added and granulated through a mesh. The pelleted powder was press-molded to a diameter of 24 ribs and a thickness of 3.5 ribs at a pressure of 700 kg/unit. 11 with the same composition as the molded product.
Temporarily hold at 50℃, sprinkle with coarsely ground powder using a Lykai machine, place it in a high-purity alumina porcelain with a lid, and heat to 1180 qo.
It was baked at ~1240 qo for 3 hours. Both sides of the competitive product were polished to a thickness of 2.5 and used as a sample for density measurement. Further, the thickness was increased to 0.6 mm, and silver electrodes were attached to both sides to prepare a sample for measuring electrical characteristics. The polarization treatment was performed in silicone oil at 100° C. for 50 minutes using a DC voltage of V/skin.

The results of measuring various properties of the samples produced by the above method are shown in the table. The components of the samples in the table include the main component sodium niobate (NaNb03) and lithium niobate (Li
The ratio of Nb03) was changed, and the subcomponent aluminum oxide (AI203) was varied in five stages (0.0.
03, 0.50, 1.0, 2. % by weight).

In the table, for example, Sample M does not contain AI203, Samples ■~[Skinma AI202 is added from 0.02 to 2.
A comparison of the properties shows that the density is higher, the frequency constant is larger, and the mechanical quality factor is higher when AI203 is added.

Similar results can be seen for other samples below. The reason why the amount of AI203 added is limited to 0.02 to 2.00% by weight is because, for example, if it is less than 0.02% by weight, the sinterability will be poor and the density will be low, which is the same as when no mountain 203 is added. This is because it becomes impractical. Also, 2.
This is because adding more than 0% by weight deteriorates the coupling coefficient in the thickness direction and lowers the density. As is clear from the table above, according to the composition of the present invention, by adding the subcomponent aluminum oxide (mountain 203), a porcelain composition with high density, large frequency constant, and good piezoelectric properties can be easily produced. can get.

Claims (1)

[Scope of Claims] 1 The basic composition is a solid solution represented by the following general formula Na_1-xLixNbO_3 where 0.02≦X≦0.30, and aluminum oxide (Al_2O_3) is added as a subcomponent by 0.0% to the total amount. A piezoelectric magnetic composition characterized in that it contains 0.03 to 2.0% by weight.