Rare earth oxide doped cerium oxide-based ceramic powder, preparation method and application thereof, and solid oxide fuel cell

Abstract

The present invention belongs to the field of solid oxide fuel cells, and specifically relates to a rare earth oxide doped cerium oxide-based ceramic powder, a preparation method and application thereof, and a solid oxide fuel cell. The method comprises the following steps: S1, dissolving a cerium source and a rare earth source in an organic solvent, stirring evenly to obtain a mixed solution; S2, adding a complexing agent to the mixed solution and mixing evenly to obtain a mixed system; S3, adding an organic precipitant to the mixed system, and obtaining a precursor after standing at a constant temperature; S4, annealing the precursor to obtain a rare earth oxide doped cerium oxide-based ceramic powder. The beneficial effects of the present invention are: 1. The fluidity (angle of repose less than 50°) of the rare earth oxide doped cerium oxide-based ceramic powder prepared by the method of the present invention is better than that of the powder prepared by the water system co-precipitation method (angle of repose 54°) and the glycine combustion method (angle of repose 70°) of the same component, and is more conducive to the application in electrolytes.

Description

Technical Field

[0001] The present invention belongs to the field of solid oxide fuel cells, and in particular relates to a rare earth oxide-doped cerium oxide-based ceramic powder, a preparation method and application thereof, and a solid oxide fuel cell. Background Art

[0002] Energy is the foundation of human social development and the driving force of the industrial revolution. Clean and efficient energy technology has always been the pursuit of social development and environmental protection. Although fuel cells are called batteries, they are essentially different from traditional dry batteries or secondary batteries. They are a technology that directly converts the chemical energy of fuel into electrical energy through electrochemical methods. They do not require a combustion process and are not restricted by the thermodynamic Carnot cycle. They have a high energy conversion rate and the products are clean and pollution-free. Therefore, they have received attention from many aspects.

[0003] The fuel cell is mainly composed of three parts: cathode, electrolyte and anode. The electrolyte plays a role in transporting O 2- The widely used electrolytes are zirconia-based, cerium-based and LSGM materials. Pure cerium oxide materials cannot be used directly as electrolyte materials due to their low ionic conductivity. Their ionic conductivity can be improved by doping with low-valent oxides, such as samarium oxide, gadolinium oxide, yttrium oxide and other rare earth oxides or divalent alkaline earth metal ions Ca 2+ When substituted, oxygen vacancies are generated in the lattice, and the oxygen ion conductivity of the material is greatly improved. Among them, the factors that affect the performance of the electrolyte include particle size, morphology, initial structure, etc. in addition to the components, and the preparation method directly affects the particle size, uniformity, morphology, specific surface area, sintering activity and uniformity of doping of the powder. There are many methods for preparing doped cerium oxide ceramic powders, such as solid phase reaction, sol-gel method, coprecipitation method, combustion method, etc. These methods have their own advantages and disadvantages, but high ionic conductivity is a consistent pursuit. In addition, in practical applications, the electrolyte layer is generally prepared by screen printing, casting or dry pressing; in the screen printing or casting process, the doped cerium oxide powder needs to be mixed with a solvent to form a slurry. The low fluidity of the powder will lead to too high viscosity of the slurry and reduced solid content, which is not conducive to screen printing or casting; in the dry pressing method, the low fluidity of the doped cerium oxide powder will lead to a decrease in the flatness of the green body, uneven stacking, and the doped cerium oxide powder will remain on the surface of the mold.

[0004] The solid phase reaction method is simple in process, does not require the use of solvents, has high raw material selectivity and high yield, and is easy to achieve large-scale production. However, the powder prepared by this method has large particle size, uneven particles, high sintering temperature, and low conductivity of the electrolyte due to the grain boundary effect of large grains. The Gd prepared by the solid phase method reported by Balazs et al. 0.2 Ce 0.8 O 1.9The electrical conductivity is about 0.009 S / cm at 600°C (Balazs GB, Glass R S. AC-impedance studies of rare-earth-oxidedoped ceria. Solid State Ionics[J]. 1995, 76: 155-162.).

[0005] Compared with the solid phase method, the electrolyte powder particles prepared by the sol-gel method are more uniform, and theoretically should obtain higher conductivity. However, Pinol et al. (Pinol S, Najib M, Bastidas DM, et al. Microstructure-conductivity relationship in Gd-and Sm-doped ceria-based electrolytes prepared by the acrylamide sol-gel-related method. Journal of Solid State Electrochemistry [J]. 2004, 8: 650-654.) reported that the Gd 0.2 Ce 0.8 O 1.9 The conductivity is about 0.0114S / cm at 600°C, which is higher than the solid phase method but has no obvious advantages. In addition, the sol-gel method is costly and has a strict process, making its industrial production difficult.

[0006] The co-precipitation method is to use an excess of precipitants (such as ammonium carbonate, urea, ammonium oxalate, ammonia water, etc.) to precipitate metal nitrates or chlorides in the water system at the same time. The intermediate products obtained are usually hydrated oxides, carbonates or oxalate precipitates. The type, concentration, pH, reaction temperature, dropwise addition method, and standing time of the precipitant in the reaction will have a great influence on the morphology and physicochemical properties of the product. The electrolyte particles prepared by this method have the characteristics of small particles, high activity, good uniformity, low phase formation temperature, and good sintering activity. The Gd obtained by Zha et al. 0.2 Ce 0.8 O 1.9 、Sm 0.2 Ce 0.8 O 1.9 The conductivity of the powders at 600°C is 0.0155S / cm and 0.0212S / cm respectively. The performance is significantly improved compared with the solid phase method and sol-gel method, and the cost is low, and the difficulty of industrial production is low; however, the initial particle size of the powder prepared by the water system co-precipitation method is small, the primary particles are easy to agglomerate, and the fluidity is poor.

[0007] The powder produced by the glycine-nitrate co-combustion method has the characteristics of small particles, high activity, and low bulk density. Peng et al. (Peng R, Xia C, Fu Q, et al. Sintering and electrical properties of (CeO2) 0.8 (Sm2O3) 0.1 Sm obtained from powders prepared by glycine-nitrate process.Materials Letters[J].2002,56:1043-1047.) 0.2 Ce 0.8 O 1.9 The electrical conductivity of the powder at 600°C is 0.016S / cm, which is similar to the co-precipitation result. However, since a large amount of heat is released during the spontaneous combustion process and the product is ejected with the flame, the yield of this method is low and the powder preparation process conditions are harsh, making it unsuitable for expanding production. In addition, the obtained powder has uneven particle size, irregular morphology, and poor fluidity. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a rare earth oxide-doped cerium oxide-based ceramic powder, a preparation method and application thereof, and a solid oxide fuel cell. The electrolyte ceramic prepared using the ceramic powder has higher ionic conductivity. The cerium oxide-based ceramic powder prepared by this method has higher ionic conductivity, and at the same time overcomes the problems of easy agglomeration and poor fluidity of the powder in the prior art, and has good application prospects in the field of solid oxide fuel cells.

[0009] In order to overcome the above problems, one of the objects of the present invention is to provide a method for preparing a rare earth oxide-doped cerium oxide-based ceramic powder, comprising the following steps:

[0010] S1, dissolving a cerium source and a rare earth source in an organic solvent, and stirring to obtain a mixed solution;

[0011] S2, adding a complexing agent to the mixed solution and mixing evenly to obtain a mixed system;

[0012] S3, adding an organic precipitant to the mixed system, and keeping it at a constant temperature to obtain a precursor;

[0013] S4, annealing the precursor to obtain a rare earth oxide-doped cerium oxide-based ceramic powder;

[0014] The rare earth source is selected from at least one of a lanthanum source, a praseodymium source, a neodymium source, a promethium source, a samarium source, a europium source, a gadolinium source, a terbium source, a dysprosium source, a holmium source, an erbium source, a thulium source, a ytterbium source, a lutetium source, a scandium source and a yttrium source.

[0015] The second object of the present invention is to provide a rare earth oxide-doped cerium oxide-based ceramic powder prepared according to the above method.

[0016] The third object of the present invention is to provide the use of the rare earth oxide-doped cerium oxide-based ceramic powder in solid oxide fuel cell electrolytes.

[0017] A fourth object of the present invention is to provide a solid oxide fuel cell comprising the aforementioned electrolyte.

[0018] The beneficial effects of the present invention are:

[0019] 1. The fluidity (angle of repose less than 50°) of the rare earth oxide-doped cerium oxide-based ceramic powder prepared by the method of the present invention is better than that of the powders prepared by the water system co-precipitation method (angle of repose 54°) and the glycine combustion method (angle of repose 70°) of the same components, and is more conducive to the application in electrolytes;

[0020] 2. The electrolyte ceramics prepared using this ceramic powder have higher ionic conductivity (0.050S / cm at 750°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a SEM image of the rare earth oxide-doped cerium oxide-based ceramic powder prepared in Example 1;

[0022] Figure 2 is a SEM image of the rare earth oxide-doped cerium oxide-based ceramic powder prepared in Comparative Example 1;

[0023] Figure 3 This is a SEM image of the rare earth oxide-doped cerium oxide-based ceramic powder prepared in Comparative Example 2. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] In the following content, the rare earth elements mentioned are all rare earth elements other than cerium; the rare earth ions are all rare earth ions other than cerium ions.

[0026] “Rare earth oxide doped cerium oxide-based ceramic powder” is hereinafter referred to as “doped CeO2 powder”.

[0027] As mentioned above, the present invention provides a method for preparing rare earth oxide-doped cerium oxide-based ceramic powder, comprising the following steps:

[0028] S1, dissolving a cerium source and a rare earth source in an organic solvent, and stirring to obtain a mixed solution;

[0029] S2, adding a complexing agent to the mixed solution and mixing evenly to obtain a mixed system;

[0030] S3, adding an organic precipitant to the mixed system, and keeping it at a constant temperature to obtain a precursor;

[0031] S4, annealing the precursor to obtain a rare earth oxide-doped cerium oxide-based ceramic powder;

[0032] The rare earth source is selected from at least one of a lanthanum source, a praseodymium source, a neodymium source, a promethium source, a samarium source, a europium source, a gadolinium source, a terbium source, a dysprosium source, a holmium source, an erbium source, a thulium source, a ytterbium source, a lutetium source, a scandium source and a yttrium source.

[0033] In the present invention, by using an organic precipitant in an organic solvent to carry out a coprecipitation reaction on rare earth metal ions and cerium ions, the obtained doped cerium oxide powder has higher conductivity and fluidity and is more conducive to application in electrolytes.

[0034] According to the present invention, under preferred conditions, in S1, the cerium source is selected from inorganic cerium salts, and the types of the inorganic cerium salts include but are not limited to at least one of cerium nitrate hexahydrate, cerium chloride heptahydrate, ammonium cerium nitrate, cerium sulfate, ammonium cerium sulfate and cerium acetate, preferably cerium chloride heptahydrate.

[0035] According to the present invention, under preferred conditions, the rare earth source is preferably selected from at least one of yttrium source, lanthanum source, praseodymium source, neodymium source, promethium source, samarium source, europium source, gadolinium source, terbium source, dysprosium source and ytterbium source; further preferably, the rare earth source is selected from at least one of rare earth metal nitrates, rare earth metal chlorides, rare earth metal sulfates and rare earth metal acetates; more preferably, the rare earth source is selected from rare earth metal chlorides.

[0036] Preferably, the organic solvent is selected from at least one of methanol, ethanol, propanol, ethylene glycol, dimethyl sulfoxide, dimethylformamide acetone, acetone, cyclohexanone and 2-butanone.

[0037] According to the present invention, under preferred conditions, in S1, the rare earth ion concentration accounts for 3%-20% of the total metal ion concentration, and the total metal ion concentration is the sum of the rare earth ion concentration and the cerium ion concentration, and the concentration refers to the molar concentration.

[0038] In the present invention, compared with rare earth metal ions, the reaction between the cerium source containing crystal water and the organic precipitant is more intense. In addition, in the mixed solution in step S1, the concentration of cerium ions is much greater than that of rare earth metal ions, resulting in a precipitation rate of cerium ions greater than that of rare earth metal ions, thereby resulting in uneven distribution of rare earth metal oxides in the product. According to the present invention, under preferred conditions, in order to suppress the reaction rate, a complexing agent is added to keep the coprecipitation reaction rate of cerium ions and rare earth metal ions consistent, thereby ensuring the uniformity of rare earth metal ion doping. Further preferably, in S2, the complexing agent is selected from at least one of acetylacetone, triethanolamine and citric acid.

[0039] In the present invention, if the dosage of the complexing agent is too low, the concentration of cerium ions and rare earth metal ions cannot be effectively adjusted. If the dosage of the complexing agent is too high, the sedimentation rate of the metal ions will be slow, and the metal ions may not even react with the precipitant to form a precipitate. Under preferred conditions, in S2, in the mixed solution, the molar ratio of the rare earth ions, the cerium ions and the complexing agent is 0.1-0.5:1:0.05-0.25.

[0040] In the present invention, in S3, the organic precipitant should be soluble in the aforementioned organic solvent. Under preferred conditions, the organic precipitant is at least one of propylene oxide and its derivatives; the derivatives of propylene oxide include but are not limited to 2-methylpropylene oxide and epichlorohydrin.

[0041] Preferably, the molar ratio of the rare earth ions, the cerium ions and the organic precipitant is 0.1-0.5:1:1-5.

[0042] In the present invention, if the temperature of the constant temperature standing is too high, it will cause obvious volatilization of the organic solvent, and then lead to the precipitation of the solute (cerium salt and rare earth metal salt). Therefore, the temperature of the constant temperature standing should be lower than the boiling point of the organic solvent. If the temperature of the constant temperature standing is too low, the solubility of the cerium salt and the rare earth metal salt will be reduced, which is also unfavorable for the present invention. In addition, during the standing process, the precursor particles will dissolve and reprecipitate. As the standing time increases, the particle size of the precursor will gradually increase and the particle size will tend to be uniform. Under preferred conditions, in S3, the constant temperature standing conditions include: temperature of 25-60°C and time of 0.5-3h.

[0043] In order to reduce the residual amount of impurity ions in the doped CeO2 powder and improve the conductivity and fluidity of the doped CeO2 powder; under preferred conditions, the method provided by the present invention also includes: washing and drying the precursor, and the washing method can be known to technicians in the field, for example, it can be alcohol washing and / or water washing; in order to improve the washing efficiency, suction filtration or centrifugation can also be performed during the washing process; illustratively, the washing method can be: centrifugally washing the precursor 2-4 times with a solvent of 0.5-3 times the volume of the precursor. The drying method can be known to technicians in the field, for example, the drying temperature is 20-100°C and the time is 2-24h.

[0044] In the present invention, as the annealing temperature increases, the fluidity of the obtained doped CeO2 powder increases, and the ionic conductivity first increases and then decreases. This is because the grains of the powder will gradually grow at high temperatures, and after high-temperature annealing, the surface activity of the powder decreases, so the fluidity becomes better. As the grains grow, the electrolyte grain boundary resistance decreases, the fluidity is enhanced, and the powder is easier to densely stack. Therefore, the conductivity of the powder first decreases as the annealing temperature increases; but as the annealing temperature further increases, the surface activity of the powder decreases, and it becomes more difficult to sinter densely, so the ionic conductivity of the powder decreases when the temperature is too high. Preferably, in S4, the annealing conditions include: a temperature of 500-1200°C and a time of 0.5-5h; more preferably, the annealing temperature is preferably 500-900°C.

[0045] In a preferred embodiment of the present invention, the method for preparing the rare earth oxide doped cerium oxide-based ceramic powder comprises: measuring anhydrous ethanol, adding cerium chloride heptahydrate thereto, keeping the temperature at 60°C and stirring until completely dissolved, weighing samarium chloride and dissolving it completely, taking acetylacetone and dropping it into the above solution and keeping it at 60°C for 1h to modify the metal ion complexation, taking propylene oxide and dropping it into the modified solution while stirring, and continuing to keep the temperature at 60°C for 1h after the addition is completed, and then keeping the temperature at 60°C for 1h to obtain a product precursor, washing the precursor with water and alcohol three times each, and drying at 80°C to obtain a white powder, and keeping the powder at 600°C for 2h to obtain samarium oxide doped cerium oxide ceramic powder;

[0046] The addition ratio of the cerium chloride heptahydrate, samarium chloride, anhydrous ethanol and propylene oxide is 0.048 mol: 0.012 mol: 36 mL: 8 mL.

[0047] The present invention also provides a rare earth oxide-doped cerium oxide-based ceramic powder, which is prepared according to the above method.

[0048] According to the present invention, under preferred conditions, the angle of repose of the rare earth oxide-doped cerium oxide-based ceramic powder is less than 50°; preferably, the electrical conductivity at 750° C. is greater than 0.04 S / cm.

[0049] The present invention also provides an application of the rare earth oxide-doped cerium oxide-based ceramic powder in a solid oxide fuel cell electrolyte.

[0050] The present invention also provides a solid oxide fuel cell, which comprises an anode, an electrolyte and a cathode in sequence; the electrolyte is supported by electrolyte powder and necessary additives, and the electrolyte powder comprises the aforementioned rare earth oxide-doped cerium oxide-based ceramic powder.

[0051] The composition and preparation method of the anode and cathode are known to those skilled in the art, and will not be elaborated herein.

[0052] The present invention is described in detail below with reference to specific embodiments.

[0053] The data in the following table refer to GB / T 21354-2008 for the test method of tap density;

[0054] The test method of the angle of repose refers to GB / T 11986-1989;

[0055] The median particle size is obtained by laser particle size analysis.

[0056] The ionic conductivity test method is to take ceramic powder and granulate it with 3wt% PVA aqueous solution, pour the powder into a mold with a diameter of 13mm, press it into a 3mm disc with an axial pressure of 300MPa, heat it to 1450℃ at 3℃ / min and keep it for 5h to make a disc test sample, collect the current on the disc with silver paste, heat it to 750℃ in an air atmosphere and keep it for 1h, measure the AC impedance of the disc with a two-terminal method, the AC amplitude is 10mV, the frequency range is 106Hz~0.1Hz, and the number of points is 10 points / order of magnitude, so as to obtain the AC impedance spectrum, identify the ohmic resistance of the disc, and calculate the ionic conductivity of the material through the thickness and diameter of the disc.

[0057] Example 1

[0058] 36 mL of anhydrous ethanol was weighed, and 0.048 mol of cerium chloride heptahydrate was added thereto. The mixture was stirred at 60°C until it was completely dissolved. Then 0.012 mol of samarium chloride was weighed and dissolved completely. 0.616 mL of acetylacetone was added dropwise to the above solution and kept at 60°C for 1 h to modify the metal ion complex (total amount of metal ions (Ce 3+ and Sm 3+) and acetylacetone in a molar ratio of 1:0.1), 8 mL of propylene oxide was added dropwise to the modified solution while stirring, and after the addition was completed, the mixture was stirred at a constant temperature of 60°C for 1 hour, and then allowed to stand at a constant temperature of 60°C for 1 hour to obtain a product precursor, and the precursor was washed with water and alcohol three times each, and dried at 80°C to obtain a white powder, and the powder was kept at 600°C for 2 hours to obtain samarium oxide-doped cerium oxide ceramic powder, and the morphology of the product was as follows Figure 1 As shown, from Figure 1 It can be seen that the product prepared in this example has good dispersibility and the primary particles are basically not agglomerated.

[0059] Comparative Example 1

[0060] The difference between this embodiment and embodiment 1 is that the constant temperature standing time is 0.5h to obtain the product precursor, and the rest is exactly the same as embodiment 1. The experimental results are shown in Table 1.

[0061] Example 2

[0062] The difference between this embodiment and embodiment 1 is that the constant temperature standing time is 2 hours to obtain the product precursor, and the rest is exactly the same as embodiment 1. The experimental results are shown in Table 1.

[0063] Comparative Example 2

[0064] The difference between this embodiment and embodiment 1 is that the constant temperature standing time is 3 hours to obtain the product precursor, and the rest is exactly the same as embodiment 1. The experimental results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, with the extension of the standing time, the particle size of the samarium oxide-doped cerium oxide-based ceramic powder gradually increases, the repose angle gradually decreases, and the fluidity gradually increases; the ionic conductivity reaches the maximum value when it is standing for 1 hour. This is because the particles of the precursor will dissolve and reprecipitate during the standing process, and the small particles will gradually disappear during this process. As the standing time increases, the particles will gradually grow, the particle size tends to be uniform, the fluidity of the product increases, but the conductivity decreases.

[0068] Comparative Example 3

[0069] The difference between this embodiment and embodiment 1 is that: 0.0582 mol of cerium chloride heptahydrate is added thereto and stirred at a constant temperature of 60°C until completely dissolved, and then 0.0018 mol of samarium chloride is weighed and completely dissolved, and the rest is exactly the same as in embodiment 1. The experimental results are shown in Table 2.

[0070] In this embodiment, samarium ions account for 3% of the total metal ion concentration.

[0071] Example 3

[0072] The difference between this embodiment and embodiment 1 is that: 0.0552 mol of cerium chloride heptahydrate is added thereto at a constant temperature of 60°C and stirred until completely dissolved, and then 0.0048 mol of samarium chloride is weighed and completely dissolved, and the rest is exactly the same as in embodiment 1. The experimental results are shown in Table 2.

[0073] In this embodiment, samarium ions account for 8% of the total metal ion concentration.

[0074] Example 4

[0075] The difference between this embodiment and embodiment 1 is that: 0.051 mol of cerium chloride heptahydrate is added thereto at a constant temperature of 60°C and stirred until completely dissolved, and then 0.009 mol of samarium chloride is weighed and completely dissolved, and the rest is exactly the same as in embodiment 1. The experimental results are shown in Table 2.

[0076] In this embodiment, samarium ions account for 15% of the total metal ion concentration.

[0077] Example 5

[0078] The difference between this embodiment and embodiment 1 is that: 0.0462 mol of cerium chloride heptahydrate is added thereto at a constant temperature of 60°C and stirred until completely dissolved, and then 0.0138 mol of samarium chloride is weighed and completely dissolved, and the rest is exactly the same as in embodiment 1. The experimental results are shown in Table 2.

[0079] In this embodiment, samarium ions account for 23% of the total metal ion concentration.

[0080] Table 2 Effect of samarium ion doping content on ionic conductivity

[0081] Example No. Samarium ion content Angle of repose Ionic conductivity Example 1 20％ 50° 0.050S / cm Comparative Example 3 3％ 49° 0.034S / cm Example 3 8％ 50° 0.041S / cm Example 4 15％ 51° 0.049S / cm Example 5 23％ 50° 0.047S / cm

[0082] The ionic conductivity of pure cerium oxide is very low and cannot be used as an electrolyte material. When low-valent samarium ions with similar ionic radius are doped into it, charge compensation produces a large number of oxygen vacancies, which improves the ionic conductivity of the material. At the same time, as the concentration of low-valent ions increases, the concentration of oxygen vacancies increases, and the ionic conductivity of the material also increases until it stabilizes. In addition, excessive doping of samarium ions will cause lattice distortion in cerium oxide, and the ionic conductivity will begin to decrease.

[0083] It can be seen from Table 2 that with the increase of samarium ion doping concentration, the ionic conductivity of the product gradually increases; when the samarium ion doping amount is 20%, the ionic conductivity reaches the maximum value and tends to be stable, and the ionic conductivity decreases as the doping amount continues to increase.

[0084] Example 6

[0085] The cerium oxide-based ceramic powder is prepared according to the method of Example 1, except that cerium nitrate hexahydrate is used instead of cerium chloride heptahydrate, and samarium nitrate hexahydrate is used instead of samarium chloride. The specific steps are as follows:

[0086] Measure 36mL of anhydrous ethanol, add 0.048mol of cerium nitrate hexahydrate to it, keep it at 60℃ and stir until it is completely dissolved, then weigh 0.012mol of samarium nitrate hexahydrate and dissolve it completely. Take 0.616mL of acetylacetone and add it dropwise to the above solution and keep it at 60℃ for 1h to modify the metal ion complexation, take 8mL of propylene oxide and add it dropwise to the modified solution while stirring, continue to stir at constant temperature for 1h after the addition is completed, and then keep it at constant temperature for 1h to obtain the product precursor. Wash the precursor with water and alcohol three times each and dry it at 80℃ to obtain a white powder, and keep the powder at 600℃ for 2h to obtain samarium oxide doped cerium oxide ceramic powder.

[0087] The angle of repose of the samarium oxide-doped cerium oxide powder obtained in this example is 50°; and the ionic conductivity is 0.046 S / cm.

[0088] By comparing Example 1 and Example 6, it can be seen that compared with nitrate raw materials (cerium nitrate hexahydrate, samarium nitrate hexahydrate), the samarium oxide doped cerium oxide ceramic powder prepared using chloride salts (cerium chloride heptahydrate, samarium chloride) as raw materials has higher electrical conductivity.

[0089] Example 7

[0090] 36 mL of cyclohexanone was measured, 0.048 mol of cerium chloride heptahydrate was added thereto, the temperature was kept constant at 60°C and stirred until completely dissolved, 0.012 mol of gadolinium chloride was weighed and dissolved completely, 0.796 mL of triethanolamine was added dropwise to the above solution and kept at 80°C for 1 h to modify the metal ion complexation, 8 mL of propylene oxide was added dropwise to the modified solution while stirring, and after the addition was completed, the temperature was kept constant at 60°C for 1 h, and then the product precursor was obtained by standing at 60°C for 1 h. The precursor was washed with water and alcohol three times each, and dried at 80°C to obtain the precursor, and the powder was kept at 600°C for 2 h to obtain yttrium oxide-doped cerium oxide ceramic powder.

[0091] The angle of repose of the gadolinium oxide doped cerium oxide powder obtained in this example is 53°; and the ionic conductivity at 750° C. is 0.046 S / cm.

[0092] Example 8

[0093] The method of Example 1 was followed except that the amount of complexing agent acetylacetone was 3.08 mL, the complexing ratio was 0.5, and the total amount of metal ions (Ce 3+ and Sm 3+) and acetylacetone in a molar ratio of 1:0.5, and the rest is exactly the same as in Example 1.

[0094] Experimental results: After standing at a constant temperature for 7 hours, no precursor precipitation was produced in this example.

[0095] Comparative Example 4

[0096] The samarium oxide doped cerium oxide powder was prepared by coprecipitation method using water as solvent, and the steps are as follows:

[0097] 0.04 mol of cerium nitrate hexahydrate and 0.01 mol of samarium nitrate hexahydrate were dissolved in 500 mL of water to prepare a mixed solution with a total concentration of cerium nitrate and samarium nitrate of 0.1 mol / L. 0.125 mol of ammonium carbonate was weighed and dissolved in 1.25 L of water as a precipitant. The mixed solution was added dropwise to the precipitant while stirring at room temperature. After the addition was completed, the product precursor was allowed to stand at room temperature for 2 h. The precursor was centrifuged and washed with water and alcohol for three times each, and then dried at 80°C to obtain a precursor powder. The powder was kept at 600°C for 2 h to obtain samarium oxide-doped cerium oxide ceramic powder prepared by co-precipitation method. The experimental results are shown in Table 3. The morphology of the product is shown in Figure 2 shown.

[0098] from Figure 2 It can be seen that the product prepared in this comparative example is an agglomerate formed by agglomeration of nano-scale primary particles.

[0099] Comparative Example 5

[0100] The samarium oxide doped cerium oxide powder is prepared by combustion method, and the specific steps are as follows:

[0101] Take 200mL of deionized water and heat it to 50°C. Add 0.125mol of glycine, 0.05mol of citric acid, 0.04mol of cerium nitrate hexahydrate and 0.01mol of samarium nitrate hexahydrate in sequence while stirring. In this process, wait until the former powder is completely dissolved before adding the latter powder. After all the powders are dissolved, stir at a constant temperature of 50°C for 2h. Then heat the solution to boiling to evaporate the solvent. The solution gradually becomes viscous and resembles a gel. Continue to heat until the gel spontaneously ignites and sprays out a light yellow powder. Keep the powder at 600°C for 2h to obtain samarium oxide-doped cerium oxide ceramic powder prepared by the glycine combustion method. The difference from Example 1 lies in the difference in the preparation method. The experimental results are shown in Table 3. The morphology of the product is as shown in Table 3. Figure 3 shown.

[0102] Table 3

[0103] Experimental methods Tap density Angle of repose Ionic conductivity Example 1 Organic solvent coprecipitation <![CDATA[0.94g / cm 3 ]]> 50° 0.050S / cm Comparative Example 4 Water-coprecipitation <![CDATA[0.625g / cm 3 ]]> 54° 0.039S / cm Comparative Example 5 Combustion method <![CDATA[0.094g / cm 3 ]]> 70° 0.037S / cm

[0104] It can be seen from the data in Table 3 that, compared with the traditional co-precipitation method and combustion method, the samarium oxide-doped cerium oxide-based ceramic powder prepared by Example 1 and Comparative Example 3 of the present invention has higher ionic conductivity and better fluidity.

[0105] Comparative Example 6

[0106] The difference between this embodiment and embodiment 1 is that the powder is kept at 400° C. for 2 hours to obtain samarium oxide-doped cerium oxide ceramic powder, and the rest is exactly the same as embodiment 1.

[0107] Comparative Example 7

[0108] The difference between this embodiment and embodiment 1 is that the powder is kept at 1000° C. for 2 hours to obtain samarium oxide-doped cerium oxide ceramic powder, and the rest is exactly the same as embodiment 1.

[0109] Comparative Example 8

[0110] The difference between this embodiment and embodiment 1 is that the powder is kept at 1100° C. for 2 hours to obtain samarium oxide-doped cerium oxide ceramic powder, and the rest is exactly the same as embodiment 1.

[0111] Table 4 Effect of annealing temperature on powder properties

[0112] Example No. Annealing temperature Tap density Angle of repose Ionic conductivity Example 1 600℃ <![CDATA[0.94g / cm 3 ]]> 50° 0.050S / cm Comparative Example 6 400℃ <![CDATA[0.63g / cm 3 ]]> 61° 0.044S / cm Example 10 1000℃ <![CDATA[1.2g / cm 3 ]]> 30° 0.028S / cm Embodiment 11 1100℃ <![CDATA[1.3g / cm 3 ]]> 28° 0.022S / cm

[0113] It can be seen from Table 4 that with the increase of annealing temperature, the fluidity of the powder increases, and the ionic conductivity first increases and then decreases. This is because the grains of the powder will gradually grow at high temperature, and the surface activity of the powder decreases after high-temperature annealing, so the fluidity becomes better. As the grains grow, the electrolyte grain boundary resistance decreases, the fluidity is enhanced, and the powder is easier to densely stack. Therefore, the conductivity of the powder first decreases with the increase of annealing temperature; but as the annealing temperature further increases, the surface activity of the powder decreases and it becomes more difficult to sinter densely, so the ionic conductivity of the powder decreases when the temperature is too high. Preferably, annealing at 600°C is selected.

[0114] Depend on Figure 1 , Figure 2 and Figure 3 By comparison, it can be observed that different preparation methods have a great influence on the morphology of the powder. Compared with the traditional method, the powder prepared in Example 1 has a uniform particle size and is not agglomerated, and has good dispersibility.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing rare earth oxide-doped cerium oxide-based ceramic powder, characterized in that: The following steps are involved: S1, dissolving a cerium source and a rare earth source in an organic solvent, and stirring to obtain a mixed solution; S2, adding a complexing agent to the mixed solution and mixing evenly to obtain a mixed system; The complexing agent is selected from at least one of acetylacetone, triethanolamine and citric acid; in the mixed solution, the molar ratio of the rare earth ions in the rare earth source, the cerium ions in the cerium source and the complexing agent is 0.1-0.5:1:0.05-0.25; S3, adding an organic precipitant to the mixed system, and keeping it at a constant temperature to obtain a precursor; The organic precipitant is at least one of propylene oxide and its derivatives; The molar ratio of the rare earth ions in the rare earth source, the cerium ions in the cerium source and the organic precipitant is 0.1-0.5:1:1-5; The conditions for the constant temperature static state include: temperature of 25-60°C and time of 0.5-3h; S4, annealing the precursor to obtain a rare earth oxide-doped cerium oxide-based ceramic powder; The rare earth source is selected from at least one of a lanthanum source, a praseodymium source, a neodymium source, a promethium source, a samarium source, a europium source, a gadolinium source, a terbium source, a dysprosium source, a holmium source, an erbium source, a thulium source, a ytterbium source, a lutetium source, a scandium source and a yttrium source.

2. The method according to claim 1, characterized in that In S1, the cerium source is selected from inorganic cerium salts.

3. The method according to claim 2, characterized in that In S1, the inorganic cerium salt is selected from at least one of cerium nitrate hexahydrate, cerium chloride heptahydrate, ammonium cerium nitrate, cerium sulfate, ammonium cerium sulfate and cerium acetate.

4. The method according to claim 1, characterized in that: In S1, the rare earth source is selected from at least one of a neodymium source, a promethium source, a samarium source, a europium source and a gadolinium source.

5. The method according to claim 1, characterized in that In S1, the rare earth source is selected from at least one of rare earth metal nitrates, rare earth metal chlorides, rare earth metal sulfates and rare earth metal acetates.

6. The method according to claim 1, characterized in that In S1, the organic solvent is selected from at least one of methanol, ethanol, propanol, ethylene glycol, dimethyl sulfoxide, dimethylformamide acetone, acetone, cyclohexanone and 2-butanone.

7. The method according to claim 1, characterized in that In S1, the rare earth ion concentration in the rare earth source accounts for 3%-20% of the total metal ion concentration, and the total metal ion concentration is the sum of the rare earth ion concentration in the rare earth source and the cerium ion concentration in the cerium source.

8. The method according to claim 1, characterized in that: In the step S4, the annealing conditions include: a temperature of 500-1200° C. and a time of 0.5-5 h.

9. A rare earth oxide-doped cerium oxide-based ceramic powder, characterized in that: Prepared according to the method according to any one of claims 1 to 8.

10. The rare earth oxide-doped cerium oxide-based ceramic powder according to claim 9, characterized in that: The angle of repose of the rare earth oxide-doped cerium oxide-based ceramic powder is less than 50°.

11. The rare earth oxide-doped cerium oxide-based ceramic powder according to claim 9 or 10, characterized in that: The electrical conductivity of the rare earth oxide-doped cerium oxide-based ceramic powder at 750° C. is greater than 0.04 S / cm.

12. Use of the rare earth oxide-doped cerium oxide-based ceramic powder according to any one of claims 9 to 11 in a solid oxide fuel cell electrolyte.

13. A solid oxide fuel cell comprising the electrolyte according to claim 12.

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