Glass powder, dielectric paste and thick film heating body

Abstract

The invention provides glass powder, dielectric paste and a thick film heating body. The glass powder is prepared from the following raw materials in percentage by weight: 15 to 40 percent of B2O3, 15 to 40 percent of MgO, 20 to 50 percent of CaO, 7 to 20 percent of SiO2 and 0.1 to 8 percent of glass powder additive, wherein the total weight of the raw materials of the glass powder is 100 percent. Based on the total weight of the dielectric paste being 100%, the dielectric paste comprises 55-80% of the glass powder, 0-5% of cobalt blue, 8-35% of an organic carrier, 3-15% of a diluent, 0.5-3% of an inorganic additive and 0.2-1% of an auxiliary agent. The invention also provides a thick film heating body prepared from the dielectric paste. A dielectric layer formed by the dielectric paste is compact, free of cracking, high in binding force with stainless steel, good in breakdown voltage resistance and excellent in electrical property.

Description

Technical Field

[0001] This invention relates to the field of heating element manufacturing technology, and in particular to a glass powder and dielectric slurry and a thick film heating element. Background Technology

[0002] The concept of thick film is mainly relative to thin film. Thick film refers to a film layer with a thickness of several micrometers to tens of micrometers formed on a substrate using printing and sintering technology. The material used to manufacture this film layer is called thick film material. Thick film heating elements have many advantages, such as high power density, fast heating speed, high operating temperature, fast heating rate, high mechanical strength, small size, convenient installation, uniform heating temperature field, long life, energy saving and environmental protection, and safety.

[0003] In today's era of advocating energy conservation and environmental protection, this new type of safe, environmentally friendly, and high-performance heating element has gained widespread attention and application across various industries, gradually replacing traditional heating methods. Thick-film heating elements primarily rely on thick-film screen printing technology, sequentially printing insulating media, heating resistors, conductor materials, and protective media onto the heating element substrate, followed by high-temperature sintering. Stainless steel, with its excellent resistance to mechanical and thermal shock, moderate cost, and ease of processing, has become an ideal choice for substrates in high-power thick-film circuits.

[0004] CN101419850A mentions that the microcrystalline glass powder is composed of SiO2, B2O3, Al2O3, BaO, CaO, MgO, ZrO2, Co2O3, and TiO2. It is a high-barium system microcrystalline glass with BaO as the main component. The addition of Ba increases the coefficient of thermal expansion, and the precipitation of Ba-dominant crystals improves mechanical strength, thermal shock resistance, and breakdown strength. However, the Ba crystal form precipitated in this scheme is of various types, including h-BaAl2Si2O8 (coefficient of thermal expansion 8 ppm / ℃) and Celsian-BaAl2Si2O8 (coefficient of thermal expansion 2.3 ppm / ℃). The precipitated crystal phase is difficult to control, and the crystal form will change at different temperatures, resulting in a large change in the coefficient of thermal expansion. This causes a mismatch in the coefficients of thermal expansion between the glass and stainless steel, leading to cracking of the coating due to the mismatch in thermal expansion. Furthermore, the patent does not provide information on the coefficient of thermal expansion of the glass or the corresponding coating quality testing. Existing dielectric slurries for thick films do not consider the matching of thermal expansion coefficients with stainless steel, and are mainly used with SUS304, SUS316, and SUS430 stainless steel, lacking research on dielectric slurries that match the thermal expansion coefficient of SUS630 stainless steel. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a glass powder and dielectric slurry, and a thick-film heating element. The dielectric slurry forms a dense, crack-free dielectric layer with strong adhesion to stainless steel, good breakdown voltage resistance, and excellent electrical properties.

[0006] To achieve the above objectives, the present invention provides a glass powder, wherein the raw materials of the glass powder, based on the total weight of the raw materials of the glass powder as 100%, include: 15-40% B2O3, 15-40% MgO, 20-50% CaO, 7-20% SiO2, and 0.1-8% glass powder additives.

[0007] In the above glass powder, the sum of the weights of all raw materials can be 100%.

[0008] In the aforementioned glass powder, the glass powder additives generally include inorganic oxides. Specifically, the glass powder additives include one or more combinations of Fe2O3, Al2O3, ZrO2, La2O3, and SrO.

[0009] In the aforementioned glass powder, based on the total weight of the glass powder raw materials as 100%, the glass powder raw materials include 0.1-8% glass powder additives, and further include 1-4% glass powder additives. That is, based on the total weight of the glass powder as 100%, the glass powder raw materials include: B2O3 15-40%, MgO 15-40%, CaO 20-50%, SiO2 7-20%, and glass powder additives 0.1-8% (further 1-4%), and the sum of the weights of the above raw materials can be 100%.

[0010] According to a specific embodiment of the present invention, the weight percentage of B2O3 in the raw materials of glass powder can be 15-40%, for example, specific values ​​such as 15%, 20%, 25%, 30%, 35%, 40%, etc., and a range with any two of the above specific values ​​as endpoints.

[0011] According to a specific embodiment of the present invention, the weight percentage of MgO in the raw material of glass powder can be 15-40%, for example, specific values ​​such as 15%, 20%, 25%, 30%, 35%, 40%, etc., and a range with any two of the above specific values ​​as endpoints.

[0012] According to a specific embodiment of the present invention, the weight percentage of CaO in the raw materials of glass powder can be 20-50%, for example, specific values ​​such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., and a range with any two of the above specific values ​​as endpoints.

[0013] According to a specific embodiment of the present invention, the weight percentage of SiO2 in the raw material of glass powder can be 7-20%, for example, 7%, 10%, 15%, 20%, etc., and a range with any two of the above specific values ​​as endpoints.

[0014] In the above glass powder, the weight ratio of B2O3, SiO2, MgO and CaO can be further controlled as (15-25):(7-10):(35-40):(35-50).

[0015] According to a specific embodiment of the present invention, the weight percentage of the glass powder additive in the raw material of the glass powder can be 0.1-8%, for example, specific values ​​such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, etc., and a range with any two of the above specific values ​​as endpoints, further being 1-4%.

[0016] In some specific embodiments, the raw material of the glass powder does not contain the alkaline earth metal element Ba. This invention has found that the presence of Ba affects the average coefficient of thermal expansion of the glass powder. A difference of more than 10% between the average coefficient of thermal expansion and that of stainless steel can lead to defects such as cracks after sintering of the dielectric coating, thus affecting the quality and performance of the printed and sintered coating, and consequently impacting the adhesion to stainless steel, the pressure resistance, wear resistance, and electrical resistance of the dielectric coating.

[0017] In some specific embodiments, the glass powder can be obtained by hot melting of glass powder raw materials. In some specific embodiments, the hot melting temperature can be 1300-1400℃.

[0018] In some specific implementations, the glass powder may be microcrystalline glass powder.

[0019] In some specific embodiments, the particle size D50 of the glass powder is 1.0-6.5 μm, further can be 1.5-5.0 μm, and even further can be 2.0-4.0 μm.

[0020] In some specific embodiments, the particle size D100 of the glass powder is less than or equal to 40.0 μm; further, the particle size D100 of the glass powder can be less than or equal to 37 μm, for example, 30-37 μm.

[0021] In some specific embodiments, the glass transition temperature (Tg) of the glass powder is 580-680℃.

[0022] In some specific embodiments, the average coefficient of thermal expansion (CTE) of the glass powder at 50-400°C is 10ppm / °C-12ppm / °C; further, it can be 10.5ppm / °C-12ppm / °C; and even further, it can be 11ppm / °C-12ppm / °C.

[0023] In some specific embodiments, the glass powder matches the average coefficient of thermal expansion of SUS630 stainless steel, and the difference between the average coefficient of thermal expansion of the glass powder and SUS630 stainless steel is less than or equal to 10% of the average coefficient of thermal expansion of SUS630 stainless steel, wherein the average coefficient of thermal expansion of SUS630 stainless steel at RT (room temperature) - 400°C is 11.3 ppm / °C.

[0024] The present invention provides a media slurry, which, based on the total weight of the media slurry (100%), comprises: 55-80% of the glass powder provided by the present invention, 0-5% of cobalt blue, 8-35% of the organic carrier, 3-15% of the diluent, 0.5-3% of the inorganic additives, and 0.2-1% of the auxiliary agents.

[0025] In the above-mentioned medium slurry, the weight percentage of glass powder in the medium slurry is generally 55-80%, specifically 55%, 60%, 65%, 70%, 75%, 80%, etc., and a range with any two of the above specific values ​​as endpoints, for example, 65-80%.

[0026] In the aforementioned media slurry, cobalt blue is used to adjust the color. The weight percentage of cobalt blue in the media slurry can be 0-5%, specifically 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., or a range with any two of the above specific values ​​as endpoints. Cobalt blue is optional; when the media slurry contains cobalt blue, the weight percentage of cobalt blue in the media slurry can be greater than 0 and less than or equal to 5%.

[0027] In the above-mentioned medium slurry, the weight percentage of the organic carrier in the medium slurry can be 8-35%, specifically 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, etc., and a range with any two of the above specific values ​​as endpoints, for example, 8-25%.

[0028] In the above-mentioned medium slurry, the weight percentage of the diluent in the medium slurry can be 3-15%, specifically 3%, 5%, 7%, 9%, 10%, 11%, 13%, 15%, etc., and a range with any two of the above specific values ​​as endpoints, for example, 7-10%.

[0029] In the above-mentioned media slurry, the inorganic additive can account for 0.5-3% of the weight of the media slurry, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc., and a range with any two of the above-mentioned specific values ​​as endpoints, for example, 0.5-2.5%.

[0030] In the above-mentioned medium slurry, the weight percentage of the additive in the medium slurry can be 0.2-1%, specifically 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc., and a range with any two of the above specific values ​​as endpoints, for example, 0.4-0.9%.

[0031] In the aforementioned slurry, the organic carrier comprises a resin and a solvent. The resin comprises one or a combination of two or more of ethyl cellulose resin, cellulose acetate butyrate resin, and acrylic resin. The solvent comprises one or a combination of two or more of butyl carbitol acetate, terpineol, DBE (divalent ester), and butyl carbitol. The solvent is capable of adjusting the viscosity and solubility of the organic carrier.

[0032] In the above-mentioned medium slurry, the weight ratio of the resin to the solvent can be (13-35):(65-81), for example, (29-27):(73-81).

[0033] In the above-mentioned medium slurry, when the resin includes a combination of ethyl cellulose resin, cellulose acetate butyrate resin and acrylic resin, the weight ratio of the ethyl cellulose resin, cellulose acetate butyrate resin, acrylic resin and solvent is (8-20):(3-8):(2-7):(65-81), for example (8-20):(3-8):(2-7):(65-80), and may further be (9-16):(3-8):(3-6):(73-81) or (9-16):(3-8):(3-6):(73-80).

[0034] In the above-mentioned medium slurry, the diluent includes one or more of terpineol, butylcarbidol, benzyl alcohol, and dimethyl adipate.

[0035] In the above-mentioned medium slurry, the inorganic additives include one or more of titanium dioxide, copper oxide, nickel oxide, zirconium oxide, and lanthanum oxide.

[0036] In the aforementioned slurry, the additives include thixotropic agents and dispersants. Specifically, the thixotropic agents include one or more combinations of Thixatrol MAX (specifically, THIXATROL MAX solvent-based rheology modifier), CRAYVALLACMT, and organobentonite; the dispersants include one or more combinations of SC-1015F (Niko SC-1015F), 211P (Niko 211P), and AFB-1521 (Niko AFB-1521).

[0037] In the above-mentioned media slurry, when the additives contain multiple components, the proportions between the components can be adjusted according to the characteristics of the required media slurry.

[0038] The dielectric paste provided by this invention can be used as an insulating dielectric paste for thick-film heating elements on stainless steel substrates. In some specific embodiments, this dielectric paste can be applied to the surface of SUS630 stainless steel.

[0039] The dielectric slurry provided by this invention adjusts the glass powder formulation so that the glass powder has an average coefficient of thermal expansion that matches that of SUS630 stainless steel (generally, a difference of less than 10% between the two coefficients of thermal expansion is considered a match, and the smaller the difference, the better). Therefore, the finished product prepared by sintering will not have cracks. Furthermore, the average coefficient of thermal expansion of the glass powder in this dielectric slurry after melting matches that of the stainless steel. Therefore, when the dielectric slurry is printed on the stainless steel surface and sintered (850℃-930℃), the resulting dielectric layer has a matching average coefficient of thermal expansion with the stainless steel, and the adhesion between the dielectric layer and the stainless steel is excellent.

[0040] The above-mentioned medium slurry provided by the present invention can improve the adhesion between the medium slurry and the upper and lower layers after sintering by adjusting the composition of inorganic additives and their addition ratio in the medium slurry.

[0041] The above-mentioned medium slurry provided by the present invention can adjust the printability of the slurry by adjusting the proportions of glass powder, additives (including dispersants, thixotropic agents, etc.), organic carriers (including resins and solvents), diluents, inorganic additives, etc., so that the slurry has excellent printability; the printed graphics have good flatness and non-diffusion properties.

[0042] The present invention also provides a thick film heating element, the raw material of which includes the above-mentioned dielectric slurry provided by the present invention.

[0043] In some specific embodiments, the substrate of the thick-film heating element is made of SUS630 stainless steel, and the surface of the substrate has a dielectric layer formed by sintering the dielectric paste. In some specific embodiments, the thickness of the dielectric layer is greater than or equal to 50 micrometers.

[0044] In some specific embodiments, the thick-film heating element may further include a resistive coating and a conductive coating. The resistive coating is disposed on the surface of the dielectric layer; the conductive coating is disposed on the surface of the resistive coating; that is, the conductive coating, the resistive coating, the dielectric layer, and the substrate are stacked sequentially.

[0045] The beneficial effects of this invention include:

[0046] The glass powder in the dielectric slurry of this invention has an expansion coefficient that matches that of SUS630 stainless steel. The sintered dielectric layer will not crack and possesses advantages such as dense structure, high breakdown voltage, strong adhesion to stainless steel, and excellent electrical properties. Furthermore, this dielectric slurry exhibits excellent printability, producing printed patterns with good flatness and non-diffusion characteristics. The dielectric slurry provided by this invention can be used to produce SUS630 stainless steel thick-film heating devices. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the structure of the thick film heating element before encapsulation in this invention.

[0048] Key symbols: 1. Thick film heating element; 2. Dielectric layer; 3. Resistor coating; 4. Conductor coating. Detailed Implementation

[0049] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0050] Example 1

[0051] This embodiment provides a medium slurry, the preparation method of which includes:

[0052] Step 1) Preparation of glass powder

[0053] Preparation of glass powder: According to the raw materials and proportions shown in Table 1, B2O3, SiO2, MgO, CaO and glass powder additives are mixed evenly, heated and melted at 1300-1400℃ (see “Melting Temperature” in Table 1 for specific temperature values), cooled, ball-milled and sieved to obtain glass powder. The particle size D50 of the glass powder is 2.4-3.2μm (see “Particle Size D50” in Table 1 for specific values).

[0054] Step 2) Preparation of organic carrier:

[0055] According to the raw materials and proportions shown in Table 1, ethyl cellulose resin, cellulose acetate butyrate resin, and acrylic resin were added to a solvent (at least one of butyl carbitol acetate, terpineol, DBE, and butyl carbitol), and completely dissolved under constant temperature of 80°C. After keeping at this temperature for 2 hours, the organic carrier was obtained by filtration through a 250-mesh standard sieve.

[0056] Step 3) Preparation of media slurry

[0057] According to the raw materials and proportions shown in Table 1, the glass powder prepared in step 1), the organic carrier prepared in step 2), the inorganic additives, the diluents and the auxiliary agents are mixed evenly, dispersed using a ceramic three-roll mill, the particle size is dispersed to below 10μm, the viscosity is adjusted to a suitable level, and the medium slurry is obtained by filtration.

[0058] Examples 2 to 5

[0059] Examples 2 to 5 provide media slurries, and the preparation method of the media slurries is the same as that of Example 1. The raw materials and proportions of the media slurries are shown in Table 1.

[0060] Table 1 shows the composition of the slurry raw materials for Examples 1 to 5 (addition amounts are by weight). The weight content of glass powder, cobalt blue, organic carrier, diluent, inorganic additives, and auxiliaries refers to the weight percentage of the above components in the slurry raw materials. In Table 1, the percentage of each raw material in glass powder represents the weight percentage of that component in the glass powder raw material; the percentage of each component in the organic carrier represents the weight percentage of that component in the organic carrier. The values ​​of each component in diluent, inorganic additives, and auxiliaries represent the weight percentage of that component in the medium slurry.

[0061] For example, the composition of the medium slurry in Example 1 is as follows:

[0062] Based on the total weight of the slurry as 100%, it includes 73% glass powder, 1% cobalt blue, 15.4% organic carrier, 7.6% diluent, 2.5% inorganic additives and 0.5% auxiliary agents;

[0063] The glass powder raw materials, based on a total weight of 100%, include 35.00% B2O3, 20.00% MgO, 37.00% CaO, 7.00% SiO2, and 1.00% La2O3.

[0064] Based on the total weight of the organic carrier as 100%, the organic carrier includes 16.00% ethyl cellulose, 8.00% cellulose acetate butyrate, 3.00% acrylic resin, 30.00% butyl carbitol acetate, 15.00% terpineol, and 28.00% butyl carbitol;

[0065] Based on the total weight of the slurry as 100%, the diluent includes 4.6% benzyl alcohol, 2% butyl carbitol, and 1% dimethyl adipate; the inorganic additives include 1% La2O3, 0.5% TiO2, and 1% ZrO2; and the auxiliary agents include 0.2% Thixatrol MAX and 0.3% Nippon Oil AFB-1521.

[0066] Table 1

[0067]

[0068] Table 1 (below)

[0069]

[0070] According to a specific embodiment of the present invention, the dielectric slurry of the present invention (including the dielectric slurries prepared in Examples 1 to 5) can be used to prepare a thick-film heating element, and the preparation method of the thick-film heating element can be specifically as follows:

[0071] The substrate (generally a stainless steel substrate, such as SUS630 stainless steel) is cleaned, and the dielectric paste of the present invention is printed on the surface of the substrate. The dielectric paste is dried and sintered to obtain an insulating dielectric layer 2 (also known as an insulating dielectric layer).

[0072] A resistive paste is printed on the surface of the dielectric layer 2, dried, and sintered to form a resistive coating 3; a conductor paste is printed on the surface of the resistive layer, dried, and sintered to form a conductor coating 4. After encapsulation, a thick-film heating element 1 is obtained. Figure 1 This is a schematic diagram of the structure of a thick-film heating element before encapsulation. The thick-film heating element 1 includes a substrate, a dielectric layer 2, a resistive coating layer 3, and a conductor coating layer 4, which are stacked sequentially.

[0073] Comparative Example 1

[0074] This Comparative Example 1 provides a dielectric slurry comprising high-barium glass powder, cobalt blue, an organic carrier, a diluent, inorganic additives, and auxiliaries. By weight, the glass powder composition is as follows: 21.8 parts SiO2, 7.5 parts B2O3, 6.9 parts Al2O3, 36.9 parts BaO, 8.1 parts CaO, 7.5 parts MgO, 5.6 parts ZrO2, 3.8 parts Co2O3, and 1.9 parts TiO2. The remaining components of the dielectric slurry (cobalt blue, organic carrier, diluent, inorganic additives, and auxiliaries) are consistent with those of Example 1. The weight ratio of glass powder to the remaining components is 73:27. The weight ratios of cobalt blue, organic carrier, diluent, inorganic additives, and auxiliaries in the remaining components are the same as in Example 1. The preparation method of this slurry is similar to that of Example 1, except that the above-mentioned components of this Comparative Example are used to prepare the dielectric slurry.

[0075] The average coefficient of thermal expansion of the glass powders prepared in each embodiment and comparative example was tested, and the test results are shown in Table 2.

[0076] The average coefficient of thermal expansion (CTE) and glass transition temperature (Tg) in Table 2 were obtained by testing with a German Lindsay DIL L75H horizontal thermal expansion apparatus. The sample preparation method was as follows: high-temperature molten glass was poured into a low-temperature mold, annealed at 550℃ for 30 minutes, and then polished with a polishing machine to make both ends flat and the length 20-50mm before the average coefficient of thermal expansion was tested.

[0077] Table 2

[0078]

[0079] Table 3 shows the preparation methods of the samples to be tested:

[0080] The above-mentioned medium slurry was printed on a SUS630 stainless steel substrate by screen printing. After drying at 150°C for 10 minutes, it was sintered in a belt sintering furnace at 850°C±10°C with a peak holding time of 10~30 minutes to prepare test samples and conduct performance tests.

[0081] The preparation method of the test samples in Table 4 is as follows: Based on the test samples in Table 3, a resistive coating (ESL R314-A) and an electrode layer (i.e., a conductor coating, ESL 9693-S) are sequentially printed on the surface of the dielectric layer to form the test sample. The method for printing the resistive layer and the electrode layer is described in the corresponding steps of the preparation method of thick film heating elements.

[0082] The breakdown voltage was tested according to GB1408.1-2016 "Electrical strength test method for insulating materials - Part 1: Test at power frequency".

[0083] Sintered surface morphology: The surface state of the sintered film of the obtained sample was observed by magnification of 50x under a microscope.

[0084] Scratch resistance test: Tested according to GB / T 6739-2006.

[0085] Table 3 shows the performance results of the media slurry in Examples 1 to 5 and Comparative Example 1.

[0086] Table 3

[0087]

[0088] Table 3 shows that the dielectric slurry containing BaO in the glass powder of Comparative Example 1 developed surface cracks, had low breakdown voltage, and was not scratch-resistant after sintering; while the dielectric slurries of the various embodiments of the present invention have higher surface smoothness and density, and higher breakdown voltage and scratch resistance compared to the dielectric slurry of Comparative Example 1.

[0089] Table 4 shows the matching performance results of the dielectric slurry and electrode slurry in Examples 1 to 5 and Comparative Example 1, used to evaluate the bonding force between the dielectric layer and the electrode. The welding tensile force was determined according to GB / T 10410-2008 standard, and the volume resistivity was calculated using the volume resistivity formula.

[0090] Table 4

[0091]

[0092] As shown in Table 4, compared with Comparative Example 1, the dielectric slurry provided in the embodiments of the present invention has higher welding tensile strength and lower volume resistivity.

[0093] The results above show that the dielectric slurry in Comparative Example 1, due to the presence of barium oxide in the glass powder, exhibits a significant decrease in its average coefficient of thermal expansion after crystallization, which does not match the coefficient of thermal expansion of SUS630 (11.3 ppm / ℃). This results in cracking of the coating after sintering and low breakdown strength. In contrast, the dielectric slurry provided in this embodiment of the invention has a high match with the coefficient of thermal expansion of SUS630, resulting in a coating that remains intact and crack-free after sintering, high breakdown strength, strong scratch resistance, and improved electrical performance.

[0094] The above results demonstrate that the dielectric slurry provided by this invention, when applied to SUS630 stainless steel thick-film heating devices (thick-film heating elements), forms a dense, crack-free dielectric layer with strong adhesion to stainless steel and high breakdown voltage resistance; it also exhibits good adhesion to electrode slurry and excellent electrical performance.

Claims

1. A glass powder, wherein, Based on the total weight of the raw materials of the glass powder as 100%, the raw materials of the glass powder include: B2O3 15-40%, MgO 15-40%, CaO 20-50%, SiO2 7-20%, and glass powder additives 0.1-8%.

2. The glass powder according to claim 1, wherein, The glass powder additive includes one or more of Fe2O3, Al2O3, ZrO2, La2O3, and SrO.

3. The glass powder according to claim 1, wherein, The weight ratio of B2O3, SiO2, MgO, and CaO is (15-25):(7-10):(35-40):(35-50).

4. The glass powder according to claim 1, wherein, The particle size D50 of the glass powder is 1.0-6.5 μm, and the particle size D100 of the glass powder is less than or equal to 40.0 μm; Preferably, the glass powder has a particle size D50 of 1.5-5.0 μm; More preferably, the glass powder has a particle size D50 of 2.0-4.0 μm.

5. The glass powder according to claim 1, wherein, The glass transition temperature of the glass powder is 580-680℃, and / or the average coefficient of thermal expansion of the glass powder at 50-400℃ is 10ppm / ℃-12ppm / ℃. Preferably, the average coefficient of thermal expansion of the glass powder at 50-400℃ is 10.5ppm / ℃-12ppm / ℃; More preferably, the average coefficient of thermal expansion of the glass powder at 50-400°C is 11ppm / °C-12ppm / °C.

6. A media slurry, comprising, by weight 100%, the media slurry as follows: The glass powder comprises 55-80%, cobalt blue 0-5%, organic carrier 8-35%, diluent 3-15%, inorganic additive 0.5-3%, and auxiliary agent 0.2-1% as described in any one of claims 1-5.

7. The media slurry according to claim 6, wherein, The organic carrier includes a resin and a solvent; Preferably, the resin comprises one or a combination of two or more of ethyl cellulose resin, cellulose acetate butyrate resin, and acrylic resin; Preferably, the solvent includes one or a combination of two or more of butyl carbitol acetate, terpineol, DBE, and butyl carbitol.

8. The media slurry according to claim 7, wherein, The weight ratio of the resin to the solvent is (13-35):(65-81). Preferably, the weight ratio of the ethyl cellulose resin, cellulose acetate butyrate resin, acrylic resin and solvent is (8-20):(3-8):(2-7):(65-81).

9. The medium slurry according to claim 6, wherein, The diluent includes one or more of terpineol, butylcarbidol, benzyl alcohol, and dimethyl adipate.

10. The media slurry according to claim 6, wherein, The inorganic additives include one or more of titanium dioxide, copper oxide, nickel oxide, zirconium oxide, and lanthanum oxide.

11. The media slurry according to claim 6, wherein, The additives include thixotropic agents and dispersants; Preferably, the thixotropic agent includes one or more of Thixatrol MAX, CRAYVALLAC MT, and organobentonite, and the dispersant includes one or more of SC-1015F, 211P, and AFB-1521.

12. A thick-film heating element, wherein the raw material comprises the dielectric slurry as described in any one of claims 6-11; Preferably, the substrate of the thick film heating element is made of SUS630 stainless steel, and the surface of the substrate has a dielectric layer, which is formed by sintering the dielectric slurry.

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