BaTiO3-PbTiO3 series single crystal and method of manufacturing the same, piezoelectric type actuator and liquid discharge head using such piezoelectric type actuator

Abstract

BaTiO3-PbTiO3 series single crystal is single-crystallized by heating BaTiO3-PbTiO3 compact powder member or sintered member having a smaller Pb-containing mol number than Ba-containing mol number, while keeping the powder or substance in non-molten condition. In this way, this single crystal can be manufactured at a crystal growing speed faster still and stabilized more, significantly contributing to improving the dielectric loss and electromechanical coupling coefficient for the provision of excellent BaTiO3-PbTiO3 series single crystal in various properties, as well as for the provision of piezoelectric material having a small ratio of lead content, which is particularly excellent in piezoelectric property and productivity.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to the BaTiO.sub.3--PbTiO.sub.3 series single crystal that can be utilized as a piezoelectric element, for example, and also, relates to the method of manufacturing the same. Further, the invention relates to a piezoelectric type actuator formed by the BaTiO.sub.3--PbTiO.sub.3 series single crystal, and the liquid discharge head that uses such piezoelectric type actuator as well.[0003] 2. Related Background Art[0004] The BaTiO.sub.3 series single crystal is a nonlinear optical crystal utilized for optical communications, information processing, or the like, and having a great marketability, which is not only used as a phase conjugate wave generating medium for a high resolution image processing, a real-time hologram, or a laser resonator, but also, used as a highly capable piezoelectric material if the crystallization thereof can be implemented at lower costs.[0005] Now, obviously, the composition of the BaTiO.sub....

AI Technical Summary

Benefits of technology

[0013] From the viewpoint of the BaTiO.sub.3--PbTiO.sub.3 series single crystal as a piezoelectric material, it has such advantages as the wide range of temperatures at which it can be used, and the lower amount of lead content that it has attained, as well as the excellent piezoelectric property that it can provide. The curie temperature of BaTiO.sub.3 series single crystal is approximately 120.degree. C. (T.sub.c). Any element that uses the BaTiO.sub.3 series single crystal has a narrow usable temperature range due to low T.sub.c as practical drawbacks. The BaTiO.sub.3--PbTiO.sub.3 series single crystal of the present invention has a higher curie temperature (T.sub.c) than the aforesaid BaTiO.sub.3 polycrystal to make it possible to make the range of usable temperature larger.

Problems solved by technology

Now, obviously, the composition of the BaTiO.sub.3 makes it difficult to obtain single crystal directly from the BaTiO.sub.3 solution when BaTiO.sub.3 series single crystal is manufactured.

Also, for the TSSG method, not only an expensive noble metal crucible, such as a platinum crucible, is needed, but the growing speed is slow to make the manufacturing costs extremely high.

With these methods, however, the mono-crystalline growth rate greatly varies to make it impossible to grow any bulky single crystal with good reproducibility.

Also, the rearrangement density is high, and the crystallinity of the BaTiO.sub.3 series single crystal thus obtained is inferior to the one obtained by the conventional TSSG method and the flux method.

This method makes the manufacturing apparatus and process complicated, because there is a need for a process to melt the crystal oxide.

Also, the single crystal thus obtained has inferior crystallization properties, and only the crystal that has a high ratio of pore content is obtainable eventually.

However, this method is not fully satisfactory in terms of the time required for manufacturing and costs.

This material aims at obtaining a high photo-refractivity in the near infrared range, but Mg, Fe, or some other element, which may exert unfavorable influence on the piezoelectric property, is contained in that material.

As a result, it is not preferable to use this as a piezoelectric material.

Also, for the utilization at the industrial level, it is not satisfactory in terms of the time required for manufacture and costs.

As described above, the TSSG or flux method for manufacturing BaTiO.sub.3 series single crystal makes it extremely difficult to improve problems related to manufacturing efficiency, such as the time required for manufacturing and costs, among some others.

Here, although the sintering method is anticipated to enhance the manufacturing efficiency, the variation of growing speed of BaTiO.sub.3 series single crystal makes it impossible to obtain any satisfactory result, and also, the crystallinity of the BaTiO.sub.3 series single crystal thus obtained is inferior to the one obtainable by means of TSSG or flux method.

In other words, it has been difficult to implement the manufacture of BaTiO.sub.3 series single crystal having excellent crystallinity and property in a shorter period of time at lower costs.

Any element that uses the BaTiO.sub.3 series single crystal has a narrow usable temperature range due to low T.sub.c as practical drawbacks.

Therefore, the piezoelectric property is not satisfactory.

Also, the piezoelectric property of the BaTiO.sub.3--PbTiO.sub.3 polycrystal is far inferior in terms of a piezoelectric material to that of the PZT polycrystal or the BaTiO.sub.3--PbTiO.sub.3 series single crystal, and there is no way fundamentally to enhance the piezoelectric property as single crystal.

Also, for the TSSG method, an expensive noble crucible, such a platinum crucible, is needed.

In addition, the growing speed is only 0.1 to 0.2 mm / h approximately, leading to an extremely high cost of manufacture.

Further, the material loss is great, and there is a drawback that it is difficult to obtain bulky crystal.

Such an extremely high cost of manufacture is inevitable to make the field of utilization thereof extremely limited.

It has been pointed out that this is valueless as a material of industrial use.

There are often the cases where the anticipated performance cannot be demonstrated after all.

It is also anticipated that there is the same problem regarding the BaTiO.sub.3--PbTiO.sub.3 series single crystal if it should be manufactured using the melt-solidification method.

In order to suppress the Pb evaporation, it is imperative that a pressurized container be utilized, presenting a disadvantage that the manufacturing costs become higher.

In order to suppress the Pb evaporation, it is imperative that a pressurized container be utilized, presenting a disadvantage that the manufacturing costs become higher.

In order to suppress the lead evaporation, it is imperative that a pressurized container be used, which leads to such an unfavorable problem of increased cost of manufacture.

In order to suppress the lead evaporation, there are often the cases where only the execution of the heating process under the lead atmosphere as described earlier is not good enough.

As compared with the precess under the normal pressure, this is unfavorable in terms of the productivity and costs.

In this respect, if the ratio of pore content of the sintered member exceed 5 volume %, the ratio of pore content in the single crystal obtained by the crystal growth is also increased, which unfavorably lowers the mechanical strength thereof.

However, there is no practical problem since most of the components move to a distal end of the grown crystal.

Also, if the value is approximately less than 0.1 volume %, this method is not good enough in terms of precision.

The sintered member thus obtained is composed of minute crystal grain of average granular diameter of approximately 3 .mu.m, thus making it impossible to obtain the single crystal in a size sufficient enough to be used as seed crystal.

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