JPH0471028B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a fired pyroelectric porcelain body suitable as a sensing element such as an infrared sensor used to detect the approach of a person or animal, the presence or absence of an object, etc. PRIOR TECHNOLOGY Systems that can detect when a person or animal has invaded a specific area and notify the user of the intrusion have been used in, for example, a residence. An infrared sensor is used that can detect the emitted infrared rays.
Infrared sensors are also used for so-called non-contact temperature measurement, which detects infrared rays emitted by objects to determine their presence and movement. Such infrared sensors include quantum type sensors that utilize semiconductor photoconduction and photovoltaic force, such as
Products using HgCdTe and PbS are known,
These have good sensitivity and excellent responsiveness, but they have problems with handling as they need to be cooled to an extremely low temperature before use, and the sensitivity varies depending on the wavelength of the infrared rays, making them less versatile. Missing. On the other hand, a pyroelectric infrared sensor has been developed, and although it is inferior to the above sensors in terms of performance such as sensitivity, it is superior in that it does not require cooling and its sensitivity is not wavelength dependent. There is. The fired pyroelectric ceramic body used in this pyroelectric infrared sensor is an oxide with a composite perovskite structure represented by (Pb _1-x Ca _x )TiO ₃ (where x is a value between 0.1 and 0.4). MnO, _NiO , _Nb2O5
A fired body is known in which 0.01 to 2% by weight of one selected from the following is added and blended. Generally, the performance of a pyroelectric infrared sensor is determined by the evaluation index F _v = P/C _v・ε for the voltage generated by its pyroelectric effect.
(C・cm/J) [Here, P (C/cm ²・℃) is the pyroelectric coefficient, C _v (J/cm ³・℃) is the specific heat of constant volume, and ε is the dielectric constant]. However, if we apply the above-mentioned pyroelectric porcelain fired body to this, F _v = 3.5 to 5.5 (×
10 ^-11 C・cm/J), P=2~6(×10 ^-8 C/cm ²・
°C), ε=190 to 450. This pyroelectric infrared sensor is incorporated into an infrared detection device, but when soldering to a circuit board, the heat of the molten solder is transferred, so it is desired that the Curie temperature be high. The Curie point of the above fired pyroelectric porcelain body is 200
~400℃, especially at the highest evaluation index, F _v = 5.5 (×10 ^-11 C cm/J), P = 3.5 (×
10 ^-8 C/cm ² ·°C), ε=190, and its Curie point is 250°C. Problems to be Solved by the Invention In recent years, a large number of intelligent buildings have been constructed, and alarms to prevent illegal entry into the buildings have come into widespread use. However, alarm devices using the above-mentioned pyroelectric infrared sensors often malfunction. The main reason for this is that the infrared sensor inside the alarm device detects infrared rays and generates an alarm by increasing the sensitivity of the signal by several tens of decibels, which causes it to operate due to noise. be. In order to solve this problem, it is possible to increase the evaluation index F _v to increase the infrared detection ability so that the sensitivity of the alarm signal does not need to be increased. In addition to reducing the dielectric constant ε, it is desirable to make the Curie temperature higher than the heat of the solder when incorporating an infrared sensor. The object of the present invention is that the evaluation index _Fv is, for example, 6.0×
The object of the present invention is to provide a fired pyroelectric porcelain body which has a temperature of 10 ^-11 (C·cm/J) or higher and can have a Curie temperature of 250°C or higher. Means for Solving the Problems In order to solve the above problems, the present invention is expressed by the general formula xPbTiO ₃ −yCaTiO ₃ −zPbCu _1/3 Nb _2/3 O ₃ where x, y, and z are 0.55. ≦x≦0.79 0.22≦y≦0.35 0.01≦z≦0.10 (however, x+y+z=1) and for 100 mole parts of this oxide
A pyroelectric material containing 2 to 15 mole parts of NiSnO ₃ and 0.1 to 3.0 parts by weight of at least one of MnO ₂ and Cr ₂ O ₃ per 100 parts by weight of the NiSnO ₃ and the above-mentioned oxides. The present invention provides a fired porcelain body. Next, the present invention will be explained in detail. In the present invention, PbTiO ₃ −CaTiO ₃ −
Contains a ternary oxide of PbCu _1/3 Nb _2/3 O ₃ ,
The presence of PbCu _1/3 Nb _2/3 O ₃ increases the pyroelectric coefficient P, which makes it possible to increase _Fv . Furthermore, by increasing P, the Curie point can be increased to 250°C or higher. The proportions of each of the above oxides are as follows: PbTiO ₃ is 55 mol% or more and 79 mol% or less, CaTiO ₃ is 20 mol% or more and 35 mol% or less, PbCu _1/3 Nb _2/3 O ₃ is 1 mol% or more and 10 mol% If the usage ratio of PbCu _1/3 Nb _2/3 O ₃ is less than the lower limit of the above range or exceeds the upper limit of this range, F _v cannot be made 6 or more. Also,
When PbTiO ₃ is less than 55 mol%, the Curie point
The temperature will drop below 250℃. Such PbTiO ₃ −CaTiO ₃ −PbCu _1/3 Nb _2/3
NiSnO ₃ is added to the ternary oxide of O ₃ , which has the effect of lowering the relative dielectric constant ε, thereby increasing F _v
can be made even larger. Furthermore, at least one type of MnO ₂ and Cr ₂ O ₃ is used, that is, either one or both of them can be used, and by using these, the sinterability can be improved. The usage ratio is 0.1 to 3.0 parts by weight per 100 parts by weight of the above ternary oxide, and 0.1
If the amount is less, the sinterability will be poor and it cannot be used as a sensor element. Also, if it is more than 3.0,
This causes abnormal particle growth, resulting in F _v of less than 6.0 and poor pyroelectric effect. To produce the pyroelectric porcelain fired body of the present invention, the above-mentioned component powders are mixed using a pulverizing means such as an alumina pot mill. At this time, for example, the mixture may be wet-mixed with water, and after this mixing, dehydration and drying may be performed. After this, this mixture is heated for example at 800 to 900℃ for 1 to 2 hours.
After calcining for a time, the raw material powder may be ground by the above-mentioned grinding means, and this may be formed into a sheet by pressing, or the above-mentioned mixture may be mixed with a resin such as polyvinyl alcohol and granulated, and then this may be formed into a sheet. It's okay. Discs of a predetermined shape are punched out from these sheets, placed in a container made of magnesia, for example, and fired at, for example, 1100°C to 1250°C for 0.5 to 4 hours. Both sides of the obtained disc are polished. A metal such as silver is deposited to form a deposited film, and this is used as an electrode. In addition, for example, silver paste can be applied to the above sheet.
After drying and forming the electrode coating film, for example, 600 to 800
It may be baked at ℃. The fired body with electrodes formed thereon is immersed in an insulator such as silicone oil, subjected to a polarization treatment by applying a voltage for a certain period of time, and further subjected to an aging treatment. After this, for example, 3mm x 3
It is cut into square pieces of mm in size, and a pyroelectric infrared sensor is completed as an infrared detection element. When this pyroelectric infrared sensor is used by incorporating it into an alarm, for example, the polarization of the infrared detection element changes due to the heat of the infrared rays, generating a potential difference, which can be detected to determine the presence or absence of infrared rays and its intensity. . Examples Next, examples of the present invention will be described. Example 1 PbTiO ₃ 187.92g (62 mole parts), CaTiO ₃ 44.87g
(33 mole parts), PbCu _1/3 Nb _2/3 O ₃ 16.92g (5 mole parts), NiSnO ₃ 22.54g (10 mole parts), MnO ₂ 1.39g
(0.5% by weight) in a ball mill with 500ml of water.
The mixture was stirred and mixed for 20 hours, followed by dehydration and drying.
Add 20 parts by weight of a 10% by weight aqueous solution of polyvinyl alcohol to 100 parts by weight of this dried powder, granulate it with a press, form it into a disc with a diameter of 10 mm and a thickness of 0.5 mm, and heat it at 1100°C for 2 hours. By firing in the atmosphere, a ceramic substrate with a diameter of 8.5 mm and a thickness of 0.43 mm was obtained. This porcelain substrate was polished to a thickness of 0.2 mm, and silver paste was applied to both the front and back surfaces (100 parts by weight of silver powder to lead,
A composition containing 2 parts by weight of boron and silicon-based glass frit and 20 parts by weight of an organic vehicle containing a 9:1 mixture of butyl carbitol acetate and ethyl cellulose was applied and baked at 650°C for 10 minutes. 100 pieces of ceramic substrate with electrodes formed in this way
℃, polarized at 800V in silicone oil for 10 minutes, cut into 3mm square pieces using a cutter to create a pyroelectric infrared sensor, and measured the Kyrie point, as well as pyroelectric coefficient P and relative permittivity. ε was measured and F _v was calculated, and these are shown in Table 2. For calculations, C _v = 3.1 J/cm ³ ·°C was used. The measurement method is as follows. First, the relative dielectric constant ε is calculated using a formula from capacitance measurements based on JIS C-5102, and the Curie point is determined by examining the change in capacitance at each temperature level in a constant temperature bath, and finding the point with the highest capacitance. This was determined by searching for . Next, the pyroelectric coefficient P is equal to constant temperature rise 5 (°C/
Read the current value generated in minutes) with a picoammeter,
It was obtained by determining the change value in the range of 0 to 150°C. Examples 2 to 16 In Example 1, PbTiO ₃ , CaTiO ₃ ,
PbCu _1/3 Nb _2/3 O ₃ , NiSnO ₃ , MnO ₂ and/or
Infrared sensors were produced in the same manner except that Cr ₂ O ₃ was used in the proportions shown in Table 1, and they were treated in the same manner as in Example 1. The results of measuring and calculating each item are shown in Table 2. show. In addition, PbTiO ₃ , CaTiO ₃ ,
The composition of PbCu _1/3 Nb _2/3 O ₃ is shown in the triangular diagram in the figure in correspondence with each example number.

【table】

【table】

[Table] From the above results, it can be seen that all of the examples had an F _v of 6 or higher and a Curie temperature of 260° C. or higher. Effect of the invention According to the present invention, PbTiO ₃ −CaTiO ₃ −PbCu _1/3
NiSnO ₃ is added to the Nb _2/3 O ₃ system, and then MnO ₂ ,
Since it is possible to provide a fired ceramic body containing at least one type _of Cr ₂ O ₃ as a main component,
The evaluation index F _v is larger than that of the CaTiO ₃ type, and the detection sensitivity of infrared rays can be increased accordingly, so when this is used in an alarm, there is no need to increase the gain of the alarm signal, and the alarm will be affected by noise. can reduce malfunctions. Furthermore, the Curie temperature is 250°C or higher, which can be higher than the temperature during soldering, so it can be done without impairing its function as an infrared sensor.

[Brief explanation of the drawing]

The figure shows a fired pyroelectric porcelain body according to an embodiment of the present invention.
It is a triangular diagram showing the composition of three components: PbTiO ₃ , CaTiO ₃ , and PbCu _1/3 Nb _2/3 O ₃ . The numbers in the figure indicate the numbers of the examples.

Claims (1)

[Claims] 1 Represented by the general formula xPbTiO ₃ −yCaTiO ₃ −zPbCu _1/3 Nb _2/3 O ₃ , where x, y, and z are 0.55≦x≦0.79 0.20≦y≦0.35 0.01≦z≦0.10 (However, x + y + z = 1) For 100 moles of this oxide,
A pyroelectric material containing 2 to 15 mole parts of NiSnO ₃ and 0.1 to 3.0 parts by weight of at least one of MnO ₂ and Cr ₂ O ₃ per 100 parts by weight of the NiSnO ₃ and the above-mentioned oxides. Sexual porcelain fired body.