JP3067294B2 - Ferroelectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving a ferroelectric ceramic composition represented by piezoelectric ceramics.

[0002]

2. Description of the Related Art A ferroelectric porcelain composition (hereinafter referred to as "ferroelectric material") is applied to a driving portion (actuator) of a fine positioning device or the like by utilizing the property (reverse voltage effect) that a ferroelectric material is deformed by strain when a strong voltage is applied. Abbreviated as “dielectric”).

[0003]

The above ferroelectric material is applied to a phase boundary which is generally considered to have the best characteristics when a voltage of about 1 V (volt) is applied. .

However, a ferroelectric selected based on characteristics near a phase boundary is easily affected by the ambient temperature, and it is necessary to perform appropriate temperature correction.

Further, as the actuator, the larger the strain displacement, the better, and it is desirable to increase the applied voltage to, for example, 1 KV. However, the conventional actuator is too short to apply such a high voltage and is not practical.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ferroelectric material having electric field characteristics capable of withstanding a high voltage, durability and good temperature characteristics.

[0007]

In order to achieve the above object, the present invention provides a ferroelectric porcelain composition comprising Pb (Mg1 / 3
_{Nb2 / 3) O 3 -PbZrO 3} -PbTiO 3 system to Bi
Addition of additives such as ₂ O ₃ , SnO ₂ , ZnO, SrO or Pb (Mg1 / 3Nb2 / 3) O ₃ -PbZrO _3-
A PbTiO ₃ system, wherein the crystal system is a tetragonal system, and the Zr ratio represented by Zr / (Zr + Ti) is set to be at least 0.5 mol% smaller than the Zr ratio at the phase boundary.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor has proposed a conventional Pb (Mg1 / 3Nb2 / 3).
O ₃ -PbZrO ₃ -PbTiO ₃ system ferroelectric intensive research as a result in order to improve the disadvantages of, Pb (Mg1 / 3Nb2 / 3 ) O
_A trace amount of Bi ₂ is added to the ₃ -PbZrO ₃ -PbTiO ₃ ferroelectric.
O _3, SnO _2, ZnO, those that have been added SrO or _{Pb (Mg1 / 3Nb2 / 3)} O 3 -PbZrO 3 -PbTiO
_{The three-} system and tetragonal ferroelectrics have excellent electric field characteristics and durability, and have a very unique ferroelectric porcelain composition which is hardly affected by environmental temperature changes. The present invention has been found to be obtained, and the details thereof are as described below.

FIG. 1 is a graph showing the relationship between the Zr ratio and the strain of a ferroelectric material including a ferroelectric material according to the present invention.
The figure shows the result of applying a voltage of 0 V and measuring the strain using a non-contact laser displacement meter and a strain gauge.

The above Zr ratio is Zr / (Zr + Ti)
And means the molar fraction of Zr contained in the composition. For notation, this is multiplied by 100 and expressed in mole percent.

According to FIG. 1, the strain becomes maximum when the Zr ratio is around 40.0. This is considered to be a composition in which the composition near the phase boundary is soft and easily deformed. Conventionally, the composition in the vicinity of the phase boundary has been adopted because the strain is large.

FIGS. 2 to 4 are diagrams showing the change in d constant when a voltage is applied to a ferroelectric material including the ferroelectric material according to the present invention. m
m, and a piezoelectric d constant (hereinafter, referred to as “d constant”) calculated based on the 31-direction distortion generated at this time.
Abbreviated. ) Is plotted.

FIG . 2 shows the results for a sample having a Zr ratio of 35.5 to 39.0, that is, a tetragonal system. As the Zr ratio increases, the d constant increases. The d constant is almost directly proportional to the magnitude of. But Z
When the r ratio is 39.0, it tends to decrease around 1000 V / mm as a peak.

FIG . 3 shows a sample having a Zr ratio of 40.0, that is, a sample near the phase boundary.
It tends to decrease from around V / mm.

FIG . 4 is for a sample having a Zr ratio of 41.5 or 43.0, that is, a rhombohedral or pseudo-cubic system, and cannot be said to have a small d constant and a proportional relationship with an increase in the electric field. .

As can be seen from FIGS. 2 to 4 , in order to obtain a relatively large d constant and a d constant proportional to the strength of the electric field, it is necessary to use a tetragonal system and a Zr ratio of about 38.5. Can be said to be preferable.

FIG . 5 is a graph showing the temperature effect of the ferroelectric substance including the ferroelectric substance according to the present invention. The vertical axis represents the distortion factor at 60 ° C. when 0 ° C. is set to 1.0. In the case of the crystal system, the strain rate is about 1.1, while the strain increases sharply near the phase boundary, and in the rhombohedral system or the pseudo-cubic system, it rapidly increases 1.2 to 1.9 times or more. This shows that the tetragonal sample is least affected by changes in the ambient temperature.

FIG . 6 is a graph showing the rate of change in strain of a ferroelectric including the ferroelectric according to the present invention in a voltage repetition durability test.
It shows the rate of change of strain after the application of 00 times, 10,000 times and 100,000 times.
Deterioration is also observed in rhombohedral or pseudo-cubic systems.

On the other hand, in the tetragonal system, the degree of deterioration is small even after 100,000 times, and the durability is large.

From the above, it is preferable that the ferroelectric ceramic composition suitable for the actuator is a tetragonal system and has a Zr ratio smaller than the Zr ratio at the phase boundary by at least 0.5 mol%.

If the setting of the Zr ratio is too close to the phase boundary, each characteristic tends to be unstable. If the setting of the Zr ratio is too small, the generated distortion becomes small as shown in FIG. Therefore, in the embodiment shown in FIGS.
Preferably, the ratio is set in the range of 38.0-38.5.

Note that Pb (Mg1 / 3Nb2 / 3) O ₃ -Pb
Additives for ZrO ₃ -PbTiO ₃ system Bi ₂ O _3, Sn
Not limited to O ₂ , ZnO, SrO, BaO, CaO, MnO ₂
And the like. Further, the ferroelectric of the present invention is not limited to piezoelectric ceramics, and can be used as a ferroelectric in a broad sense.

[0023]

As described above, the ferroelectric porcelain composition of the present invention is tetragonal, and maintains a good proportional relationship with a strong electric field, generates a large strain, and is hardly affected by a change in the temperature of the atmosphere. And good durability. Therefore, according to the present invention, a high-output and highly reliable ferroelectric ceramic composition can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a Zr ratio and a strain of a ferroelectric including a ferroelectric according to the present invention.

FIG. 2 is a diagram showing a change in d constant when a voltage is applied to a ferroelectric including a ferroelectric according to the present invention.

FIG. 3 is a diagram showing a change in d constant when a voltage is applied to a ferroelectric including a ferroelectric according to the present invention.

FIG. 4 is a diagram showing a change in d constant when a voltage is applied to a ferroelectric including a ferroelectric according to the present invention.

FIG. 5 is a diagram showing the temperature influence of a ferroelectric including a ferroelectric according to the present invention.

FIG. 6 is a diagram showing a rate of change in strain of a ferroelectric including a ferroelectric according to the present invention by a voltage repetition durability test;

Continuation of the front page (56) References JP-A-1-305856 (JP, A) JP-B-45-30151 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 41 / 187 C04B 35/49

Claims (1)

(57) [Claims] 1. Pb (Mg1 / 3Nb2 / 3) O ₃ -PbZr
O ₃ -PbTiO ₃ system _{Bi 2 O 3, SnO 2,} ZnO, S
Rb or other additives or Pb (Mg1 / 3N
b2 / 3) O ₃ —PbZrO ₃ —PbTiO ₃ system whose crystal system is tetragonal and the Zr ratio represented by Zr / (Zr + Ti) is at least 0.5
A ferroelectric porcelain composition characterized in that it is set to be smaller by mole percent.