JPH0517149A - Lead titanate solid solution and sealing material using the same solid solution - Google Patents

Abstract

PURPOSE:To obtain a sealing material lowered in thermal expansion coefficient by mixing a lead titanate solid solution body obtained by replacing Pb of tetragonal PbTiO3 with a prescribed amount of Na and La with low-melting glass. CONSTITUTION:Pb of tetragonal PbTiO3 is replaced with Na and La at a ratio of Na and La of 14-40mol% and molar ratio of Na/La of 0.43-2.33 to provide lead titanate solid solution having low thermal expansion. The solid solution is mixed with low melting glass (e.g. PbO-B2O3 based, PbO-ZnO-B2O3 based or PbO-B2O3-ZnOSiO2 based glass) to provide a sealing material. The sealing material is utilized for sealing of electric component because of low thermal expansion coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low thermal expansion material and a material obtained by mixing the same with glass as a filler, and a sealing material suitable for sealing electronic parts such as semiconductor parts and fluorescent display tubes, and the like. It concerns a filler.

[0002]

2. Description of the Related Art Conventionally, Pb-substituted lead titanate solid solutions of tetragonal PbTiO ₃ have been well known as dielectric materials and piezoelectric materials. These are, for example, Pb _1/2 (Mg _1/3 Nb _2/3 ) _1/2 Ti
O ₃ ,, Pb (Zr _0.52 Ti _0.48 ) O ₃ , (Pb _0.94 Sr _0.06 ) (Zr _0.53 Ti _0.47 )
O _{3 and the} like have been proposed and have been mainly used as a polycrystalline sintered body for piezoelectric materials and the like.

Tetragonal PbTiO ₃ is used as a filler for low melting point sealing glass by utilizing its low thermal expansion property in addition to dielectric and piezoelectric materials. Low melting point sealing glass is PbO-ZnO-B ₂
O ₃ type is known, but generally, these glasses have a coefficient of thermal expansion of 90 × 10 ⁻⁷ / ° C. or more, and 80 × 10 ⁻⁷ /
It is unsuitable for sealing objects to be sealed below ℃. For this reason, it is necessary to bring the sealing glass close to the thermal expansion coefficient of the material to be sealed, and a sealing material in which a low thermal expansion material is mixed with a low melting point glass as a filler is mainly used.

Various types of low thermal expansion fillers have been proposed, and there are zircon, cordierite, willemite, mullite, β-eucryptite, β-spodumene, tin oxide, and lead titanate. The above is added to the low melting point glass and used.

Among the above-mentioned various fillers, lead titanate has a low coefficient of thermal expansion, and the effect of reducing the coefficient of thermal expansion of low-melting glass is great, and conventionally a sealing material using lead titanate or a solid solution thereof has been proposed. . For example, JP-A-62-256
741 is a sealing material using a filler in which a part of Pb of lead titanate is replaced by Ca. JP-A-2-30639 describes a part of Pb of lead titanate as Ca and Ti A sealing material has been proposed in which the parts are replaced with Fe and W.

[0006]

However, the lead titanate solid solution as the above-mentioned dielectric or piezoelectric material utilizes the electrical characteristics of the lead titanate solid solution and is used in the low melting point sealing glass. The solid solution has various problems when used as a sealing material. For example, JP-A-62-25674
The sealing material of 1 has a low coefficient of thermal expansion even when the particle size of the filler is small, but there is a problem that microcracks occur in the glass around the filler because the coefficient of thermal expansion of the filler is extremely small.

The sealing material of Japanese Patent Laid-Open No. 2-30639 proposes a sealing material that eliminates the occurrence of microcracks. However, a filler used for this sealing material, that is, a part of Pb of lead titanate is converted to Ca. , Using a lead titanate solid solution in which a part of Ti is replaced by Fe, W has a problem that the coefficient of thermal expansion is large. An object of the present invention is to provide a lead titanate solid solution having a thermal expansion lower than that of general lead titanate and a sealing material using the same, which has not been known.

[0008]

The present invention is directed to tetragonal PbTi
Provided is a lead titanate solid solution in which Pb of O ₃ is substituted with Na and La by 14 to 40 mol%, and a sealing material obtained by mixing the solid solution with lead titanate.

The lead titanate solid solution of the present invention has a tetragonal perovskite structure. The tetragonal perovskite structure is represented by PbTiO ₃ , but the lead titanate solid solution of the present invention is one in which Pb is replaced with Na and La. Specifically, it can be expressed as (Pb _X , Na _{(1-X) / 2} , La _{(1-X) / 2} ) TiO ₃ by a chemical formula, but it does not necessarily have to be this atomic ratio, and there is some deviation. Does not impair the characteristics.

The lead titanate solid solution of the present invention contains Pb as Na and
Although it is characterized in that it is replaced with La, the reason for limiting the Pb substitution amount to 40 mol% or less is that by further substitution, a by-product is generated without becoming a lead titanate solid solution,
This is because the effect of reducing the coefficient of thermal expansion is reduced, or a solid solution is formed, but the thermal expansion does not decrease. on the other hand,
When the amount of substitution is less than 14 mol%, the coefficient of thermal expansion increases, which is not preferable.

The lead titanate is manufactured as follows. A lead compound such as PbO, a titanium compound such as TiO ₂ , a lanthanum oxide compound, and a sodium compound such as sodium carbonate are mixed in an atomic ratio to be produced. Then, this is heated in the atmosphere at a temperature of 800 to 1000 ° C. to 0.5 to
Obtained by heating for 2 hours.

The Pb substitution amount of the lead titanate solid solution of the present invention is preferably 1 considering the effect of reducing the thermal expansion coefficient.
8 to 35 mol% is desirable. The ratio of Na and La to be replaced is
Considering the balance of charges, 1 is preferable, but 0.43 to 2.33
Within the range, the effect of lowering the coefficient of thermal expansion is not impaired.

The low thermal expansion lead titanate solid solution of the present invention is used as a sealing material with a filler. The low melting point glass is not particularly limited, and known ones can be used. Specifically, for example, PbO 40 to 90%, B ₂ O ₃ 8
PbO-B ₂ O ₃ -based consisting ~15%, PbO 70~85%, ZnO
0.5 ~7%, B ₂ O ₃ consisting of _{7~15% PbO-ZnO-B 2} O
₃ series, PbO 77-86%, B ₂ O ₃ 6-15%, ZnO 7-
A low melting point glass having a softening point of 400 ° C. or less, such as a PbO—B ₂ O ₃ —ZnO—SiO ₂ system composed of 12% and SiO ₂ 0.5 to 3% is preferably used.

[0014]

The lead titanate solid solution of the present invention is characterized in that Pb is replaced with Na and La to have a low thermal expansion as compared with general lead titanate. Although this mechanism of action is not always clear, it is considered to cause the following actions.
The lead titanate having a tetragonal perovskite structure has a-axis and b-axis.
The axes have the same length and the angles α, β and γ are 90 degrees. Pb is in the center of the lattice and Ti is in each vertex. It is considered that when Na, La, which has a short interatomic distance to oxygen, is substituted for Pb, the c-axis of the perovskite structure is significantly shortened and the following functions occur and the coefficient of thermal expansion decreases.

First, the bonds between the atoms become stronger, and atomic vibrations due to heat are less likely to occur. Secondly, strain is generated between the lattices, and it becomes difficult for the atomic vibrations due to heat to directly act to extend the lattices. Thirdly, the lattice constant of the substituted element does not become shorter as the ionic radius decreases, the gap between the atoms increases, and it becomes easier to allow atomic vibration due to heat. In any case, when the crystal is heated, the mechanism for increasing the entropy in addition to the increase in volume is further enhanced, so that the thermal expansion is lower than that of general lead titanate.

[0016]

【Example】

Example 1 Lead oxide, sodium carbonate, lanthanum oxide, and titanium oxide were weighed in predetermined amounts so as to have the compositions shown in Table 1, Sample Nos. 1 to 5,
After dry mixing, it was calcined at 1100 ° C for 2 hours. This calcined product was dry pulverized and further calcined at 1200 ° C. for 5 hours. The fired product thus obtained was dry-pulverized and passed through a 250-mesh sieve to have an average particle size of 5 to 6 μm. Table 1 shows the results of calculating the volume thermal expansion coefficient of the powder obtained here by determining the lattice constant using a powder X-ray diffractometer at temperatures of 30 ° C and 300 ° C. For comparison, ordinary lead titanate is shown in Sample No. 6 of Table 1 by the same method.

Example 2 Lead oxide, boron oxide, silicon oxide, aluminum oxide, and zinc oxide were weighed in predetermined amounts so as to have the composition shown in Table 2, dry-mixed, put in a platinum crucible and melted at 900 ° C. for 1 hour.
It was formed into a plate shape. This molded product was dry-ground and passed through a 150-mesh sieve.

Table 3 shows the coefficient of linear thermal expansion when a predetermined amount of the filler shown in Table 1 and the glass shown in Table 2 were mixed to form a sealing material. In Table 3, as for cordierite, magnesium oxide, aluminum hydroxide and silicon oxide were weighed so as to have a stoichiometric ratio of 2MgO · 2Al ₂ O ₃ · 5SiO ₂ and dry-mixed, and then placed in a platinum crucible at 1600 ° C. After being melted for 3 hours, it was formed into a plate. This molded product is dry crushed to 1200
The product was calcined at 8 ° C. for 8 hours, further pulverized, and passed through a 300 mesh sieve. Commercially available tin oxide is 3
What was passed through a 00 mesh sieve was used.

Β-eucryptite is lithium carbonate,
Aluminum hydroxide and silicon oxide are weighed so as to have a stoichiometric ratio of Li ₂ O · Al ₂ O ₃ · 2SiO ₂ and dry-mixed, and then at 1200 ° C for 3
It was used after being fired for a time, further crushed, and passed through a 300-mesh sieve. Zircon is obtained by weighing zirconium oxide and silicon oxide in a stoichiometric ratio of ZrO ₂ · SiO ₂ , dry-mixing, firing at 1400 ° C. for 12 hours, further pulverizing and passing through a 300-mesh sieve. used.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

As described above, since the lead titanate solid solution of the present invention has a low coefficient of thermal expansion, it is effective in reducing the coefficient of thermal expansion when used as a filler for various materials. In particular, the sealing material obtained by mixing the lead titanate solid solution of the present invention and the low melting point glass is suitable for sealing electronic parts because it has a great effect of lowering the thermal expansion coefficient.

Claims (4)

[Claims] 1. Pb of tetragonal PbTiO ₃ with Na and La of 14 to
A low-thermal-expansion lead titanate solid solution characterized by being substituted by 40 mol%. 2. In the low thermal expansion lead titanate solid solution,
The low thermal expansion lead titanate solid solution according to claim 1, wherein Na and La are in a molar ratio of Na / La = 0.43 to 2.33. 3. A sealing material obtained by mixing the lead titanate solid solution according to claim 1 and a low melting point glass. 4. Zircon, cordierite, willemite, mullite, β-eucryptite, as a filler,
A sealing material comprising at least one powder of β-spodumene and tin oxide, the low thermal expansion lead titanate solid solution according to claim 1 and a low melting point glass.