TW565691B - Semiconductor type gas sensor and gas sensing device - Google Patents

Abstract

A semiconductor type gas sensor and a gas sensing device using the gas sensor. Co3O4, optionally Au added, is used as sensing material. The concentration of carbon monoxide or hydrogen can be detected by the difference of electric resistance of the sensing material due to the existence of CO or H2. The sensor and the device can be operated at a temperature of T=40 DEG C or above, preferably in a moderate temperature range between 80 and 120 DEG C, for monitoring CO and H2.

Description

565691 _ Case No. 91137648_ Year Month Date__ V. Description of the Invention (1) Field of the Invention The present invention relates to a semiconductor-type gas sensing element, and more particularly to a method using cobalt oxide and selective addition of gold as a sensing element. Semiconductor gas sensing element of material. The present invention also relates to a gas sensing device including the above-mentioned gas sensing element. Previous technologies In air pollution, the sources of carbon monoxide are vehicle exhaust emissions and factory flue emissions. There is also a danger of carbon monoxide leaking when coal or gas is used in homes or factories. China's air quality standard is that the average carbon dioxide concentration per 8 hours should be less than 9 ppm. When the carbon monoxide concentration value reaches 35 p p m in 8 hours, human heart muscle metabolism will be impaired, and vision, hand dexterity, and learning ability will be reduced. When 50 p p m is reached, the human body has headaches and poor hand coordination, and in more severe cases, it will collapse, vertigo, or even comatose and die. Because carbon monoxide gas is colorless, odorless, and non-irritating, it cannot be sensed by the human body, so it cannot be detected unless there are signs of acute poisoning in the presence of large amounts of carbon monoxide. If you can install a carbon monoxide alarm in your home, car, or plant, you can avoid the tragedy of carbon monoxide poisoning. So well-developed carbon monoxide sensors are very important. The conventional gas sensors can be roughly divided into four types: infrared, semiconductor, electrochemical and solid electrolyte. At present, the principles of commercially available sensors for measuring carbon monoxide (C0) concentration include non-dispersive infrared light method, electrochemical method, and semiconductor sensor method. Non-dispersive infrared light sensors are easy to operate, but they are not suitable for analyzing small flow objects and they are expensive. The electrochemical method has the advantage of high sensitivity, but

565691 Fifth price is easy to understand, description of invention (2) ___ convenient and = year limit. Semiconductor type, price quality type, the price will be low: In addition, the solid-state electric beans that have not yet been commercialized are "more convenient and convenient, but the operating temperature is slightly higher. The basic composition of gas sensor gas sensors is semiconductor type for chemical reaction. Library, ί μ J: 4 The gas is adsorbed on the surface of the sensing material and the electrode will follow ;;;: the resistance change of the sensing material is then 'f' in the crystal of the measured material, where n: type + conductor metal oxygen The amount of bonded free electricity i 1: 3, so that there are no body molecules or primitives in the lattice structure; void ⑷ectron h01e). When the gas oxidation or reduction reaction or belongs to the surface of lice compounds, because the degree of occurrence increases or decreases In order to make the electron cavity dense and accessible due to the two thousand absorbed electrons, the gas second resistance changes. 11 By the change of the resistance, the gas will be carbonized, sintered, hydrogen, etc., in the reducing oxide, = 0 ions react on the surface of the object and the electrons are fed back to the resistance to decrease. =: = The hole density will increase and the conductivity will increase, so when the chemical gas is generated; L2 and attached are ozone, oxygen ... Fewer and conductive households; electricity is captured in milk. The electron hole density is reduced by one yak under X, which results in an increase in resistance. 〇4 wt〇j00 In 00, Yamazoe et al. Added 250 ° C in indium oxide (In203), 15 Wt% C. Make a C0 sensor, the best detection temperature is too low (R Air / RJ is 1 65, although the sensitivity is good, but the detection consumption: = 2〇 ^ years, Tsai et al. Used micro-electromechanical (MEMS) Technology to produce ... C (5 ~ 10 mW), small size and no sense of heating

565691 _Case No. 91137648_Year Month Day__ V. Description of the invention (3) Although the detection temperature is only 65 ° C, it has low sensitivity (R Air / R c is about 1 · 9) and selectivity Will be affected by the interference of ethanol and hydrogen. The metal oxide used was tin oxide (Sn02), and palladium (Pd) was further added as a catalyst. In 2002 AD, Li et al. Prepared solid particles (3 ~ 15 nm) of tin oxide (SnO 2) using a solid-state reaction method, and used a traditional screen printing method to detect C0. It has a detection temperature of 1 2 5 ° C and a sensitivity of 3 8. The disadvantage is poor selectivity. The semiconductor type C0 gas sensor literature is summarized in the following Table 1. Table 1 Halide detection temperature CO concentration (PPm) Sensitivity (RAir / Rc〇) Disadvantage C 0-ΙΠ 2 〇3 250 ° C 1000 165 High operating temperature P d- Sn〇2 65 ° C 1000 1.9 Low sensitivity and poor selectivity Sn〇2 125 ° C 100 38 Poor selectivity It is found from the literature that the semiconductor CO sensor has either high detection temperature, low sensitivity, or low selectivity. Good disadvantages. SUMMARY OF THE INVENTION In view of the shortcomings of the foregoing prior art, the object of the present invention is to provide a semiconductor-type gas sensing element and sensing device that can measure carbon monoxide and nitrogen, and has a low detection temperature (above 40 ° C can work, 80 to 1 2 0 ° C is the best detection temperature range) and good selectivity, the sensitivity can also meet the requirements

Page 8 565691 _ Case No. 91137648_ Year Month Amendment _ V. Description of Invention (4). In order to achieve the above-mentioned object of the present invention, the semiconductor-type gas sensing element of the present invention includes: a substrate, a surface of which is provided with a cobalt oxide layer as a sensing material; and two electrodes, each end of which is in contact with the sensing material . Another object of the present invention is to provide a solid-electrolyte-type gas sensing device, including: a gas sensing element, which includes a substrate carrying a cobalt oxide layer on the surface as a sensing material; and two ends each with the sensing Material-connected electrodes; and an electrical connection device connected to the two electrodes. '' The semiconductor-type gas sensing element and sensing device of the present invention can be applied to prevention of danger, detection of toxic gases, environmental protection, home alarm, food quality control, and physical property inspection. The invention has the following advantages: low detection temperature, sufficient sensitivity, and good selectivity. Embodiments The present invention will be described in detail with reference to Fig. 1. The semiconductor-type gas sensing element of the present invention includes: a substrate (1 0), and a cobalt oxide layer on a surface thereof as a sensing material (2 0). The material of the substrate is an inert material that does not participate in the reaction, preferably one with good thermal conductivity, and suitable materials such as alumina and silicon dioxide. The sensing material on the surface of the substrate is screen printed on the surface of the substrate by mixing cobalt oxide (Co 30 4), selective addition of gold, and an appropriate amount of an adhesive, preferably at a temperature of 400 to 600 ° C. It is sintered by heating and removing the organic solvent in the adhesive at about 450 ° C. The oxidized oxide is powdered. When using oxidation and gold, the amount of gold is recorded by oxidation

Page 9 565691 Amendment No. 91137648 V. Description of the invention (5) The total amount of gold is 0. 1 ~ 5%, preferably 0. 5 ~ 3%. The particle diameter of gold is preferably 50 nm or less, more preferably 100 nm or less, and most preferably 5 n rainbow. Adhesive agent can be polyoxyethylene, polyvinyl alcohol or TEE tetraethyl 0rth silicate solution often used in the industry. The proportion of f 接 and cobalt oxide (or cobalt oxide and gold) used depends on The type of the adhesive is generally the right amount of 111, which makes the powders stick together and make the powder form a paste. The solution can be made of Sl (〇c ^) 4 in an appropriate ratio, and can be combined with water and alcohol ^ (for example C2H5〇H, c3H7〇H). Mo one or two electrodes (30) 'each end is connected to the sensing material (20). The electrodes can be reactive and inert materials, with good electrical conductivity For example, ^ m. Each end of the two electrodes is connected to the sensing material layer. See FIG. 3 'The semiconductor-type gas sensing device of the present invention is far from the body sensing element, and includes: (60, connecting device Connect the two electrodes. For example, use two lead values. Tick: The two electrodes are electrically connected to the voltmeter (70) to read the voltage-change material. , t = The measurement circuit of the body gas sensing device can be, for example, a biochemical change. Guide 2 = The sensing used Due to the difference in voltage (v) generated by the adsorption of the gas to be measured, the material can lose 2 resistances. After reading the formula 2W2 at both ends of the reference resistance (R r), the change in the layer resistance (Rs), ... 4. Βί / ^ The watt sensitivity S. S is set to be compared in the air, and you can know the calibration curve ratio made by using the standard concentration for measuring if.

565691 __Case No. 91137648_Year_Month_Fifth, the description of the invention (6)

Rs

P.11 565691 Case No. 91137648_Year_Month_V. Explanation of the invention (7) T Vm Rs + Rf Rf (2-3) Rs:] Rrx- vs-vm Vm, (2-4) V -νΑ. = Rrx 5 VAk (2-5) RGiS =: Rr; n vGas (2-6) ς one RAtr one m) R Gas Va, (Vs-VgJ (2-7) K Gas * Measured in the gas to be measured RSR Air · Rs measured in the air The semiconductor-type gas sensing device of the present invention may further include a heating element for heating the sensing material to facilitate the operation of the gas sensing of the present invention. It is a customary method as long as the material does not interfere with the measurement. For example, referring to FIG. 2, a conventional embodiment of the present invention uses rhodium oxide (40) and two electrodes (50) to connect a power supply ( 80) for heating. It may also include a detection chamber (90) for detecting the gas concentration of the gas to be measured. And it may also have one or more standard gas sources (100), which provide a gas with a known concentration as the detection standard. For already One concentration of carbon oxide or tritium is in air or nitrogen or inactive gas or inert gas. The following preparation examples and examples describe the preparation method of the gas sensing element and the gas sensing device of the present invention in detail. Category doesn't matter

Page 12 565691 __Case No. 91137648_ Year Month Day Amend __ V. Description of the invention (8) Limited to the content of the embodiment. EXAMPLES Preparation Example 1: Preparation of Co3〇4 ^ 10 g of cobalt carbonate basic salt (2CoC03 · 3C〇 (OH) 2 · H20) was heated to 40 ° C for 30 minutes under air to obtain 8 g of C 30 powder. Preparation Example 2: Preparation of Au / Co304. First, 10 g of cobalt carbonate basic salt was heated in the air for 30 minutes to obtain 8 g of Co 3O powder. Then 500 ml of deionized water was taken, 5 g of Co 30 powder was dispersed and suspended therein, and heated to 70 ° C. One gram of HAuCl 4 (HAuCl 4 · 3 Η 20, sold by Aldrich, containing 10 wt% of Au) was diluted with 20 ml of deionized water. The H A u C 1 release solution was dropped into the suspension of the c 〇3 support, and the pH of the solution was controlled at pH = 7 with NaOU Merck Co., Ltd., and stirring was continued for 3 hours. After suspending the suspension, it was washed with deionized water, and the product was dried in an oven. The obtained dried product was reduced in H2O (10% HN2 'Qialong Co., Ltd.) at 20 ° C to obtain Au / C0304, wherein the weight of Au was 1% of C0304. 52%, average particle size is about 3 nm ° Preparation Example 3 · Preparation of Co 30 sensing material Take an appropriate amount of glycerin and drop it into three rollers to roll and lubricate its surface. 5 g of Co3O powder 'was poured into a three-roller and stirred. Then, 0.5 ml of a tetraethyl ortho acid solution (Si (OC2H5) 4: H20: c2H50H = 65 g: 8.27 g) was dropped into the two rollers and stirred for 30 m i η. Made of paste-like sensing material, which is used for screen printing on the substrate surface. Preparation Example 4: Preparation of Au / C 〇30 The sensing material was performed in the same manner as in Preparation Example 3 above, but as in Preparation Example 2

565691 Amendment _ Case No. 91137648 V. Description of Invention (9)

Au / Co 30 4 replaces co 30 4 to produce strong 4, 3, u, used on the surface. 'Money sensing ㈣' for screen printing on the substrate Example 1 Manufacturing of a sensing material COM gas sensing element Once a fnmx 2.5 mm aluminized aluminum substrate was placed two gold electrodes as m 淠 electric wizard, using The screen printing machine sold by CW Price Company screen-printed a layer of the c030 sensing material prepared in Preparation Example 3 between the two measuring gold electrodes, and heated to about 45 CTC to remove the organic solvent, as shown in Figure i. As shown, the gas sensing element of the present invention is completed. In Example 2, the sensing material Au / C03 was used to manufacture a gas sensing element. The gas sensing element was manufactured in the same manner as in Example 1, but Au / Co30 obtained in Preparation Example 4 was used instead of Co3O4. Example 3 Manufacture of a gas sensing device On the other side of the substrate of the sensing element obtained in Example 1, a heating element is disposed on the other side of the substrate, including an oxide layer and Erto mrf „innn 士 立 丨 儿 极 ' The screen printing method is used to paste an oxidation paste (about 100 Ω), sintered at a high temperature of 40 Ω, and use a wiring machine to heat the rhodium ions into α ^ r L t. Put a platinum wire. Connect the sensing element to the measurement base. # Ji θ ^ Place the obtained gas sensing element together with the base in a room. Connect the wire to the battery with a wire connected to the thermal element. Coin, measuring Λ To · By adding, connecting, and heading 丨 丨 —Tian Leiyang charges a few feet, connects an voltmeter with an electrode, and measures the potential carbon generated by the double resistance. The carbon is connected to the air cylinder with a tube. It has been mixed from your liver to I before it enters the testing room. J is: 1) Carbonized carbon and air are used for the intake. Methane is used instead of carbon monoxide for comparison. 565691 ___Case No. 91137648_ Year and Month Amendment_ 5 2. Description of the invention (10) Embodiment 4 The manufacturing of the gas sensing device is as described in Embodiment 3. The gas sensing device was manufactured in the same steps, but the gas sensing element Au / Co 300 gas sensing element of Example 2 was used instead of the gas sensing element of Example 1. The following description uses the gas sensing element of the present invention. The result of testing the sample by the measuring device. In order not to pass C 0, Η and C 1 of 1000 pp claws at a flow rate of 100 m 1 / mi η for gas sensing. Use C 0 30 as the sensor Measure the sensitivity of the material at various temperatures (S) vs. temperature to obtain Figure 4. The sensitivity s is defined as described above. It shows that the detection of CH gas is not sensitive, but for co and radon gas, it is about 4 (The signal can be obtained after TC. For C0, the best signal can be obtained at about 80.0%,% Mai read Figure 6 'You can get the signal at about 40 ° C, please refer to Figure 7. ^ Use Au / C〇30 is a sensing material, the sensitivity obtained at various temperatures, (S) is plotted against the temperature to obtain Figure 5. It shows that the detection of CH is not sensitive, but for CO and hydrogen, The signal is obtained at about 4 ot: For C0, the best signal is obtained at about 8 (rc, see section 8 The signal can be obtained at about 40 ° C, please refer to Fig. 9. It is also found that in the temperature range of 70 to wot, the sensing material with Au / Co 30 # is more sensitive than C 0 30 The test material has better selectivity to carbon monoxide. = List 2 shows the scs of the present invention using c030 and Au / c030 test materials, test results. The initial detection temperature (τ. 〇t :, the reaction time 190) is about 20 to 30 seconds, and the optimal detection temperature can be between 8.0 and 1.00, which is much lower than the conventional technique.

565691 _Case No. 91137648_ Year, month, day, date, five, description of the invention (11) ts / ° C but 0 / eC STo t90 / second CO3O4 CO 40 80 3.8 20 h2 40 100 3 90 ch4 70 90 1.3 25 AU / CO3O4 CO 40 100 3.7 30 H2 40 80 1.9 90 ch4 70 100 1.1 20

Ts: the lowest estimated temperature T. : Best guess temperature sT. : Highest sensitivity t90: Response time Although the present invention has been disclosed in the preferred embodiment as above, it is not intended to limit the present invention. Anyone skilled in the art can make some changes without departing from the spirit and scope of the present invention. Changes and retouching, so the protection scope of the present invention shall be determined by the scope of the appended patent application.

Page 16 565691 _Case No. 91137648_ Year Month Day__ Brief Description of Drawings Figure 1 shows a schematic diagram of the structure of a gas sensing element according to an embodiment of the present invention. Fig. 2 is a schematic diagram of a heating structure for heating the gas sensing element of the present invention. Fig. 3 is a schematic diagram of a gas sensing device according to an embodiment of the present invention. Fig. 4 is a result of sensing one thousand ppm different gases (hydrogen, carbon monoxide, and pinane) according to an embodiment of the present invention using a Co30 material, and plotting a signal and a sensing temperature. Fig. 5 is a sensing result of 1000 ppm of different gases (hydrogen, carbon monoxide, and sintering) using an embodiment of the Au / Co30 material according to the present invention, and the signal and the sensing temperature are plotted. Fig. 6 is a response curve of an embodiment of the present invention using a Co 30 material at 80 ° C. Fig. 7 is a response curve of an embodiment of the present invention using Co 30 material at 40 ° C. Fig. 8 is a response curve of an embodiment of the present invention using Au / Co30 material at 80 ° C. Figure 9 is the response curve of one embodiment of the present invention using Au / Co30 material at 40 ° C. Explanation of symbols 1 0 ~ substrate; 2 0 ~ sensing material; 3 0 ~ electrode;

Page 17 565691 _ Case No. 91137648_ Year, month, day, correction diagram, simple explanation 40 ~ heating material; 50 ~ electrode (for heating); 60 ~ wire; 6 wire; 70 ~ voltmeter; 80 ~ power 9 0 ~ detection chamber; 100 ~ gas source; 1 (H ~ test gas; 102 ~ air; 1 10 ~ sensing element.

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Claims (1)

565691 —- ~ _11 ^ 91137648_ Year of the month ^ 6. Patent application scope '1 · A semiconductor-type gas sensing element suitable for inspection, or hydrogen, including: Μ carbon monoxide-substrate, the surface of which is loaded with a cobalt oxide layer to do It is a sensing material. Two electrodes, each end of which is in contact with the sensing material. / ', And 2 · The semiconductor gas device as described in item 丨 of the patent application range, wherein the sensing material further comprises the total weight of the sensing material; Ye 0.5 · 3 Special 3 · The semiconductor-type gas piece as described in the first item of the patent application scope, wherein the sensing material is made of cobalt oxide powder and an appropriate amount followed by a sensing element, and the screen is sintered on the surface of the substrate. Made. ^ Here after the 4 · Semiconductor gas parts as described in item 3 of the scope of patent application, wherein the sintering temperature is between 400 and 60 0 t. Iron residue 5. The semiconductor gas as described in item 3 of the scope of the patent application, wherein the adhesive is selected from the group consisting of polyoxy-ethyl / thenyl vinyl alcohol, tetraethyl orthosilicate Esters (TEOs), and mixtures thereof. Ethylene, Poly 6. The semiconductor gas device as described in item 5 of the scope of the patent application, wherein the adhesive is tetraethyl orthosilicate. ~ 3 yuan 7 · The semiconductor gas device as described in item 1 of the scope of patent application, wherein the material of the substrate is alumina or silicon dioxide. ▼ ^ Ji 8 · —Semiconductor-type gas sensing device, suitable for detecting one or hydrogen, including ·· Li etiquette carbon-gas sensing element, including a substrate carrying a cobalt oxide layer on the surface as a material and two substrates each An electrode connected at one end to the sensing material; 1 measures an electrical connection device and connects the two electrodes. ’ 565691 __ 索 号 91137648 ___ ± _J-^ __ Amendment_ VI. Patent application scope 9 · The semiconductor-type gas sensing device described in item 8 of the patent application scope, wherein the sensing material further includes a total of sensing material 0.5 to 3 weight 0 / ◦ gold. 10 · The semiconductor-type gas sensing device as described in item 8 of the scope of patent application, wherein the sensing material is sintered by screen printing on the surface of the substrate after mixing cobalt oxide powder and an appropriate amount of an adhesive. 1 1 · The semiconductor-type gas sensing device described in item 10 of the scope of the patent application, wherein the sintering temperature is between 400 and 600 ° C. 1 2 · The semiconductor-type gas sensing device as described in item 10 of the scope of patent application, wherein the adhesive is selected from the group consisting of polyoxyethylene, polyvinyl alcohol, tetraethyl orthosilicate (TEOS ), And mixtures thereof. 1 3. The semiconductor-type gas sensing device according to item 12 of the scope of the patent application, wherein the adhesive is tetraethyl orthosilicate. 1 4 · The semiconductor-type gas sensing device described in item 8 of the scope of patent application, further comprising a heating element for heating the sensing material. 1 5 · The semiconductor-type gas sensing device described in item 14 of the scope of patent application, wherein the heating element is placed on the other surface of the substrate and is composed of two electrodes and a rhodium oxide layer. 16 · The semiconductor-type gas sensing device as described in item 8 of the scope of patent application, wherein the material of the substrate is alumina or silicon dioxide. Page 20