JP2789305B2 - Manufacturing method of lead germanate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lead germanate is used as the infrared sensor since it exhibits excellent pyroelectric chemical composition _{Pb 5 Ge 3-X Si X} O 11 x = 0~0.6 (P
b ₅ Ge ₃ O ₁₁ (hereinafter referred to as PGO).

[0002]

2. Description of the Related Art At present, a two-dimensional sensor using a pyroelectric material employs a method in which silicon for a signal transfer unit and a pyroelectric material for an infrared light receiving unit are separately prepared and connected by a metal column. However
However, in this method, the firing temperature of the pyroelectric material is high,
If an attempt is made to form a light receiving portion directly on a silicon chip, metal electrodes, diffusion layers, and the like in the chip will be destroyed. Therefore, PGO is directly placed on a semiconductor substrate such as silicon.
As a method for producing the thin film of 1) , 1) a sputtering method, 2) a vapor deposition method, 3) a spray pyrolysis method, and the like have been studied . However, Pero Bed Sukaito type oxide PGO becomes a film of mixed structure of pyrochlore structure or both not subjected to heat treatment of 600 to 700 ° C. metastable phase in a paraelectric, yet Pb by heat treatment of high temperature It is known that composition control becomes difficult due to evaporation and the like.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to
It shows good pyroelectricity with a dielectric constant more than twice that of the
Simple and easy to change composition and molding shape
Good quality pyroelectric ceramics suitable for mass production.
To provide a method for producing lead germanate that can be produced at a low price
is there.

[0004]

SUMMARY OF THE INVENTION The lead germanate of the present invention comprises
The production method contains germanium and lead using alcohol as a dispersion medium by hydrolyzing a raw material compound containing no chloride ion dissolved in alcohol to obtain a lead germanate-based ceramics thin film exhibiting excellent pyroelectricity. sol was prepared, obtained sol was shaped simultaneously with the gelling, firing a molded article formed gel at low temperatures 500 to 7 00 ° C. characterized.

[0005] as the starting compound for producing germanium, lead hydroxide in alcohol, organic acid salts of these metals, an inorganic acid salt (except chloride) or alkoxide are suitable. Used because the chloride, it is possible to use as a raw material, it chlorine crystallization temperature is increased there is a risk of remaining in the film when used is
Not preferred.

[0006] Examples of suitable lead germanate compounds as a raw material, germanium alkoxide (e.g. eth <br/> Kishido, isopropoxide, n- butoxide) and the like. Preferable specific examples of the raw material lead compound include lead acetate, lead nitrate, and lead isopropoxide. Silicon tetraethoxide (TEOS) is used as a silicon raw material. As the alcohol for dissolving these raw material compounds and then forming a sol, an appropriate alcohol can be arbitrarily selected depending on the type of the raw material compound. -Propanol, ethylene glycol, glycerin or 2- (2-ethoxyethoxy) ethanol.

When lead isopropoxide or lead acetate and germanium isopropoxide are used as raw materials, the rate of hydrolysis is high and the reaction with moisture in the air occurs. Therefore, weighing and mixing are performed in a dry nitrogen atmosphere.

The above-mentioned predetermined raw material was dissolved in 2- (2-ethoxyethoxy) ethanol as a solvent to prepare a coating solution.

When the prepared sol is left as it is, it gradually undergoes dehydration polycondensation and gels in a container, so that it is developed into a film before gelation. For example, the surface of a suitable substrate ( for example , a plate of soda glass, non-alkali glass, Pyrex glass, quartz glass, etc.) is uniformly coated by a method such as dip coating, spin coating, spraying, or ultrasonic spraying.

When the sol coated on the substrate is left for a long time or the water is gradually evaporated, the sol gels to form a soft film.

Therefore, the structure of the present invention is as follows:
is there. That is, the raw material compound dissolved in alcohol is hydrolyzed.
Lead and gel with alcohol as dispersion medium by decomposition
M (OH) ₂ and M '(O
H) The first to prepare the sol of ₄ (M = Pb, M '= Ge)
Step and gelation of the resulting sol and molding at the same time.
A second step, and forming the formed gel molded product from 500 to 7
And baking at 00 ° C.
Of Pyroelectric Ceramics as a Production Method for Lead Germanate
Having a configuration.

Alternatively, an organic acid salt as a raw material compound,
It is characterized in that there use an inorganic acid salt or an alkoxide,
It has a configuration as a method for producing lead germanate.

Alternatively, 2-propanol is used as the alcohol.
Knol, ethylene glycol, glycerin or 2-
The use of (2-ethoxyethoxy) ethanol is particularly important.
It has a configuration as a method for producing lead germanate.

[0014]

FIG . 1 is a diagram showing an X-ray diffraction analysis of a thin film prepared using germanium isopropoxide and lead acetate as a raw material with respect to each heat treatment temperature change (indicating the orientation from 450 ° C. in the C-axis direction). FIG. 2 shows the change in the dielectric constant and the loss angle of the lead germanate Pb ₅ Ge ₃ O ₁₁ thin film produced using the same raw material as in FIG. FIG. 3 shows the temperature dependence of the dielectric constant of the thin film prepared in FIG. Max. At about 180 ° C. peak indicates the Curie temperature.

[0015] After drying the gel film, to produce crystals of lead germanate and fired. Firing temperature required varies depending on the raw materials used, about 500 ° C. When using alkoxide as a raw material, in the case of using a portion acetate 600
° C., in the case of using a part nitrate is about 700 ° C.. Approximately 4 hours of calcination is required to produce sufficient crystals of lead germanate.

The thin film lead germanate ceramics obtained has a thickness of about 0.11 μm by one dip coating.
m, dipping, lifting, drying, baking at 400 ° C., and repeating this operation to obtain a film having an arbitrary thickness.

The spontaneous polarization value calculated from the hysteresis loop of the lead germanate thin films were carried out at 550 ° C. The calcination using only alkoxides as raw material 1.4μC / cm ^2, coercive field 45 kV / cm, a part of the lead for film using acetate, the spontaneous polarization value 1.2μC / cm ^2, the coercive electric field 65
kV / cm was obtained and the dielectric constant was about 180.

[0018] The lead germanate ceramic thin film can be used as an infrared sensor by taking advantage of its characteristics.

[0019]

EXAMPLE 1.906 g of lead acetate trihydrate was collected in a dry box in a nitrogen atmosphere, dissolved by adding 10 ml of 2- (2-ethoxyethoxy) ethanol, and the solution was heated to 140 ° C. Stir for 1 hr. 0.926 g of germanium isopropoxide was added to this solution, and 170
Prepare a coating solution by heating to 0 ° C. and stirring for 1 hr.

[0020] The solution and after cooling the coating solution at room temperature.

A glass substrate is immersed in the prepared sol and slowly pulled up at a speed of several cm per minute.

[0022] dipping and lifting, drying, baking 550 ℃ 1
A film thickness of about 1 μm can be obtained in each operation. When a thicker film is required, this operation is repeated to obtain an arbitrary thick film. The film thickness is exactly proportional to the number of operations.

According to the above manufacturing method, the chemical composition is Pb ₅ Ge
In _3-X Si _X O ₁₁ with increasing amount of Si dielectric constant is reduced, the Curie temperature can be reduced.

[0024]

As described above, the lead geminate of the present invention is
According to the preparation, this is used precise chemical composition control of the sol-gel method, a high homogeneity, shaping of the high, the low temperature of the process temperature, the method comprising the feature of ease of operation
And the lead as a raw material, in that the alkoxide or lead germanium was lead acetate, C-axis direction (in FIG. 1 [00 by a method of heating a solution shown in FIG. 1
2], [003], and [006] ) , and a lead germanate thin film exhibiting good pyroelectricity with a dielectric constant more than twice that of the existing method can be manufactured at a low temperature of about 550 ° C. .

The operation is simple, suitable for mass production because it is easy to change the composition and molded shape, makes it possible to inexpensively produce a pyroelectric ceramic having excellent quality.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in X of each of the thin films prepared using germanium isopropoxide and lead acetate as a raw material.
The figure which shows a line diffraction analysis. (From 450 ° C to C axis direction [00
2], [003] and [006]. )

FIG. 2 is a diagram showing a change in dielectric constant and loss angle of a lead germanate Pb ₅ Ge ₃ O ₁₁ thin film manufactured using the same raw material as in FIG. 1 depending on a firing temperature.

FIG. 3 is a diagram showing the temperature dependence of the dielectric constant of the thin film manufactured in FIG. Max. At about 180 ° C. peak indicates the Curie temperature.

Claims (3)

(57) [Claims] 1. M (OH) ₂ and M ′ of a hydroxide of a mixture of lead and germanium using alcohol as a dispersion medium by hydrolyzing a raw material compound dissolved in alcohol.
To adjust the sol _{(OH) 4 (M = P} b, M '= Ge)
A first step, a second step of gelling the obtained sol and simultaneously forming the same, and firing the formed gel molded product at 500 to 700 ° C.
A method for producing lead germanate of pyroelectric ceramics, comprising: a third step . 2. An organic acid salt, an inorganic acid salt,
Or claim 1 which comprises using an alkoxide
The method for producing lead germanate according to the above. 3. The method for producing lead germanate according to claim 1, wherein 2-propanol, ethylene glycol, glycerin or 2- (2-ethoxyethoxy) ethanol is used as the alcohol.