A reverse coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ Core-shell structured composite ceramic and method for preparing the same

Abstract

The application discloses a reverse-coated BaCe 1‑ x Gd x O 3‑δ @Ce 1‑x Gd x O 2‑δ Nuclear shell structure composite ceramic and preparation method thereof belong to the field of solid electrolyte materials. The application takes (CH3COO)2Ba, Ce(NO3)3.6H2O and Gd(NO3)3.6H2O as raw materials, drops a precipitator and a surfactant, mixes the obtained solution with Ce(NO3)3.6H2O and Gd(NO3)3.6H2O precursor solution, adds a precipitator and a dispersant, pre-calcines to obtain a nuclear shell powder, adds a binder, and sinter to obtain BaCe 1‑x Gd x O 3‑δ @Ce 1‑ x Gd x O 2‑δ Nuclear shell structure composite ceramic. The application improves the BCG / DGC two-phase interface ratio and the continuity of two phases by constructing a nuclear shell structure, taking BCG as an inner core and GDC as an outer shell, constructs a high-speed channel of ion transmission, and improves ion conductivity. The application uses (NH4)2CO3 as a new type of precipitator, obtains more fine nuclear shell structure composite ceramic powder, promotes the sintering densification of the nuclear shell structure ceramic block, and prepares the BCG@GDC nuclear shell structure composite ceramic with high ion conductivity. The conductivity of the BCG@GDC nuclear shell structure composite ceramic can reach 1.07*10 ‑2 S / cm under the air atmosphere at 600 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid electrolyte materials, in particular to a reverse coated BaCe 1-x Gd x O 3-δ @Ce 1- x Gd x O 2-δ Core-shell structure composite ceramic and preparation method thereof. BACKGROUND

[0002] CeO2 is an important oxygen ion conductor solid electrolyte. Research has found that CeO2 doped with rare earth ions or alkaline earth metal ions has high ion conductivity, but it has certain electronic conductivity in a reducing atmosphere, which causes certain deterioration of the performance of the battery. In CeO2 electrolyte doped with rare earth ions, Ce 0.8 Sm 0.2 O 1.95 (SDC) and Ce 0.9 Gd 0.1 O 1.95 (GDC) are considered to be the most promising solid electrolytes to replace YSZ for use in intermediate-temperature solid oxide fuel cells (IT-SOFC), oxygen separation membranes, and oxygen sensors, etc.

[0003] BaCeO3-based ceramics are a typical proton conductor, which exhibits unique advantages in solid oxide fuel cells, oxygen sensors, catalysis, and many other fields. In order to improve its electrical conductivity and improve its stability in acidic and steam environments, rare earth element doping is generally used to optimize its performance. BaCeO3 proton conductor electrolytes doped with different elements are considered to be the most promising electrolytes to replace YSZ oxygen ion conductors. However, BaCeO3 is easily reacted with H2O and CO2 in air to generate Ba(OH)2, BaCO3, and CeO2, thereby restricting its application.

[0004] Currently, there have been reports on the preparation of core-shell structure composite ceramics with BaCe 0.9 Gd 0.1 O 2.95 (BCG) as the outer shell and Ce 0.8 Gd 0.2 O 1.9 (GDC) as the inner core. Although the core-shell structure improves the grain boundary conductivity of GDC, the sintering density of the outer shell BCG is low, which leads to difficulties in sintering of the GDC@BCG core-shell structure composite ceramic and low density, resulting in a decrease in the effective ion transport cross section, destroying the continuity of the material structure, and making the ion conduction in the material need to bypass these obstacles, thereby greatly increasing the path length of ion conduction.

[0005] Therefore, by constructing the core-shell structure, improving the BCG / GDC two-phase interface ratio, forming the high-speed channel of ion transmission further improves the conductivity, and solves the disadvantages of the two-phase interface separation, discontinuity and uneven distribution of the traditional mechanical mixed BCG and GDC. SUMMARY

[0006] The application uses a new type of (NH4)2CO3 as a precipitant to synthesize core-shell structure powder by a coprecipitation method, and the powder with smaller grain size improves the BCG / GDC two-phase interface ratio, and the core-shell structure composite ceramic is formed by conventional sintering.

[0007] The application discloses a reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ Embodiment of the core-shell structure composite ceramic, comprising the following steps:

[0008] (1) mixing (CH3COO)2Ba, Ce(NO3)3.6H2O and Gd(NO3)3.6H2O, then dissolving in water, adding (NH4)2CO3, CH3(CH2) 11 C6H4SO3Na in sequence, and finally obtaining solution A;

[0009] (2) mixing Ce(NO3)3.6H2O and Gd(NO3)3.6H2O, then dissolving in water to obtain a precursor solution;

[0010] (3) adding the precursor solution into solution A, uniformly mixing, adding NH3.H2O until precipitation is complete, ultrasonic dispersion, continuously adding polyvinylpyrrolidone and stirring, sequentially performing washing, centrifugation, drying, drying the obtained precursor powder, pre-calcining to obtain core-shell powder, then adding polyvinyl alcohol, tabletting, sintering to obtain BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ core-shell structure composite ceramic.

[0011] Preferably, as an embodiment of the application, the molar ratio of (CH3COO)2Ba, Ce(NO3)3.6H2O and Gd(NO3)3.6H2O in step (1) is 1:(0.8-0.9):(0.1-0.2).

[0012] Preferably, as an embodiment of the application, (NH4)2CO3, (CH3COO)2Ba and CH3(CH2) 11The molar ratio of C6H4SO3Na is (1-1.5):1:(0.1-0.2).

[0013] Preferably, as an embodiment of the present application, the molar ratio of Ce(NO3)3.6H2O and Gd(NO3)3.6H2O used in the step (2) is (0.8-0.9):(0.1-0.2).

[0014] Preferably, as an embodiment of the present application, the CH3(CH2) 11 C6H4SO3Na is used as a surfactant.

[0015] Preferably, as an embodiment of the present application, the molar ratio of polyvinylpyrrolidone and (CH3COO)2Ba is (0.3-0.4):1.

[0016] Preferably, as an embodiment of the present application, the molar ratio of Ce 3+ in the precursor solution in the step (2) and Ba 2+ in the solution A is (0.8-0.9):1.

[0017] Preferably, as an embodiment of the present application, the stirring time in the step (3) is 10-12h.

[0018] Preferably, as an embodiment of the present application, the drying temperature in the step (3) is 100-120℃, and the drying time is 10-20h.

[0019] Preferably, as an embodiment of the present application, the pre-calcination temperature in the step (3) is 800-900℃, and the pre-calcination time is 5-6h.

[0020] Preferably, as an embodiment of the present application, the polyvinyl alcohol is added in the step (3) to achieve powder bonding and better tabletting effect.

[0021] Preferably, as an embodiment of the present application, the sintering temperature in the step (3) is 1500-1600℃, and the holding time is 9-12h.

[0022] The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ The reverse-coated BaCe 1-x Gd x O 3-δ@Ce 1- x Gd x O 2-δ core-shell powder, combined with conventional sintering to obtain a core-shell structure composite ceramic, the chemical formula of which is BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ (BCG@GDC), wherein x=0.1-0.2 and δ=0-0.1.

[0023] The core-shell structure described in the application increases the proportion of the BCG and GDC two-phase interface, improves the continuity of the two phases, constructs a high-speed channel for ion transmission to further improve the electrical conductivity, compared with the traditional mechanical mixing of the BCG and GDC core-shell structure, solves the disadvantages of two-phase interface separation, discontinuity and uneven distribution. The coating of GDC on BCG and the joint action of the new type of precipitating agent effectively prevent BaCeO3 from reacting with H2O and CO2 in the air to generate Ba(OH)2 and BaCO3, which hinders ion transmission.

[0024] The GDC shell with better sintering density and the BCG inner core with poor sintering performance described in the application are reversely coated, which can improve the sintering density of the BCG@GDC composite ceramic, so that the internal structure of the material with high density is more compact and regular, and the problems of pores, cavities and defects are relatively less, thereby providing a more direct and smooth path for ion conduction. Ions can move along the relatively continuous lattice structure in the material, without frequently bypassing a large number of pores and defects as in the material with low density, thereby greatly shortening the path length of ion conduction.

[0025] The application has the following beneficial effects:

[0026] (1) The core-shell structure constructed in the application improves the sintering density of the BCG@GDC composite ceramic, the internal structure of the material with high density is more compact and regular, and the problems of pores, cavities and defects are relatively less, thereby providing a more direct and smooth ion conduction path, without frequently bypassing a large number of pores and defects as in the material with low density, thereby greatly shortening the path length of ion conduction. By constructing the core-shell structure, the proportion of the BCG / GDC two-phase interface is increased, the continuity of the two phases is further improved, a high-speed channel for ion transmission is constructed to further improve the electrical conductivity, and the coating of GDC on BCG can effectively prevent BaCeO3 from reacting with H2O and CO2 in the air to generate Ba(OH)2.

[0027] (2) In the core-shell structure constructed in this invention, the excellent sintering characteristics of GDC can promote grain growth and densification during the sintering process. When GDC is coated on the surface of BCG, the GDC coating layer densifies to a certain extent before BCG during the high-temperature sintering stage, forming a skeleton-like structure that provides support for the internal BCG, restricts the abnormal growth of BCG grains, and effectively fills the pores between BCG grains, thereby significantly improving the overall sintering density of the material. Compared with uncoated BCG ceramics, the density can be increased by 3% to 5%, greatly improving the uniformity of the material's microstructure.

[0028] (3) The preparation method of the present invention uses a novel (NH4)2CO3 as a precipitant, wherein the molar ratio of (NH4)2CO3 to (CH3COO)2Ba is 1:(1~1.5), which can obtain BaCO3 that is insoluble in water, avoid loss during washing and centrifugation, and effectively ensure the existence of BCG and GDC phases. The preparation method is simple and economical.

[0029] (4) The core-shell structured nanoparticles prepared by this invention have a near-spherical grain shape, which helps to construct a two-phase interface and thus improves electrical conductivity. The electrical conductivity in air at 600℃ can reach 1.07×10⁻⁶. -2 S / cm.

[0030] (5) This invention constructs BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ The core-shell structure, with the interface between BCG and GDC serving as H + and O 2- The high-speed channels improve the conductivity of the multiphase ceramic, and the BCG and GDC core-shell structures can also achieve a higher interface ratio, thereby improving the conductivity of the multiphase electrolyte. Attached Figure Description

[0031] Figure 1 BaCe prepared in Example 1 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ XRD pattern of core-shell structured powder.

[0032] Figure 2 BaCe prepared in Example 1 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O2-δ SEM image of core-shell structure powder and grain distribution, (a) is BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ SEM image of core-shell structure powder; (b) is BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ Normal distribution of core-shell structure powder grain.

[0033] Figure 3 BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ TEM image of core-shell structure powder.

[0034] Figure 4 BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ AC impedance diagram of core-shell structure composite ceramic.

[0035] Figure 5 BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ XRD diagram of core-shell structure powder.

[0036] Figure 6 BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ SEM image of core-shell structure powder and grain distribution, (a) is BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δSEM image of core-shell structured powder; (b) BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ Gaussian curve of grain distribution of core-shell structured powder.

[0037] Figure 7 SEM image of core-shell structured powder; (b) BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ TEM image of core-shell structured powder.

[0038] Figure 8 SEM image of core-shell structured powder; (b) BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ Impedance plot of core-shell structured composite ceramic.

[0039] Figure 9 SEM image of core-shell structured powder; (b) BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ XRD pattern of core-shell structured powder.

[0040] Figure 10 SEM image of core-shell structured powder; (b) BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ SEM image of core-shell structured powder and grain distribution diagram (a) BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ SEM image of core-shell structured powder; (b) BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ Gaussian normal distribution diagram of core-shell structured powder.

[0041] Figure 11 BaCe prepared for Comparative Example 1 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ AC impedance diagram of core-shell structured multiphase ceramics.

[0042] Figure 12 BaCe prepared for Comparative Example 2 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ AC impedance diagram of core-shell structured multiphase ceramics.

[0043] Figure 13 BaCe prepared for Comparative Example 3 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ XRD pattern of core-shell structured powder.

[0044] Figure 14 Ce obtained for Comparative Example 4 0.8 Gd 0.2 O 2-δ @BaCe 0.8 Gd 0.2 O 3-δ AC impedance diagram of core-shell ceramics.

[0045] Figure 15 The reverse coating of BaCe described in this invention 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ Flowchart of the preparation process of core-shell structured multiphase ceramics. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0047] Example 1

[0048] A reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δA method for preparing a core-shell structure composite ceramic, comprising the following steps:

[0049] (1) 0.01 mol (CH3COO)2Ba, 0.008 mol Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O are mixed and dissolved in 100 mL of distilled water, 0.2 mol / L (NH4)2CO3 solution is slowly added dropwise, and 0.02 mol / L CH3(CH2) 11 Solution A is obtained by dissolving in C6H4SO3Na solution.

[0050] (2) 0.008 mol Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O are dissolved in 100 mL of distilled water to obtain a precursor solution.

[0051] (3) The precursor solution is slowly added dropwise into solution A, fully stirred, precipitated by slowly adding NH3·H2O, fully ultrasonically dispersed, then slowly added dropwise into 0.08 mol / L polyvinylpyrrolidone solution, stirred for 10 h, washed with anhydrous ethanol, centrifuged, stirred, and then dried at 100°C for 10 h, the finally obtained precursor powder is precalcined at 850°C for 5 h to obtain BCG@GDC core-shell structure powder, a drop of polyvinyl alcohol binder is added, pressed into a sheet, sintered at 1500°C for 9 h, and a reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic is obtained.

[0052] Example 2

[0053] A reverse-coated BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ core-shell structure composite ceramic is obtained.

[0054] (1) 0.01 mol (CH3COO)2Ba, 0.009 mol Ce(NO3)3·6H2O, 0.001 mol Gd(NO3)3·6H2O are mixed and dissolved in 100 mL of distilled water, 0.2 mol / L (NH4)2CO3 solution is slowly added dropwise, and 0.02 mol / L CH3(CH2) 11 Solution A is obtained by dissolving in C6H4SO3Na solution.

[0055] (2) 0.009 mol Ce(NO3)3·6H2O, 0.001 mol Gd(NO3)3·6H2O were dissolved in 100 mL distilled water to obtain a mixed precursor solution.

[0056] (3) The precursor solution was slowly dripped into solution A, fully stirred, precipitated by slowly adding NH3·H2O, fully ultrasonic dispersed, then slowly dripped into 0.08 mol / L polyvinylpyrrolidone solution, stirred for 10 h, washed with anhydrous ethanol, centrifuged, stirred, then dried at 100 ℃ for 10 h, the finally obtained precursor powder was pre-calcined at 800 ℃ for 5 h to obtain BCG@GDC core-shell structure powder, a drop of polyvinyl alcohol binder was added, pressed into a tablet, then sintered at 1500 ℃ for 9 h to obtain reverse coated BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ core-shell structure composite ceramic.

[0057] Example 3

[0058] A preparation method of reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic, comprising the following steps:

[0059] (1) 0.01 mol (CH3COO)2Ba, 0.008 mol Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O were mixed and dissolved in 100 mL distilled water, 0.2 mol / L (NH4)2CO3 solution was slowly dripped, 0.02 mol / L CH3(CH2) 11 C6H4SO3Na solution was obtained to obtain solution A.

[0060] (2) 0.008 mol Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O were dissolved in 100 mL distilled water to obtain a precursor solution.

[0061] (3) precursor solution is slowly dripped into solution A, fully stirred, precipitated slowly adding NH3·H2O, fully ultrasonic dispersion, then slowly dripped into 0.08 mol / L polyvinylpyrrolidone solution, stirring 10 h, washed with anhydrous ethanol, centrifuged, stirred and dried at 100℃ for 10 h, the finally obtained precursor powder is precalcined at 900℃ for 5 h to obtain BCG@GDC core-shell structure powder, a drop of polyvinyl alcohol binder is added, tabletting is carried out and sintering is carried out at 1500℃ for 9 h, to obtain reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure powder.

[0062] The BCG@GDC core-shell structure powder prepared in Example 1-2 is subjected to XRD test, from Figure 1 which it can be known that the BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure powder prepared in Example 1 has no impurity phase, the diffraction peaks of BCG and GDC can be obviously seen, and the desired substance can be produced according to the predetermined design, thus it can be seen that the design of the present application is reasonable. 3+ When the precalcination temperature is lowered and the molar ratio of Ce 3+ to Gd Figure 5 is increased, from which it can be known that the BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ core-shell structure powder prepared in Example 2 has impurity peaks but the diffraction peaks of BCG and GDC can be obviously seen, thus it can be seen that the design of the present application is reasonable, and the desired substance can be produced according to the predetermined design.

[0063] The BCG@GDC core-shell structure powder prepared in Example 1-2 is subjected to SEM analysis, as Figure 2 shown, the BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure powder prepared in Example 1 basically follows normal distribution, and the average grain size is 49 nm; as Figure 6 shown, the BaCe 0.9 Gd 0.1O 3-δ @Ce 0.9 Gd 0.1 O 2-δ The core-shell structure powder has a grain distribution according to a Gaussian curve, and an average grain size of 44 nm.

[0064] TEM analysis was performed on the BCG@GDC core-shell structure powder prepared in Examples 1-2. The BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ TEM analysis results of the core-shell structure powder are shown in Figure 3 The lattice fringes of BCG and GDC can be clearly observed, and it can be clearly seen that BCG is coated by GDC. The BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ TEM analysis results of the core-shell structure powder are shown in Figure 7 The lattice fringes of BCG and GDC can be clearly observed, and it can be clearly seen that BCG is coated by GDC.

[0065] The BCG@GDC core-shell structure ceramic prepared in Examples 1-2 was subjected to 600°C AC impedance testing under air atmosphere. According to equivalent circuit fitting, the results are shown in Figure 4 The conductivity is 1.07 x 10 -2 S / cm. The BaCe 0.9 Gd 0.1 O 3-δ @Ce 0.9 Gd 0.1 O 2-δ The core-shell structure composite ceramic was subjected to 600°C AC impedance testing under air atmosphere. According to equivalent circuit fitting, the results are shown in Figure 8 The conductivity is 1.05 x 10 -2 S / cm.

[0066] The BCG@GDC core-shell structure ceramic prepared in Examples 1-2 was subjected to density testing by Archimedes drainage method, and the relative density was 95-96.2%. The conductivity and density of the BCG@GDC core-shell structure ceramic prepared in Example 3 were similar to those of the BCG@GDC core-shell structure ceramic prepared in Examples 1-2.

[0067] Comparative Example 1

[0068] A reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ A preparation method of core-shell structure composite ceramic, the specific steps are as follows:

[0069] (1) 0.01 mol (CH3COO)2Ba, 0.008 mol Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O are weighed and dissolved in 100 mL distilled water, NH3·H2O is slowly added until the pH of the solution is 8-10, and 0.02 mol / L CH3(CH2) 11 C6H4SO3Na solution is obtained.

[0070] (2) 0.008 mol (Ce(NO3)3·6H2O, 0.002 mol Gd(NO3)3·6H2O are weighed and dissolved in 100 mL distilled water to obtain a precursor solution.

[0071] (3) The precursor solution is slowly added to solution A and stirred, NH3·H2O is added for precipitation and ultrasonic dispersion, then 0.08 mol / L polyvinylpyrrolidone solution is slowly added, stirred for 10 h, the obtained suspension is stirred and placed in a drying box at 100°C for 10 h, the obtained precursor powder is precalcined at 850°C for 5 h to obtain BCG@GDC core-shell structure powder, a drop of polyvinyl alcohol binder is added, pressed into a sheet, sintered at 1500°C for 9 h to obtain a reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic.

[0072] Comparative example 2

[0073] A reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic.

[0074] (1) Take 0.01 mol (CH3COO)2Ba, 0.008 mol Ce (NO3)3·6H2O, 0.002 mol Gd (NO3)3·6H2O, mix and dissolve in 100 mL distilled water, slowly drop NH3·H2O until the solution pH is 8-10, continue to slowly drop 0.02 mol / L CH3 (CH2) 11 C6H4SO3Na solution to obtain solution A.

[0075] (2) Take 0.008 mol Ce (NO3)3·6H2O, 0.002 mol Gd (NO3)3·6H2O, dissolve in 100 mL distilled water to obtain a precursor solution.

[0076] (3) Slowly drop the precursor solution into solution A and stir well, add NH3·H2O to precipitate and disperse well by ultrasonic, slowly drop into 0.08 mol / L polyvinylpyrrolidone solution, stir for 10 h, put the obtained suspension into a drying oven at 100 ℃ for 10 h to obtain dry precursor powder, continue to pre-calcine at 800 ℃ for 5 h to obtain BCG@GDC core-shell structure powder, add one drop of polyvinyl alcohol binder, press into a tablet, sinter at 1500 ℃ for 9 h to obtain reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic.

[0077] Comparative Example 3

[0078] A reverse coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure ceramic and a preparation method thereof, the specific steps are as follows:

[0079] (1) Take 0.01 mol (CH3COO)2Ba, 0.008 mol Ce (NO3)3·6H2O, 0.002 mol Gd (NO3)3·6H2O, mix and dissolve in 100 mL distilled water, slowly drop NH3·H2O until the solution pH is 8-10, continue to slowly drop 0.02 mol / L CH3 (CH2) 11 C6H4SO3Na solution to obtain solution A.

[0080] (2) Take 0.008 mol of Ce(NO3)3·6H2O and 0.002 mol of Gd(NO3)3·6H2O according to the stoichiometric ratio, and dissolve them in an appropriate amount of distilled water to obtain a precursor solution.

[0081] (3) Slowly drop the precursor solution into solution A, fully stir, add NH3·H2O again for precipitation, fully ultrasonic dispersion, slowly drop into a 0.08 mol / L polyvinylpyrrolidone solution, stir for 10 h to obtain a suspension, wash with anhydrous ethanol, centrifuge, stir, and then put into a drying box at 100℃ for 10 h. Dry the dried precursor powder, calcine it at 900℃ for 5 h to obtain BCG@GDC core-shell structure powder. Add one drop of polyvinyl alcohol binder, press the tablet, sinter at 1500℃ for 9 h to obtain reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ core-shell structure composite ceramic.

[0082] Comparative Example 4

[0083] A preparation method of a forward-coated Ce 0.8 Gd 0.2 O 2-δ @BaCe 0.8 Gd 0.2 O 3-δ core-shell structure composite ceramic, and the specific steps are as follows:

[0084] (1) Take 0.01 mol of (CH3COO)2Ba, 0.008 mol of Ce(NO3)3·6H2O, and 0.002 mol of Gd(NO3)3·6H2O, mix them in 100 mL of distilled water to obtain a precursor solution.

[0085] (2) Take 0.008 mol of Ce(NO3)3·6H2O and 0.002 mol of Gd(NO3)3·6H2O, dissolve them in 100 mL of distilled water, mix well, slowly drop in NH3·H2O until the pH value of the solution is 8-10, and continue to slowly drop in 0.02 mol / L CH3(CH2) 11 C6H4SO3Na solution to obtain solution A.

[0086] (3) The precursor solution was slowly added dropwise to solution A, stirred thoroughly, and NH3·H2O was added again for precipitation. After thorough ultrasonic dispersion, it was slowly added dropwise to a 0.08 mol / L polyvinylpyrrolidone solution and stirred for 10 h to obtain a suspension. After stirring, it was placed in a drying oven and dried at 100℃ for 10 h to obtain the dried precursor powder. It was then calcined at 850℃ for 5 h to obtain GDC@BCG core-shell structure powder. One drop of polyvinyl alcohol binder was added, and after tableting, it was sintered at 1500℃ for 9 h to obtain positively coated Ce. 0.8 Gd 0.2 O 2-δ @BaCe 0.8 Gd 0.2 O 3-δ Core-shell structured multiphase ceramics.

[0087] Example of effect

[0088] The BCG@GDC core-shell structured nanopowders prepared in Comparative Examples 1 and 3 were subjected to XRD tests, and the results are as follows: Figure 9 As shown, the reverse-coated BaCe prepared in Comparative Example 1 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ The core-shell structured powder, due to the use of NH3·H2O as a precipitant, only precipitated a small amount of BCG, resulting in weak diffraction peaks of BCG in the XRD pattern, with almost no visible peaks. This indicates that the core-shell structured powder contains only a small amount of BCG, which is not conducive to the construction of the core-shell structure. Comparative Example 3 prepared reverse-coated BaCe... 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ Core-shell structured powder, from Figure 13 As can be seen, there are only diffraction peaks of GDC and no diffraction peaks of BCG, indicating that the prepared sample contains only GDC.

[0089] The reverse-coated BaCe prepared in Comparative Example 1 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ SEM analysis of core-shell structured powders, such as... Figure 10 As shown, its grains are basically distributed normally, with an average grain size of 88 nm.

[0090] The positively coated Ce prepared in Comparative Example 4 0.8 Gd 0.2 O2-δ @BaCe 0.8 Gd 0.2 O 3-δ The core-shell structure composite ceramic was tested for density by Archimedes drainage method, and the relative density was 92%.

[0091] The core-shell structure composite ceramic prepared from Comparative Example 1-4 was subjected to alternating current impedance test at 600°C under air atmosphere, and the equivalent circuit was fitted according to Figure 11 The reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ The conductivity of the core-shell structure ceramic was 0.58×10 -2 S / cm. Figure 12 The reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ The conductivity of the core-shell structure ceramic was 0.68×10 -2 S / cm. Figure 14 The forward-coated Ce 0.8 Gd 0.2 O 2-δ @BaCe 0.8 Gd 0.2 O 3-δ The conductivity of the core-shell structure ceramic was 0.7×10 -2 S / cm; compared with Examples 1-3, the reverse-coated BaCe 0.8 Gd 0.2 O 3-δ @Ce 0.8 Gd 0.2 O 2-δ The conductivity of the core-shell structure ceramic was relatively poor. Through comparison of Examples 1-3 and Comparative Examples 1-4, it was found that the preparation method of the application could indeed obtain BCG@GDC core-shell structure ceramic with higher conductivity and finer grain size.

[0092] It is found by comparing examples 1-3 with comparative examples 1-4 that the preparation method provided by the application can obtain BCG and GDC two phases, and help to construct the core-shell structure, and obtain BCG@GDC core-shell structure ceramic with higher conductivity. When (NH4)2CO3 is used as the precipitant, the obtained BaCO3 precipitate which is hardly soluble in water is beneficial to the precipitation of BCG phase, improves the BCG / GDC two phase ratio, improves the continuity of the two phases, and the ion transmission channel formed further improves the conductivity. Secondly, the GDC coating on the BCG improves the sintering densification of the BCG@GDC composite ceramic, the internal structure of the material with high densification is more compact and regular, and the porosity, cavity and defects are relatively less. Compared with the uncoated BCG ceramic, the densification can be improved by 3% to 5%, and the microstructure uniformity of the material is greatly improved.

[0093] The above only describes the preferred embodiments of the application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ core-shell structure composite ceramic, characterized by, The method comprises the following steps: (1) (CH3COO)2Ba, Ce(NO3)3-6H2O and Gd(NO3)3-6H2O were mixed and dissolved in water, (NH4)2CO3, CH3(CH2) 11 C6H4SO3Na were added in sequence to obtain solution A; (2) mixing Ce(NO3)3·6H2O and Gd(NO3)3·6H2O and dissolving them in water to obtain a precursor solution; (3) adding the precursor solution into solution A, adding NH3-H2O until precipitation is complete after mixing uniformly, dispersing by ultrasonic, continuing to add polyvinylpyrrolidone and stirring, sequentially performing washing, centrifuging, drying, drying the obtained precursor powder, pre-calcining to obtain a core-shell powder, then adding polyvinyl alcohol, tabletting, and sintering to obtain BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ Core-shell structure composite ceramic, wherein x = 0.1-0.2, and δ = 0-0.

1.

2. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The molar ratio of (CH3COO)2Ba, Ce(NO3)3·6H2O and Gd(NO3)3·6H2O in step (1) is 1:(0.8-0.9):(0.1-0.2).

3. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The molar ratio of (NH4)2CO3, (CH3COO)2Ba and CH3(CH2) 11 The molar ratio of C6H4SO3Na, (NH4)2CO3 and CH3(CH2) 4. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The molar ratio of Ce(NO3)3·6H2O and Gd(NO3)3·6H2O in step (2) is (0.8-0.9):(0.1-0.2).

5. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The Ce in the precursor solution in the step (2) 3+ The molar ratio of Ba in solution A 2+ to the molar ratio of (0.8-0.9):

1.

6. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ Method for preparing a core-shell structured composite ceramic, characterized in that, The molar ratio of polyvinylpyrrolidone and (CH3COO)2Ba in step (3) is (0.3-0.4):

1.

7. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The precalcination temperature in step (3) is 800-900℃, and the precalcination time is 5-6h.

8. The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ A method for preparing a core-shell structure composite ceramic, characterized in that, The sintering temperature in step (3) is 1500-1600℃, and the sintering time is 9-12h.

9. The reverse-coated BaCe according to any one of claims 1-8 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ The preparation method of the core-shell structure composite ceramic The reverse-coated BaCe 1-x Gd x O 3-δ @Ce 1-x Gd x O 2-δ core-shell structure composite ceramic.

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