A metal oxide semiconductor far-infrared heating microcrystalline glass with adjustable power and temperature and its preparation method.

Abstract

This invention discloses a metal oxide semiconductor far-infrared heating microcrystalline glass with adjustable power and temperature, and its preparation method. The product consists of a multilayer functional structure equipped with silver paste guiding electrodes. Its substrate is a Li2O–Al2O3–SiO2-based microcrystalline glass with a pore size of 50~100nm; each functional layer has a specific doping ratio, sheet resistance, and conductivity parameters. The product is manufactured through pretreatment, magnetron sputtering, sintering, gradient annealing, and protective layer curing. Its operating temperature can be adjusted from 80~350℃ by adjusting the doping ratio, film thickness, and DC24~AC220V voltage. Its far-infrared emission band is 4~20μm, its normal emissivity is ≥0.85, and its electrothermal efficiency is more than 15% higher than that of traditional ITO heating glass. It can be widely used in household heating, baking, and industrial drying heating applications.

Description

Technical Field

[0001] This invention belongs to the technical fields of far-infrared electrothermal functional materials, heating elements for household appliances, and industrial high-temperature drying and heating appliances. Specifically, it relates to a far-infrared heating microcrystalline glass with microcrystalline glass as the substrate, a multilayer gradient composite metal oxide semiconductor thin film, and continuously adjustable voltage and temperature control, as well as its industrial preparation process. Background Technology

[0002] Most existing electrothermal heating substrates use mica, ordinary soda-lime glass, or alumina ceramic to support ITO conductive films or thick-film resistive pastes, which have several key defects:

[0003] (1) Poor temperature resistance: Conventional glass has a softening point below 550℃ and is prone to softening and deformation and thermal performance degradation under long-term high-temperature conditions of 300~600℃.

[0004] (2) Easy to peel off between layers: The thermal expansion coefficients of the traditional organic resin protective layer, low-temperature ordinary glaze and substrate and heating film are not matched, and blistering, peeling and falling off occur in rapid cooling and heating environments;

[0005] (3) Uncontrollable electrothermal parameters: The sheet resistance of printed resistive paste has a large dispersion, which cannot accurately match the requirements of low-voltage start-up and high-power output. The far-infrared emission band is narrow and the radiation heat exchange efficiency is low.

[0006] (4) Potential problems with aging of the protective layer: The organic binder does not completely volatilize when heated, leaving micropores inside the membrane. Long-term energization and water vapor intrusion can cause resistance drift and device failure.

[0007] (5) High energy consumption and low fault tolerance: There is no heat insulation base and backup conductive structure, a large amount of heat is lost to the back of the substrate and the thermal response is slow; if a single point of the heating layer is damaged, the whole piece will be broken and scrapped, resulting in a short product life.

[0008] Based on existing research and development achievements in semiconductor heating films, traditional microcrystalline heating glass lacks a fully closed-cell thermal insulation substrate, gradient transition layer, discrete support and isolation structure, and rare earth composite shielding layer. Therefore, this invention optimizes and improves the substrate formulation, multilayer film structure, and doping system. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing heating glass, such as insufficient high temperature resistance, poor interlayer bonding, inability to linearly adjust power and temperature, low far-infrared efficiency, easy aging and detachment, high energy consumption, and overall scrapping due to single-point damage. The invention provides an adjustable power far-infrared heating microcrystalline glass with an all-inorganic multilayer composite structure, controllable oxygen vacancies, heat insulation and shielding protection, and backup conductive path, as well as its preparation method.

[0010] (a) Overall product structure (layered from bottom to top, corresponding to Figure 1)

[0011] The heating microcrystalline glass of the present invention comprises, from bottom to top, a microcrystalline glass substrate, a gallium boron cerium doped zinc oxide transition layer, a SiO2 insulating support layer with arrayed through holes, a zirconium gallium co-doped indium oxide semiconductor heating layer, a rare earth composite zinc oxide shielding layer, and a silicate inorganic protective layer, with silver paste electrodes disposed at the left and right ends of the heating layer.

[0012] Microcrystalline glass substrate: The base is a Li2O–Al2O3–SiO2 microcrystalline glass plate (softening point > 700℃); it can be optimized to a fully closed-cell modified structure with SiO2:Al2O3 = 75~85:15~25, with a closed-cell diameter of 50~100nm, to achieve back heat insulation and loss reduction and block water vapor erosion.

[0013] Transition buffer layer: gallium, boron, and cerium co-doped zinc oxide thin film, supplemented with trace amounts of rare metals such as niobium, tantalum, iridium, and osmium (total doping < 0.15 at%), surface roughness ≤ 5 nm, sheet resistance > 100 Ω / □, low normal current shunt, can serve as a backup conductive layer after the heating layer is damaged.

[0014] Discrete support isolation layer: composed of SiO2 insulating dielectric film and array of through-hole conductive filler; the through-hole opening rate of the heating zone is 3%~8%, and the through-holes are filled with tungsten, tungsten-rhenium, molybdenum or titanium-tungsten alloy, with a filling density >98% and a contact resistance <1×10⁻³Ω·cm²; this layer isolates the heating layer from the entire surface contact of the transition layer, and conducts electricity only vertically at the through-hole points, dispersing thermal stress and preventing interlayer leakage and element interdiffusion.

[0015] Semiconductor heating layer: based on In2O3, composite with ZnO and SnO2 and doped with Zr and Ga; film thickness 0.5~2μm, precise oxygen vacancy ROV=26%~30%, sheet resistance <100Ω / □, far-infrared radiation band 4~20μm.

[0016] Composite shielding and inorganic protective layer: The inner layer is a zinc oxide shielding film co-doped with cerium, boron, gallium, SiO2 and trace rare earth elements; the outer layer is a silicate / phosphate inorganic high-temperature insulating glaze, which is stepped to form a dense inorganic protective layer that has the functions of insulation, corrosion prevention, oxygen barrier and electromagnetic shielding.

[0017] Silver paste electrodes: High-temperature sintered silver conductive electrodes at both ends of the heating layer, connected to an external DC24V~AC220V power supply; the heating power and plate temperature can be linearly changed by continuously adjusting the applied voltage.

[0018] (II) Preparation process (corresponding to Figure 2 process flow)

[0019] 1) Substrate pretreatment: polishing of microcrystalline glass plate surface → plasma cleaning → ultrasonic degreasing → drying at 120℃; if full closed-cell modification is required, then silicon-aluminum powder is mixed → pressed at 20MPa → sintered at 1200℃ for 2h to form a closed-cell substrate.

[0020] 2) Silver electrode pre-preparation: Silver paste is printed on both sides of the substrate and cured in a tunnel oven at 650℃ for 8~12 minutes.

[0021] 3) Transition layer magnetron sputtering: vacuum degree 1×10⁻³~5×10⁻³Pa, substrate temperature 250~350℃, power 80~150W, depositing zinc oxide-based transition thin film.

[0022] 4) Support layer formation: deposit SiO2 insulating film → photolithography etching array vias → vacuum high pressure filling of tungsten rhenium alloy, low temperature densification annealing.

[0023] 5) Preparation of heating layer: Oxide powder is ball-milled to micron level to form a slurry, deposited by high-temperature spraying or magnetron sputtering, sintered at 650℃ for 5~8 min, and the oxygen partial pressure in the chamber is adjusted to lock the ROV to 26~30%.

[0024] 6) Gradient annealing: 650℃ is uniformly reduced to 480℃ at a rate of 3~5℃ / min, and held for 30min to eliminate internal stress and stabilize the lattice and oxygen vacancies.

[0025] 7) Curing of shielding and protective layers: magnetron sputtering of rare earth composite zinc oxide shielding layer, roller coating of silicate inorganic paint; segmented curing: pre-baking at 80℃ for 15min → curing at 300℃ for 20min, and natural cooling of finished product.

[0026] (III) Power Temperature Control Principle

[0027] Back-end electrical control: The external power supply voltage DC24~220V is continuously adjustable to linearly change the heating power and board temperature; Front-end process: The sheet resistance is adjusted by controlling the doping ratio of the heating layer, film thickness, and sputtered oxygen partial pressure to customize products with different constant temperature ranges of 80~350℃.

[0028] Beneficial effects:

[0029] (1) High temperature resistance: The microcrystalline substrate softens to >700℃, the maximum preparation temperature is 650℃, and there is no deformation or thermal decay during long-term continuous operation at 350℃; the fully closed-cell substrate reduces back heat loss by more than 15%, saving energy and reducing consumption.

[0030] (2) Strong bonding: High-temperature sintering and gradient annealing achieve chemical bonding between the film and glass; the discrete support layer disperses the thermal stress of cold and hot cycles, and the inorganic protective layer matches thermal expansion, so that it does not peel off after thousands of cold and hot cycles.

[0031] (3) Parameter controllable: Zr / Ga multi-doping and precise oxygen vacancy control allow for linear adjustment of sheet resistance and output power through multiple methods such as formulation, film thickness and voltage, and stable temperature control of 80~350℃.

[0032] (4) Far-infrared high efficiency: radiation in the 4~20μm biological optimal absorption band, normal emissivity ≥0.85, electrothermal conversion efficiency is more than 15% higher than that of traditional ITO.

[0033] (5) Aging and corrosion resistant: The all-inorganic protective layer has no organic residue and no internal pores; the rare earth composite shielding layer blocks oxygen and prevents bidirectional diffusion of metal ions, stabilizes oxygen vacancies, and has a resistance drift of <±3%; electromagnetic shielding ≥35dB.

[0034] (6) High fault tolerance: The high-resistivity transition layer serves as a backup conductive path. Even if the heating layer is partially damaged, it can still generate heat, thus avoiding the scrapping of the entire piece. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the longitudinal cross-sectional structure of the heating microcrystalline glass of the present invention;

[0036] Figure 2 is a flowchart of the product preparation process of the present invention.

[0037] In the figure: 1—Inorganic shielding and protective layer; 2—Zirconium gallium co-doped indium oxide heating layer; 3—Discrete support layer; 31—Tungsten rhenium alloy conductive filler; 4—Gallium boron cerium doped zinc oxide transition layer; 5—Fully closed-cell modified microcrystalline glass substrate; 6—Side silver paste electrode. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the embodiments of the present invention are not limited thereto. The structure of each layer is shown in Figure 1. From bottom to top, the layers are: microcrystalline glass substrate 5, gallium boron cerium doped zinc oxide transition layer 4, discrete support layer 3 with arrayed through holes 31, zirconium gallium co-doped indium oxide heating layer 2, inorganic shielding and protective layer 1, and silver paste electrodes 6 are provided at the left and right ends of the heating layer 2.

[0039] Example 1 (Substrate silicon-to-aluminum ratio 75:25, closed-cell pore size 50nm, support open-cell ratio 3%)

[0040] S1: A fully closed-cell microcrystalline composite substrate 5 was prepared by sintering SiO2:Al2O3=75:25 at 1200℃, polished and cleaned, and then baked with silver paste at 650℃ for 10 min to form an electrode 6.

[0041] S2: Transition layer 4 is co-doped with zinc oxide containing 1 at% Ga, 0.5 at% B, 0.1 at% Ce, and 0.15 at% niobium, with a sheet resistance of 115 Ω / □; Support layer 3 has an open porosity of 3% and a tungsten-rhenium filling density of 98.2%.

[0042] S3: Heating layer 2, doped with Zr 1.5mol%, Ga 2.0mol%, film thickness 0.5μm, oxygen vacancy ROV=26%;

[0043] S4: Gradient annealing with a cooling rate of 3℃ / min; the shielding layer is made of Ce 0.8at% and scandium 0.05% rare earth; the inorganic paint is cured in stages from 80℃ to 300℃.

[0044] Example 2 (preferred ratio, silicon-aluminum ratio 80:20, pore size 75nm, porosity 5%)

[0045] S1: Closed-cell substrate 5 is made of SiO2:Al2O3=80:20; support layer 3 has an open porosity of 5% and a filler density of 98.5%;

[0046] S2: Heating layer 2 is doped with Zr 2.5 mol%, Ga 3.0 mol%, film thickness 1.2 μm, ROV=28%; Transition layer 4 is doped with Ga 2.5 at%, B 0.8 at%, Ce 0.3 at%; Shielding layer is doped with Ce 1.2 at% and yttrium 0.08% rare earth.

[0047] Example 3 (High-power version, silicon-to-aluminum ratio 85:15, pore size 100nm, porosity 8%)

[0048] S1: A closed-cell substrate 5 is made of SiO2:Al2O3=85:15, and a support layer 3 has an open porosity of 8% and a filling density of 98.8%.

[0049] S2: Heating layer 2 is doped with Zr 3.5 mol%, Ga 4.0 mol%, film thickness 2 μm, ROV=30%; the shielding layer is made of Ce 1.5 at% plus lanthanum and lutetium total rare earth 0.11%.

[0050] Comparative Example 1 (no support layer, heating layer and transition layer are fully bonded, the rest is the same as in Example 2); Comparative Example 2 (using ordinary solid glass substrate without closed pores, the rest is the same as in Example 2); Comparative Example 3 (heating layer oxygen vacancy ROV < 26%, no rare earth shielding layer, the rest is the same as in Example 2).

[0051] The performance data comparison is shown in the table below:

[0052] Example 1 0.86 88.2 ±1.2 36.1 1.1 Example 2 0.88 92.5 ±0.9 38.7 0.8 Example 3 0.87 90.3 ±1.0 40.1 0.9 Comparative Example 1 0.85 83.1 ±3.5 38.3 4.6 Comparative Example 2 0.84 81.3 ±4.2 35.6 5.2 Comparative Example 3 0.82 79.6 ±2.8 14.8 6.8

[0053] Test conditions: Input voltage 24~220V, temperature control range 80~350℃; The sample in the example underwent 1000 cycles of room temperature to 350℃ without cracking or peeling.

[0054] The data in the table shows that, compared to the comparative examples, the embodiments of the present invention are significantly superior in terms of infrared emissivity, electrothermal efficiency, sheet resistance uniformity, electromagnetic shielding, and thermal cycling stability; among them, Example 2 has the best overall performance. Comparative Example 1 suffers from a significant decrease in sheet resistance uniformity and thermal cycling stability due to the lack of a discrete support layer; Comparative Example 2 uses a solid glass substrate, resulting in increased back heat loss and reduced electrothermal efficiency; Comparative Example 3 has low oxygen vacancies and lacks a rare-earth shielding layer, leading to a sharp decrease in electromagnetic shielding and increased resistance drift.

[0055] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A metal oxide semiconductor far-infrared heating microcrystalline glass with adjustable power and temperature, characterized in that: From bottom to top, the structure consists of a microcrystalline glass substrate, a gallium-boron-cerium-doped zinc oxide transition layer, a SiO2 insulating support layer with arrayed through-holes, a zirconium-gallium co-doped indium oxide semiconductor heating layer, a rare-earth composite zinc oxide shielding layer, and a silicate inorganic protective layer. Silver paste electrodes are provided at both ends of the heating layer. The microcrystalline glass can be a SiO2-Al2O3 fully closed-cell modified structure with a silicon-to-aluminum mass ratio of 75-85:15-25 and a closed-cell diameter of 50-100 nm. The through-hole opening rate in the heating zone of the support layer is 3%-8%, and the through-holes are filled with tungsten / tungsten-rhenium / molybdenum alloy conductive filler with a filling density >98% and a contact resistance <1×10⁻³Ω·cm². The heating layer uses In2O3 as the substrate, with Zr doping of 1.5-3.5 mol%, Ga doping of 2.0-4.0 mol%, and oxygen vacancy (ROV) of 26-30%. The sheet resistance of the heating layer is <100 Ω / □, and the sheet resistance of the transition layer is >100 Ω / □. The shielding layer is made of Ce... It is composed of zinc oxide co-doped with rare earth elements, including 0.8~1.5at%, B 0.5~1.2at%, Ga 0.5~1at%, SiO2 0.3~0.8at%, and total molar percentage <0.12%.

2. The heating microcrystalline glass according to claim 1, characterized in that: The transition layer raw material ratio is Ga 1~4at%, B 0.5~1.2at%, Ce 0.1~0.5at%, and the total doping of rare metals such as niobium, tantalum, iridium and osmium is <0.15at.

3. The heating microcrystalline glass according to claim 1, characterized in that: The heating layer substrate has a mass ratio of In2O3 82~88%, ZnO 9~14%, SnO2 2~4%, and a film thickness of 0.5~2μm.

4. A method for preparing the heating microcrystalline glass according to any one of claims 1 to 3, characterized in that: The process includes seven major steps: substrate pretreatment, silver electrode pre-firing at 650℃, transition layer magnetron sputtering, support layer photolithography and metal filling, heating layer high-temperature sintering at 650℃, gradient annealing from 650℃ to 480℃, shielding layer coating and inorganic paint pre-baking at 80℃ / curing at 300℃; among which, the magnetron sputtering vacuum degree is 1×10⁻³~5×10⁻³Pa, sputtering temperature is 250~350℃, and power is 80~150W.

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