JPH0742166B2 - Pyroelectric 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 pyroelectric porcelain composition and is used for infrared sensors such as human body sensors and gas sensors.

[0002]

2. Description of the Related Art Conventionally, lead titanate-based and lead zirconate titanate-based materials have been developed as pyroelectric porcelain compositions. Lead titanate-based materials have hitherto been the most practical in terms of temperature characteristics and dielectric constant. That is, it is excellent in that the temperature change of the pyroelectric coefficient is small and the dielectric constant is appropriately small. On the other hand, the lead zirconate titanate-based material can have a larger pyroelectric coefficient than the lead titanate-based material, but has a drawback in that it is inferior in terms of temperature characteristics and dielectric constant of the pyroelectric coefficient.
In recent years, ceramics have been invented that can be put to more practical use by improving pyroelectricity by substituting a part of Pb of this lead titanate-based material with Ca or La. For example, Japanese Patent Application No. 59-42920 and Japanese Patent Application No. 58-240192.
No.

[0003]

However, in the above-mentioned conventional technique, although the pyroelectric coefficient p can be improved, the dielectric constant ε also increases at the same time. That is, the figure of merit F = p / ε
Is about 20 to 25% of Pb at the A site of PbTiO ₃ which is an ABO ₃ type perovskite structure is replaced with at least one of Ca and La, for example, (Pb _0.75 Ca _0.25 ) TiO ₃ , (Pb
_0.75 Ca _0.20 La _0.05 ) TiO ₃ and (Pb _0.80 La _0.20 ) TiO ₃ show the maximum value in the composition, and when the substitution is 25% or more, it decreases. There is a limit to the improvement of the index.

The present invention has been made in view of the above,
An object of the present invention is to provide a pyroelectric porcelain composition having a good temperature characteristic of a pyroelectric coefficient, a small dielectric constant, and a large pyroelectric coefficient, in which a so-called figure of merit is improved.

[0005]

Means for Solving the Problems The pyroelectric porcelain composition of the present invention has a basic composition represented by the chemical formula (Pb _X La _{(2/3) y} Ca _z ) TiO _{3 in} which x, y and z are A part of Ti, which is in the range shown below and is a B site, contains (Ni _1/3 Nb _2/3 ), (Mg
_1/3 Nb _2/3 ), (Mn _1/2 Sb _1/2 ), (Zn _1/3 Nb _2/3 ), (Sn _w Sb
_1-w ) and (Cu _1/3 Nb _2/3 ) are substituted by at least one of them.

0.65 ≦ x ≦ 0.98 0.01 ≦ y ≦ 0.30 0.01 ≦ z ≦ 0.30 0 <w <1

[0007]

[Function] Obtained by substituting the A site of PbTiO ₃ with at least one of Ca and La (Pb _x La
A part of Ti, which is the B site of _{(2/3) y} Ca _z ) TiO ₃ , is converted into (Ni _1/3 Nb
_2/3 ), (Mg _1/3 Nb _2/3 ), (Mn _1/2 Sb _1/2 ), (Zn _1/3 Nb _2/3 ), (S
Pyroelectric properties can be improved by substituting at least one of (n _w Sb _1-w ) and (Cu _1/3 Nb _2/3 ).

[0008]

EXAMPLES Examples of the present invention are obtained by substituting the A site of PbTiO ₃ with at least one of Ca and La ₍ Pb _x La _{(2/3) y} Ca _z ) TiO _{3 and} B site. Part of Ti is (Ni _1/3 Nb _2/3 ), (Mg _1/3 Nb _2/3 ), (Mn _1/2 Sb
( _1/2 ), (Zn _1/3 Nb _2/3 ), (Sn _w Sb _1-w ), (Cu _1/3 Nb _2/3 ) and at least one of them. Is.

Next, a method of manufacturing the pyroelectric porcelain according to the present invention having the above structure will be described. The examples of the present invention are manufactured by a well-known manufacturing method using a solid phase reaction. The starting materials were high-purity PbO, La ₂ O ₃ , CaCO ₃ , and Ti, respectively.
O ₂ , SnO ₂ , Sb ₂ O ₃ and MnCO ₃ powder were used, and these raw materials were (Pb _X La _{(2/3) y} Ca _z ) {Ti _1-A (Sn _w Sb _1-w ) _A } O ₃ +0.5 wt% MnCO ₃ 0.65 ≦ x ≦ 0.98 0.01 ≦ y ≦ 0.30 0.01 ≦ z ≦ 0.30 0 <A <1 0 <w <1 Weighed and wet mixed.

These mixed powders were calcined at 800 ° C. to 900 ° C. for 2 hours and then wet pulverized to adjust the average particle size to about 0.5 μm. 4 wt% of 4cc per 100g of crushed powder
An aqueous PVA solution was added and passed through # 30 mesh to obtain granulated powder. A pressure of 1000 kg / cm ² is applied to this granulated powder to produce φ15 × 1.5 m
m pellets are molded and degreased at 400 ℃, then 1200 ℃ ~
The desired porcelain was obtained by firing at a temperature of 1250 ° C. for 2 hours. The obtained porcelain was polished to a thickness of 150 μm, silver was vapor-deposited on the polished surface, a pair of electrodes was applied, and polarization was performed at a voltage of 6 kv / mm to prepare a sample for measurement.

Table 1 shows the characteristics of various compositions in which a part of the B site is replaced with (Sn _w Sb _1-w ). However, sample No. 1 is sample No. 2 which is an example of the present invention.
A comparative example for comparison with Sample No. 7, which is A
When the sites are replaced by 25%, the performance indexes F _{1 and} F ₂ are the maximum values in the A site replacement. In addition, the B site is not replaced in the comparative example.

[0012]

[Table 1]

As is clear from Table 1, N is higher than that of sample No. 1 in which the figure of merit shows the maximum value only with A site substitution.
The characteristics were improved in o.4 and No.6. Particularly in No. 6, the figure of merit was improved by 5% for F _{1 and} 10% for F ₂ . Further, tan δ which is a cause of noise is 0.4 to 0.6, which can be suppressed to a small value. Further, the Curie point was 200 ° C. or higher, and good temperature characteristics of sensitivity could be obtained near room temperature.

A part of the B site is (Ni _1/3 Nb _2/3 ), (M
g _1/3 Nb _2/3 ), (Mn _1/2 Sb _1/2 ), (Zn _1/3 Nb _2/3 ), (Cu _1/3 Nb
For each of ( _2/3 ), the same figure of merit was obtained as when replaced with (Sn _w Sb _1-w ).

[0015]

As described above, the present invention has the chemical formula
(Pb _X La _{(2/3) y} Ca _z ) TiO ₃ part of the B composition of the basic composition is (Ni _1/3 Nb _2/3 ), (Mg _1/3 Nb _2/3 ), (Mn _1/2 S
b _1/2 ), (Zn _1/3 Nb _2/3 ), (Sn _w Sb _1-w ), (Cu _1/3 Nb _2/3 ).
Since it is configured to be replaced with at least any one of them, it is possible to greatly improve the performance index while keeping tan δ low. As a result, if a sensor is manufactured using the element according to the present invention, the S / N ratio can be made larger than in the conventional case, and a high-performance sensor can be provided.

Claims (1)

[Claims] 1. In the basic composition represented by the chemical formula (Pb _X La _{(2/3) y} Ca _z ) TiO ₃ , x, y, z are in the ranges shown below, and Ti of B site is included. part _{(Ni 1/3 Nb 2/3)} ,
(Mg _1/3 Nb _2/3 ), (Mn _1/2 Sb _1/2 ), (Zn _1/3 Nb _2/3 ), (Sn _w Sb
_1-w), pyroelectric ceramic composition characterized in that it is substituted by at least one of the _{(Cu 1/3 Nb 2/3)} . 0.65 ≦ x ≦ 0.98 0.01 ≦ y ≦ 0.30 0.01 ≦ z ≦ 0.30 0 <w <1