JP2011168480A - High-temperature glass solder and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass solder for high-temperature applications which can be processed at a soldering temperature of not more than about 1,100°C and can be used at an operating temperature to about 900°C after conclusion of the soldering process. <P>SOLUTION: The glass solder has a linear coefficient of thermal expansion (α<SB>(20-300)</SB>) in the temperature range of 20-300°C of 8×10<SP>-6</SP>-11×10<SP>-6</SP>K<SP>-1</SP>and contains, in mass%, 10 to <45% BaO, 0-25% SrO (20-65% of BaO+SrO), 10-31% SiO<SB>2</SB>, <2% Al<SB>2</SB>O<SB>3</SB>, 0-10% Cs<SB>2</SB>O, 0-30% RO, 0-30% R<SB>2</SB>O<SB>3</SB>and 0-20% RO<SB>2</SB>, wherein RO is an alkaline earth metal oxide; R<SB>2</SB>O<SB>3</SB>is an oxide such as B<SB>2</SB>O<SB>3</SB>; and RO<SB>2</SB>is an oxide such as TiO<SB>2</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to glass solders, in particular amorphous and partially crystallized glass solders and their use, which are particularly suitable for high temperature applications.

  Glass solders are usually used to bond particularly glass and / or ceramic parts to each other or to create a joint for electrically insulating the parts to metal parts. In the development of glass solder, its composition is often selected so that the thermal expansion coefficient of the glass solder approximately corresponds to the thermal expansion coefficient of the parts to be joined together in order to obtain a long-term stable joint. Compared to other joints, for example plastic joints, glass solder based joints have the advantage that they can produce a hermetic seal and can withstand relatively high temperatures.

  Glass solders are generally manufactured from glass powder that is often melted during the brazing operation and forms a joint under the action of heat with the parts to be joined. The brazing temperature is generally selected to correspond approximately to the hemisphere temperature of the glass, or may deviate from that temperature, usually by ± 20K. The hemispheric temperature can be measured by microscopy using a high temperature microscope. It characterizes the temperature at which specimens, which were initially cylindrical, melt together to form a hemispherical mass. The hemisphere temperature can be assigned a viscosity of approximately log η = 4.6, as can be understood from the relevant technical literature. When crystal-free glass is melted in the form of glass powder, cooled again and solidified, it can usually be remelted at the same melting point. In the case of a joint comprising a crystal free glass solder, this means that the operating temperature at which the joint can be provided for a long period of time must be below the brazing temperature. In fact, the operating temperature in many applications needs to be well below the brazing temperature. This is because the viscosity of the glass solder decreases with increasing temperature, and glass with a certain fluidity can be squeezed out of the joint at high temperature and / or high pressure, which can cause the bond to deteriorate. is there. For this reason, glass solders for high temperature applications usually need to have a brazing or hemispheric temperature that is well above the later operating temperature.

  One field of application of such glass solders is junctions in high temperature fuel cells that can be used, for example, as an energy source for automobiles or for supplying distributed energy. One important type of fuel cell is the SOFC (Solid Oxide Fuel Cell), which can have a very high operating temperature, for example up to about 1100 ° C. Junctions comprising glass solder are typically used for the manufacture of fuel cell stacks, i.e., joining a plurality of individual fuel cells so that one stack is formed. Such fuel cells are already known and continually improved. In particular, today's fuel cell development trends are generally towards lower operating temperatures. Some fuel cells can currently reach operating temperatures of less than 800 ° C., so brazing temperatures can be lowered and are desirable because of the low thermal stress on the SOFC components during the brazing process .

  An important role in fuel cell development is played by the glass solder, which is the subject of the following disclosure.

DE 19857057 C1 describes an alkali-free glass-ceramic solder having a thermal expansion coefficient α _(20-950) of 10.0 × 10 ⁻⁶ K ^{−1 to} 12.4 × 10 ⁻⁶ K ⁻¹ . The solder described therein contains 20-50 mol% MgO. Glasses with a high content of MgO are in fact highly susceptible to crystallization resulting in compounds that crystallize rapidly and to a high degree. In the case of such rapid and solid crystallization, it is difficult to ensure good wetting of the material joined by the glass solder. However, this is necessary in order to be able to provide a joint that optimally meets each requirement. Furthermore, the glass solder described in this document contains 40 to 50 mol% of SiO ₂ . However, increasing the content of SiO ₂ causes an increase in melting point and also an increase in brazing temperature.

Similarly, glass ceramic solders are described in US Pat. No. 6,532,769 B1 and US Pat. No. 6,430,966 B1. These are designed for a brazing temperature of about 1150 ° C. and contain 5-15 mol% Al ₂ O ₃ . Such high brazing temperatures are undesirable for modern fuel cells. This is because it exposes metallic substrate materials and other heat sensitive materials to an excessive extent.

DE 102005002435 A1 describes a composite solder consisting of an amorphous glass matrix and a crystalline phase. The glass matrix has a high content of CaO and MgO above 20% by weight, which results in a relatively high viscosity and high dielectric loss. Furthermore, the content of Al ₂ O ₃ is at least 10% by mass. Al ₂ O ₃ is usually used in glass solders for crystallization control, but it is also used to reduce the thermal expansion of the solder, so often the glass solder has a high thermal expansion. It is counterproductive when used to join materials.

DE 10122327 A1 is a glass solder composed of a BaO—CaO—SiO ₂ system having a thermal expansion coefficient α _(20-300) exceeding 11 × 10 ⁻⁶ K ⁻¹ , and ceramics and metals are also used in a high temperature range. It describes what is to be joined. In particular, when joining materials having an expansion coefficient α of less than 12 × 10 ⁻⁶ K ⁻¹ , for example ZrO ₂ ceramics having a thermal expansion of 10 × 10 ⁻⁶ K ⁻¹ , thermal stress as a result of poor conformity And this may reduce strength or even cause complete destruction of the joint. These glasses have a BaO content of up to 45-55% by weight. High BaO content may cause increased crystallization. Furthermore, the proportion of SiO ₂ is in the range of 35 to 45 wt%. Increasing the SiO ₂ content results in a decrease in thermal expansion and an increase in the required bonding temperature.

DE19857057 C1 US 6,532,769 B1 US 6,430,966 B1 DE102005002435 A1 DE10122327 A1

The object of the present invention is therefore to be able to work at a brazing temperature of about 1100 ° C. or less and not to be squeezed from the joint and / or to flow out of the joint at an operating temperature of up to about 900 ° C. after the brazing process. The linear thermal expansion α _(20-300) in the temperature range of 20 ° C. to 300 ° C. is in the range of 8 × 10 ⁻⁶ K ^{−1 to} 11 × 10 ⁻⁶ K ⁻¹ . Therefore, it is to provide a brazing glass which is compatible with both steel used in fuel cells and oxide ceramics, in particular ZrO ₂ and / or Al ₂ O ₃ ceramics.

［ＲＯは、ＭｇＯ、ＣａＯ、ＺｎＯ及びＢｅＯからなる群から選択される少なくとも１種のアルカリ土類金属酸化物であり、Ｒ₂Ｏ₃は、Ｂ₂Ｏ₃、Ｇａ₂Ｏ₃、Ｉｎ₂Ｏ₃、Ｙ₂Ｏ₃、Ｌａ₂Ｏ₃及びＤｙ₂Ｏ₃からなる群から選択される酸化物であり、かつＲＯ₂は、ＴｉＯ₂、ＺｒＯ₂及びＨｆＯ₂からなる群から選択される酸化物である］を含有するガラスソルダーによって解決される。 The object is a glass solder for high temperature applications having a thermal expansion coefficient α _(20-300) of 8 × 10 ⁻⁶ K ^{−1 to} 11 × 10 ⁻⁶ K ⁻¹ , based on oxides % By mass

[RO is at least one alkaline earth metal oxide selected from the group consisting of MgO, CaO, ZnO and BeO, and R ₂ O ₃ is B ₂ O ₃ , Ga ₂ O ₃ , In ₂ O. ₃ , an oxide selected from the group consisting of Y ₂ O ₃ , La ₂ O ₃ and Dy ₂ O ₃ , and RO ₂ is an oxide selected from the group consisting of TiO ₂ , ZrO ₂ and HfO ₂ It is solved by a glass solder containing

を含有する。 Preferred embodiments are as follows:
In the glass solder, in mass% based on oxide,

Containing.

In said glass solder, furthermore in each case up to 2% by weight on the basis of oxides of CrO and / or PbO and / or V ₂ O ₅ and / or WO and / or SnO and / or CuO and / or MnO and / or CoO and / or Sb ₂ O ₃ are contained.

  In the glass solder, it exists as an amorphous glass after the brazing operation.

  In the glass solder, after the brazing operation, the proportion of crystalline material is present as partially crystallized glass ceramic, which is 50% or less by mass based on oxide.

In the glass solder, the crystal phase is SrBa ₂ Si ₃ O ₉ and / or Ba _0.8 Sr _3.2 SiO ₃ and / or Ba _0.8 Sr _0.2 SiO ₃ and / or BaSi ₂ O ₅ and / or BaSiO ₃ , Ba ₂ SiO _4. And / or Ba ₄ Si ₆ O ₁₆ and / or Ba ₂ Si ₃ O ₈ and / or Sr ₂ MgSi ₂ O ₇ , preferably no tridymite.

  The glass solder has a hemispheric temperature of 820 ° C to 1100 ° C.

  The glass solder is used for the production of hot joints, in particular hot joints for fuel cells, exhaust gas sensors and / or spark plugs.

  The glass solder is used for producing a sintered body and / or a sheet having high heat resistance.

The glass solder is used to join high expansion steel and / or high chromium alloy and / or Al ₂ O ₃ and / or ZrO ₂ ceramic.

  Unless otherwise noted, all percentages shown below are based on oxide based mass.

According to the invention, the glass solder has a linear thermal expansion coefficient α _(20-300) of 8 × 10 ⁻⁶ K ^{−1 to} 11 × 10 ⁻⁶ K ⁻¹ . Glass solder of the present invention contains a less than 45% from 10% BaO, and SiO ₂ from 10% to 31%, and SrO of 25% Optionally, the Al ₂ O ₃ less than 2%. However, the proportion of BaO and SrO is selected such that the sum of BaO and SrO is from 20% to 65%. It has been found that the higher the content of these two components, the undesirably increased tendency of the glass solder to crystallize during the brazing operation. On the other hand, if the total content of BaO and SrO is less than 20%, the thermal expansion decreases to less than 8 × 10 ⁻⁶ K ⁻¹ , which is outside the required range. Furthermore, the inventor has found that the high Al ₂ O ₃ content of the glass solder can adversely affect its properties, in particular, the relatively high content leads to an increase in the melting and / or brazing temperature, and It was confirmed that the thermal expansion was reduced. Therefore, the Al ₂ O ₃ content is limited to less than 2% Al ₂ O ₃ according to the present invention.

  Furthermore, the glass solder according to the invention optionally contains at least one alkaline earth metal oxide RO selected from the group consisting of MgO, CaO, ZnO and BeO in an amount of up to 30%. The content of alkaline earth metal oxide RO can also control the crystallization characteristics of the glass solder. A further favorable effect is that the dielectric loss can be reduced by RO-containing glass. Furthermore, the melting point and glass transition temperature can be reduced by alkaline-earth metal oxides that network-transform. Since the RO content also leads to an increase in the coefficient of thermal expansion, it is a simple way to adapt the glass solder to the parts to be fused.

Furthermore, the oxide R ₂ O ₃ selected from the group consisting of B ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ and Dy ₂ O ₃ may optionally be present. Present in the glass solder of the invention in an amount of up to 30%. These components R ₂ O ₃ can also control the crystallization behavior of the glass solder during the brazing operation. At the same time, they can increase the glass forming temperature. When the glass forming temperature T _g increases, the temperature use of the glass solder is enhanced.

A further optional component is an oxide RO ₂ selected from the group consisting of TiO ₂ , ZrO ₂ and HfO _{2 in} an amount up to 20%. These oxides can serve in particular as nuclei for partial crystallization as desired in certain embodiments.

The glass solder of the present invention preferably does not contain TeO ₂ (except impurities). That is because the raw materials are particularly harmful to human health. This means that the TeO ₂ content of the glass solder according to the invention is preferably less than 0.3% by weight, particularly preferably less than 0.2% by weight.

However, the oxides RO, R ₂ O ₃ and RO ₂ must be present in the glass solder according to the invention in an amount in the range of more than 2% and up to 35%.

According to the present invention, the glass solder is low in alkali metal or alkali metal oxides Li ₂ O, Na ₂ O, K ₂ O. According to the invention, a total of less than 1% by weight of these indicated alkali metal oxides are present in the glass solder. The glass solder of the present invention particularly preferably (except for impurities) does not contain these indicated alkali metal oxides or Rb ₂ O and Fr ₂ O. Alkali metals are generally said to have an adverse effect on electrical insulation properties. Chemical resistance also decreases with increasing alkali metal content. However, the present inventors have found that even a relatively high content of Cs ₂ O does not adversely affect the insulating properties of the glass solder of the present invention. For this reason, up to 10% by weight of Cs ₂ O may be present in the glass solder of the present invention. In the glass solder of the present invention, Cs ₂ O preferably further replaces at least a certain proportion of B ₂ O ₃ without unacceptably degrading the chemical resistance of the glass solder. In a preferred embodiment, this means that the total content of Cs ₂ O and B ₂ O ₃ is 30% by mass or less. However, as a matter of course, the glass solder may not contain Cs ₂ O except for impurities.

  Additional additives are naturally possible and are also encompassed by the present invention. For the purposes of the present invention, the term glass solder is formed from an amorphous ground glass that is used as a brazing glass before the brazing operation and from the ground glass during the brazing operation. Including both materials that are glassy, partially crystallized, glass-ceramics or other forms that may exist.

In a preferred embodiment, the glass solder according to the invention contains up to 15% B ₂ O ₃ . The B ₂ O ₃ content not only has a positive influence on the crystallization behavior but also has a positive influence on the melting behavior and thus on the glass melting. The very high B ₂ O ₃ content, on the other hand, can adversely affect the chemical resistance. Furthermore, a B ₂ O ₃ content of more than 15% can lead to the evaporation of boron oxide from the glass solder, which is likewise undesirable. Together with the SiO ₂ content, the B ₂ O ₃ content can also promote the formation of stable glass to a large extent.

  The glass solder according to the invention preferably contains up to 5% CaO. The CaO content can likewise affect the crystallization of the glass solder during the brazing operation, but it is also possible to suppress the formation of unwanted crystalline phase tridymite due to the addition of CaO. .

  MgO with a content of up to 6% is likewise preferred. Higher content of MgO can lead to increased crystallization during the brazing operation, which can lead to increased melting temperature. This MgO content increases the spacing between sintering and flow to a value of> 300 ° C.

TiO _{2 with} a content of less than 10% is likewise preferred. A higher content of TiO ₂ can lead to increased crystallization, thus shifting the flow to higher temperatures.

In a further preferred embodiment, the glass solder of the invention is in each case up to 2% CrO and / or PbO and / or V ₂ O ₅ and / or WO and / or SnO and / or CuO and / or Or it contains MnO and / or CoO and / or Sb ₂ O ₃ . These components can contribute, for example, to improved wetting properties for various substrates. However, the glass solder of the invention is particularly preferably at least mostly free of PbO. That is, PbO is present in an amount of 1% by weight or less, and the glass solder of the present invention (except for impurities) very particularly preferably does not contain PbO.

Furthermore, impurities due to raw materials or refining agents such as As ₂ O ₃ and / or BaCl may be present in the glass solder according to the invention in an amount of up to 0.2% in each case.

  After the brazing operation, the glass solder of the present invention is preferably present as an amorphous glass. This means that the glass solder has substantially no crystalline region.

  However, in an alternative preferred embodiment, the glass solder of the present invention is a partially crystallized glass ceramic present as a glass ceramic in which the proportion of crystalline material is 50% or less of the total mass To do.

In these partially crystalline glasses, excessive crystallization or precipitation of unwanted crystal phases can be avoided by the addition of R ₂ O ₃ and RO. Excess crystallization during the joining operation results in an increase in viscosity and shifts the brazing temperature to a value above about 1100 ° C.

SrBa ₂ Si ₃ O ₉ and / or Ba _0.8 Sr _3.2 SiO ₃ and / or Ba _0.8 Sr _0.2 SiO ₃ and / or BaSi ₂ O ₅ and / or BaSiO ₃ and / or Ba ₂ SiO ₄ and / or Ba ₄ Si ₆ O ₁₆ and / or Ba ₂ Si ₃ O ₈ and / or Sr ₂ MgSi ₂ O ₇ are preferably formed as a crystalline phase. The formation of tridymite can be avoided by the addition of CaO.

  In the partially crystalline embodiment, the composition of the glass solder of the present invention is preferably set so that the glass solder crystallizes slowly. If it crystallizes very strongly, often sufficient wetting cannot be obtained. In particular, the brazing glass should generally be introduced at the location where it is to be brazed in an uncrystallized or partially crystallized form when producing a joint. This is because the temperature required to wet the parts to be fused is lower.

The present inventor has found that, in this embodiment in particular, the ternary BaO—SrO—SiO ₂ in which the crystalline phase SrBa ₂ Si ₃ O ₉ is precipitated becomes a eutectic. The mass ratio of the oxides BaO, SrO and SiO ₂ is selected such that the composition in terms of these three oxides is in the eutectic range described. It is thus possible to obtain a glass having a narrow temperature interval of less than 300 ° C. between sintering and flow.

  The glass solder according to the invention preferably has a hemispheric temperature of 820 ° C. to 1100 ° C. and can therefore be used for bonding at about this temperature. Due to this possible temperature range, the glass solder is also suitable for processing in the laser bonding method.

  The glass solder of the present invention is generally produced by melting its constituents in a conventional glass melting apparatus to form glass and subsequently milling it to form glass powder. The glass powder can be introduced into the joint, for example, in the form of a dispensable paste or in the form of a pre-sintered compact.

  Optimal strength of the joint is achieved when the thermal expansion of the solder is optimally matched with the material to be fused. Furthermore, no excessive stress is produced in the solder as a result of the change in the coefficient of thermal expansion due to the crystallization process. The glass solder according to the invention ensures this by inter alia avoiding unwanted crystal phases.

  The glass solder of the present invention is particularly suitable for high temperature durability joints due to its physical properties. For the purposes of the present invention, high temperature durability means a temperature range above about 650 ° C. Such a joint can be used particularly preferably in fuel cells, in particular in SOFCs (solid oxide fuel cells). One example of use in a fuel cell is to join individual SOFCs to form a single SOFC stack. Further fields of application are sensors in combustion devices such as automotive applications, marine engines, power plants, aircraft or space navigation. One preferred application is the use of the glass solder of the present invention for sensors in the exhaust system of a motor vehicle having an internal combustion engine.

  However, the glass solder of the present invention can also be used to produce a sintered body having high heat resistance.

  The manufacturing method of a sintered compact is fully known. In general, the starting materials of the glass solder of the present invention are mixed together in powder form, generally mixed with an organic binder, and compressed into the desired shape. Instead of the starting powder, it is also possible to mill the glass according to the invention previously melted and to mix it with the binder. The compressed glass binder body is then brought to the sintering temperature. In doing so, the binder burns out and the glass components can be sintered together at the sintering temperature. The resulting sintered bodies can then be brought into contact with the parts to be joined and joined and / or joined to them by a brazing operation.

  The use of a sintered body in brazing has the advantage that the sintered body is a molded member and can be manufactured in virtually any shape. For example, a frequently used shape is a hollow cylindrical shape, which is preferably hermetically sealed with a connection pin that is electrically insulated after brazing, introduced into the through opening of the metal part together with the electrical connection pin. Glass-metal lead-through can be obtained. Such glass / metal leadthroughs are used in many electrical components and are known to those skilled in the art.

  A further preferred use of the crystallized glass solder and / or composite material according to the invention is the production of sheets comprising the glass solder and / or the composite material. Such a sheet is similar to the sintered body described above, but can also be made sufficiently flexible. Shapes can be extracted from these and preferably used to join flat parts together.

  The invention will now be described by the properties of the glass solder according to the invention and with the aid of comparative examples.

  First, the brazing glass was melted in a glass melting apparatus. The following properties were measured for brazing glass commonly present in one block, at least one large piece.

Definition:
α _(20-300) Coefficient of linear thermal expansion in the range of 20 ° C. to 300 ° C. T _g glass transition temperature, or abbreviated transition temperature ST softening temperature; at this temperature, the logarithm of viscosity is 7.6.

  The composition of the brazing glass and their physical properties are summarized in Table 1.

  After characterization of the brazing glass, generally a powdery glass solder is produced from the brazing glass by a milling process. In this example, a powder with a particle size distribution having a D (50) of about 10 μm and a D (99) of less than 63 μm is provided from a fused brazing glass and can be dispensed by processing together with a binder Paste was obtained. The powder and binder were homogenized by a three roll mill. The binder is generally an organic substance such as nitrocellulose, ethylcellulose, or an acrylate binder. In general, there is no further effect on the properties of the crystallized glass solder, but it should be chosen so that it can be completely burned off during heating.

The thermal characterization of the glass solder is subsequently carried out with a high temperature microscope. For this purpose, cylindrical specimens are compressed from brazing glass or composite material into the powder form to be characterized and the specimens are heated on a ceramic table at 10 K / min. Changes in the shape of the specimen are observed, and the following features that can be assigned a specific viscosity generally occur with increasing temperature in the case of non-crystallized samples:
Start of sintering: At this temperature, the powder particles begin to fuse. As a result, the height of the specimen decreases. The logarithm of viscosity is about 10 ± 0.3.

Softening temperature: This temperature ST _K is characterized by the onset of the edge rounding of the test cylinder. The logarithm of viscosity is about 8.2.

  Spherical temperature: the logarithm of viscosity is about 6.1.

  Hemispheric temperature: The specimen has an approximately hemispherical shape at this temperature. The logarithm of viscosity is about 4.6 ± 0.1.

  Flow temperature: At this temperature, the height of the specimen is about 1/3 of the initial height. The logarithm of viscosity is about 4.1 ± 0.1.

Crystallization temperature _Tc : peak crystallization temperature measured by differential thermal analysis (DTA), exothermic reaction.

  The thermal properties of the glass solder measured using a high temperature microscope and their properties after crystallization are also summarized in Table 1.

  On the other hand, all Examples E1-E6 have the desired behavior according to the invention. These achieve hemispheric temperatures well below 1100 ° C. The hemispheric temperature is often also referred to as the sealing temperature. Thereby, the glass solder of the present invention is particularly suitable for the laser bonding method. This is because at relatively high process temperatures, the ceramic to be joined and / or sealed by the glass solder will be excited by the laser due to a change in optical properties (increased absorption coefficient), This is because an undesired sudden increase in temperature can occur.

  When laser irradiation is used for bonding, the areas to be bonded are generally heated very quickly, in which case crystallization is sufficiently suppressed. Stable binding can be obtained within a period ranging from seconds to minutes. Positive junction experiments were performed using a diode laser (output: 3 kW) with emission wavelengths of 808 nm and 940 nm. The starting glass was stirred as a powder with the liquid to form a suspension, applied to the parts to be joined and subsequently irradiated with a laser.

  The glass solder of the present invention has all the preferable characteristics according to the problems of the present invention. Brazing glass as an intermediate material can be produced by conventional melting methods with good melting properties and a melting temperature that is not too high. It has a thermal expansion in the desired range and also has a tendency to crystallize, which can be controlled as required. Its composition effectively suppresses the formation of undesired crystalline phases, thereby enabling long-term stable low stress joints. Since they do not contain alkali metals, the glass solders of the present invention have excellent electrical insulation properties even at high temperatures.

The glass solder of the present invention makes it possible to obtain joints that allow high operating temperatures above 900 ° C. at low processing temperatures from about 820 ° C. up to 1100 ° C. Furthermore, good wetting of the interconnector material allows long-term stable joints only after the introduction of solder, since there is no or slow partial crystallization. The glass solder according to the present invention is used to produce an airtight, high temperature stable electrically insulating joint between materials having a thermal expansion of 8 × 10 ⁻⁶ K ^{−1 to} 11 × 10 ⁻⁶ K ^−1. it can. Such materials are, for example, high expansion steels, high chromium alloys, and oxide ceramics, in particular ZrO ₂ .

In particular, bonding between ZrO ₂ and ZrO _2, and bonding between ZrO ₂ and other materials with high thermal expansion, ie high expansion alloys such as CFY, Durcolloy, Inconel or Crofer22APU Can be achieved.

Claims (10)

A glass solder for high temperature applications having a thermal expansion coefficient α _(20-300) of 8 × 10 ⁻⁶ K ^{−1 to} 11 × 10 ⁻⁶ K ⁻¹ , in mass% based on oxide,

[RO is at least one alkaline earth metal oxide selected from the group consisting of MgO, CaO, ZnO and BeO, and R ₂ O ₃ is B ₂ O ₃ , Ga ₂ O ₃ , In ₂ O. ₃ , an oxide selected from the group consisting of Y ₂ O ₃ , La ₂ O ₃ and Dy ₂ O ₃ , and RO ₂ is an oxide selected from the group consisting of TiO ₂ , ZrO ₂ and HfO ₂ Is a glass solder. In mass% based on oxide,

The glass solder according to claim 1, comprising: Furthermore, in each case up to 2% by weight on the basis of oxide, CrO and / or PbO and / or V ₂ O ₅ and / or WO and / or SnO and / or CuO and / or MnO and / or CoO, and / or containing Sb ₂ O _3, glass solder according to claim 1 or 2.   The glass solder according to any one of claims 1 to 3, wherein the glass solder exists as an amorphous glass after the brazing operation.   4. After brazing operation, the proportion of crystalline material is present as partially crystallized glass ceramic, which is not more than 50% by weight on the basis of oxides. Glass solder. The crystalline phase is SrBa ₂ Si ₃ O ₉ and / or Ba _0.8 Sr _3.2 SiO ₃ and / or Ba _0.8 Sr _0.2 SiO ₃ and / or BaSi ₂ O ₅ and / or BaSiO ₃ , Ba ₂ SiO ₄ and / or Ba _4. containing Si ₆ O ₁₆ and / or Ba ₂ Si ₃ O ₈ and / or Sr ₂ MgSi ₂ O _7, preferably not containing tridymite, glass solder according to claim 5.   The glass solder according to any one of claims 1 to 6, which has a hemispheric temperature of 820 ° C to 1100 ° C.   Use of the glass solder according to any one of claims 1 to 7 for the manufacture of hot joints, in particular hot joints for fuel cells, exhaust gas sensors and / or spark plugs.   The use which uses the glass solder of any one of Claim 1-7 in order to manufacture the sintered compact and / or sheet | seat which have high heat resistance. Use of the glass solder according to any one of claims 1 to 7 for joining high expansion steel and / or high chromium alloys and / or Al ₂ O ₃ and / or ZrO ₂ ceramics.