A preparation method of lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material

Abstract

This patent belongs to the field of functional ceramics and relates to a method for preparing a multiphase composite ceramic material of lanthanum calcium manganese oxide and metal platinum. The specific steps include using lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate as raw materials, citric acid monohydrate as a chelating agent, and methanol as a solvent, stirring and dissolving, adding ethylene glycol as a dispersant to the mixture, stirring and heating the mixed solution, and drying to obtain a dry gel. The dry gel is ground and calcined to obtain a precursor powder, which is evenly mixed with platinum powder and then pressed and calcined to obtain La 1‑x Ca x MnO3:Pt y Composite ceramic block. La prepared by this method 1‑x Ca x MnO3:Pt y The metal-insulator transition temperature of the composite ceramic is kept close to room temperature, which reduces the resistivity, significantly improves the temperature coefficient of resistance and magnetoresistance, and greatly improves La 1‑x Ca x MnO3:Pt y The possibility of application of composite ceramics in fields such as temperature detection and magnetic storage.

Description

Technical Field

[0001] The invention relates to a preparation method of a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material, belonging to the technical field of functional ceramics. Background Art

[0002] Rare earth manganate La with perovskite structure 1-x Ca x The metal-insulator transition temperature of MnO3 is close to room temperature, and the dramatic resistivity change near the metal-insulator transition temperature leads to a high temperature coefficient of resistance. These unique physical phenomena make this material potentially useful in temperature detection and thermal imaging. Furthermore, the colossal magnetoresistance effect near the metal-insulator transition temperature makes this material potentially useful in magnetic storage and detection. The temperature coefficient of resistance (TCR), metal-insulator transition temperature (TMI), and magnetoresistance (MR) are key parameters that determine whether a material can achieve these applications. The TMI determines the temperature range in which the material can be used; generally, the closer to room temperature, the better. High TCR and MR values ​​improve detection sensitivity and also determine the potential for application. Summary of the Invention

[0003] In order to solve the defects existing in the prior art, the present invention provides a method for preparing a multiphase composite ceramic material of lanthanum calcium manganese oxide and metal platinum. The composite ceramic material of lanthanum calcium manganese oxide and metal platinum is prepared by combining a sol-gel method and a solid-phase method, which greatly improves the possibility of applying rare earth manganate ceramics in fields such as temperature detection and magnetic storage.

[0004] A method for preparing a multiphase composite ceramic material of lanthanum calcium manganese oxide and metal platinum designed to achieve the above purpose comprises the following steps:

[0005] (1) Weigh lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate according to the stoichiometric ratio, add citric acid as a complexing agent, ethylene glycol as a dispersant, and methanol as a solvent, and mix all the mixed raw materials evenly;

[0006] (2) The mixed solution obtained in step (1) is placed in a magnetic stirrer and stirred and mixed uniformly, and heated to perform a foaming reaction until a viscous, transparent, and precipitate-free wet gel state is obtained;

[0007] (3) Place the wet gel obtained in step (2) in an oven and dry for 8-12 hours to obtain a loose, precipitate-free dry gel;

[0008] (4) Grinding the dry gel formed in step (3) into a powder in an agate mortar, and calcining it in a muffle furnace under normal pressure and air atmosphere to obtain a precursor powder;

[0009] (5) Using a solid phase method, the precursor powder obtained in step (4) is mixed with platinum powder in a certain stoichiometric ratio in an agate mortar and fully ground to obtain a mixed powder;

[0010] (6) The mixed powder obtained in step (5) is pressed into blocks in an automatic tablet press, and then finally sintered in a muffle furnace to obtain La 1-x Ca x MnO3: Pt y Composite ceramic blocks.

[0011] Furthermore, the purity of all raw materials in step (1) is not less than 99.9%, and the raw material weighing error is controlled within ±0.05 mg;

[0012] Further optimization, the chemical formula of the Ag-doped nickelate composite ceramic target prepared in step (6) is La 1- x Ca x MnO3: Pt y , where 0< x ≤ 0.4,0.05 ≤ y ≤ 0.2.

[0013] Furthermore, in step (2), when the mixed solution is heated and stirred, the temperature of the magnetic stirrer is set to 70-100° C. and the stirring speed is set to 300 r / min. No precipitate is present after the foaming is completed.

[0014] Furthermore, in step (3), the wet gel is dried under normal pressure and air atmosphere, and the oven temperature is set at 100-180°C.

[0015] Furthermore, the grinding time in step (4) is 0.5-1 h, the calcination temperature is 400-700 °C in an air atmosphere, and the sintering and heat preservation time is 5-10 h.

[0016] Furthermore, the grinding time in step (5) is 1-2 h.

[0017] Furthermore, in step (6), the setting parameters of the automatic tablet press are 3-6 MPa, the duration is about 20-30 min, the sintering temperature is 1400-1550 °C under normal pressure and air atmosphere, and the holding time is 10-16 h.

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

[0019] The present invention utilizes the sol-gel method and the solid phase method to prepare La 1-x Ca x MnO3: Pt yMultiphase composite ceramics maintain the metal-insulator transition temperature close to room temperature, which reduces the resistivity of the material and significantly improves the temperature coefficient of resistance and magnetoresistance, greatly increasing the possibility of applying rare earth manganate composite ceramics in temperature detection and magnetic storage.

[0020] La prepared by the method of the present invention 1-x Ca x MnO3: Pt y The maximum TCR of the composite ceramic is as high as 52.6% / K at 266.3K, and the resistance in an applied magnetic field of 1T is as high as 80.7% at 269K. The method of the present invention has a simple preparation process, a short cycle, and high repeatability, and can be used for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 La obtained in Comparative Example 1 of the present invention 0.67 Ca 0.33 Resistivity-temperature measurement curve of MnO3 ceramic target;

[0022] Figure 2 La obtained in Comparative Example 1 of the present invention 0.67 Ca 0.33 TCR-T measurement curve of MnO3 ceramic target;

[0023] Figure 3 La obtained in Comparative Example 1 of the present invention 0.67 Ca 0.33 MR-T measurement curve of MnO3 ceramic target;

[0024] Figure 4 La obtained in Example 2 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.05 Resistivity-temperature measurement curve of composite ceramic target;

[0025] Figure 5 La obtained in Example 2 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.05 TCR-T measurement curve of composite ceramic target;

[0026] Figure 6 La obtained in Example 2 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.05 MR-T measurement curve of composite ceramic target;

[0027] Figure 7 La obtained in Example 1 of the present invention 0.67 Ca 0.33MnO3: Pt 0.10 Resistivity-temperature measurement curve of composite ceramic target;

[0028] Figure 8 La obtained in Example 1 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.10 TCR-T measurement curve of composite ceramic target;

[0029] Figure 9 La obtained in Example 1 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.10 MR-T measurement curve of composite ceramic target;

[0030] Figure 10 La obtained in Example 3 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.15 Resistivity-temperature measurement curve of composite ceramic target;

[0031] Figure 11 La obtained in Example 3 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.15 TCR-T measurement curve of composite ceramic target;

[0032] Figure 12 La obtained in Example 3 of the present invention 0.67 Ca 0.33 MnO3: Pt 0.15 MR-T measurement curve of composite ceramic target; DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] Example 1

[0035] The preparation method of a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material of this embodiment specifically includes the following steps:

[0036] (1) Lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate with a purity of not less than 99.9% were weighed according to the stoichiometric ratio of the cations in the chemical formula, citric acid monohydrate was used as a complexing agent, and methanol was used as a solvent. The weighed raw materials were stirred on a magnetic stirrer at room temperature to completely dissolve them, and the weighing error was controlled within ±0.5 mg;

[0037] (2) Ethylene glycol is used as a dispersant. After the raw materials in step (1) are completely dissolved, ethylene glycol is added to the mixed solution to fully mix it with the solution, wherein the molar ratio of lanthanum calcium manganese oxide to ethylene glycol is 1:2;

[0038] (3) After the mixed solution in step (2) is fully mixed, the solution is transferred to a magnetic heating stirrer at 88°C for heating and stirring. When the solution turns dark yellow and foaming is observed, the mixed solution is transferred to a constant temperature oven at 140°C for full foaming and drying for 12 h to obtain a dry gel.

[0039] (4) The dry gel in step (3) was placed in an agate mortar and ground thoroughly for 0.7 h. The ground powder was placed in a muffle furnace and calcined at 500 °C for 8 h to remove organic matter and nitrate ions in the gel to obtain a black precursor powder;

[0040] (5) mixing the lanthanum calcium manganese oxide precursor powder obtained in step (4) with platinum powder in a certain stoichiometric ratio in an agate mortar and grinding for 1.5 h to obtain a mixed precursor powder;

[0041] (6) The mixed precursor powder obtained in step (5) was pressed into a block in an automatic tablet press at a pressing pressure of 5 MPa for 20 min, and then placed in a muffle furnace and sintered at 1450 ° C for 12 h to obtain La 1-x Ca x MnO3: Pt y Composite ceramic block of composite ceramic, wherein x = 0.33, y=0.05.

[0042] The lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic La obtained in Example 1 0.67 Ca 0.33 MnO3: Pt 0.05 , see Figure 4 、 5 , 6, at 265.2 K, the TCR is 51.2% / K, and the maximum MR is 78.3% at 1 T magnetic field.

[0043] Comparative Example 1

[0044] The preparation method of a lanthanum calcium manganese oxide ceramic material of this embodiment specifically includes the following steps:

[0045] (1) Preparation of La by combining sol-gel method and solid phase method 0.67 Ca 0.33 For MnO3 ceramic targets, lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate with a purity of not less than 99.9% are weighed according to the stoichiometric ratio of cations in the chemical formula. Citric acid monohydrate is used as a complexing agent and methanol is used as a solvent. The weighed raw materials are stirred on a magnetic stirrer at room temperature to completely dissolve them. The weighing error is controlled within ±0.5 mg.

[0046] (2) Ethylene glycol is used as a dispersant. After the raw materials in step (1) are completely dissolved, ethylene glycol is added to the mixed solution to fully mix it with the solution, wherein the molar ratio of lanthanum calcium manganese oxide to ethylene glycol is 1:2;

[0047] (3) After the mixed solution in step (2) is fully mixed, the solution is transferred to a magnetic heating stirrer at 88°C for heating and stirring. When the solution turns dark yellow and foaming is observed, the mixed solution is transferred to a constant temperature oven at 140°C for full foaming and drying for 12 h to obtain a dry gel.

[0048] (4) The dry gel in step (3) was placed in an agate mortar and ground thoroughly for 0.7 h. The ground powder was placed in a muffle furnace and calcined at 500 °C for 8 h to remove organic matter and nitrate ions in the gel to obtain a black precursor powder;

[0049] (5) The mixed precursor powder obtained in step (4) was pressed into a block in an automatic tablet press at a pressing pressure of 5 MPa for 20 min, and then placed in a muffle furnace and sintered at 1450 °C for 12 h to obtain La 0.67 Ca 0.33 MnO3 polycrystalline ceramics.

[0050] The La obtained in this comparative example 1 0.67 Ca 0.33 MnO3, see Figure 1 、 2 , 3. At 259.4 K, the TCR is 40.1% / K, and the maximum MR is 60.3% at 1 T magnetic field.

[0051] Example 2

[0052] In this embodiment, La 1-x Ca x MnO3: Pt y of x = 0.33, y = 0.1, and other step parameters are the same as those in Example 1.

[0053] The lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic La obtained in Example 2 0.67 Ca0.33 MnO3: Pt 0.1 ,See Figure 7 、 8 , 9, we can see that at 266.3 K, the TCR is 52.6% / K, and the maximum MR is 80.7% at 1 T magnetic field.

[0054] Example 3

[0055] In this embodiment, La 1-x Ca x MnO3: Pt y of x = 0.33, y = 0.15, and other step parameters are the same as those in Example 1.

[0056] The La obtained in Example 3 0.67 Ca 0.33 MnO3: Pt 0.15 , see Figure 4 、 5 , 6, at 266.4 K, the TCR is 52.8% / K, and the maximum MR is 80.0% at 1 T magnetic field.

[0057] Example 4

[0058] The preparation method of a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material of this embodiment specifically includes the following steps:

[0059] (1) Lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate with a purity of not less than 99.9% were weighed according to the stoichiometric ratio of the cations in the chemical formula, citric acid monohydrate was used as a complexing agent, and methanol was used as a solvent. The weighed raw materials were stirred on a magnetic stirrer at room temperature to completely dissolve them, and the weighing error was controlled within ±0.5 mg;

[0060] (2) Ethylene glycol is used as a dispersant. After the raw materials in step (1) are completely dissolved, ethylene glycol is added to the mixed solution to fully mix it with the solution, wherein the molar ratio of lanthanum calcium manganese oxide to ethylene glycol is 1:2;

[0061] (3) After the mixed solution in step (2) is fully mixed, the solution is transferred to a magnetic heating stirrer at 70°C for heating and stirring. When the solution turns dark yellow and foaming is observed, the mixed solution is transferred to a constant temperature oven at 100°C for full foaming and drying for 14 hours to obtain a dry gel.

[0062] (4) The dry gel in step (3) was placed in an agate mortar and ground thoroughly for 0.5 h. The ground powder was placed in a muffle furnace and calcined at 400 °C for 10 h to remove organic matter and nitrate ions in the gel to obtain a black precursor powder;

[0063] (5) mixing the lanthanum calcium manganese oxide precursor powder obtained in step (4) with platinum powder in a certain stoichiometric ratio in an agate mortar and grinding for 1 h to obtain a mixed precursor powder;

[0064] (6) The mixed precursor powder obtained in step (5) was pressed into a block in an automatic tablet press at a pressure of 3 MPa for 20 min and then placed in a muffle furnace for sintering at 1400 °C for 10 h. x = 0.33, y = 0.05 to obtain composite ceramic La 0.67 Ca 0.33 MnO3: Pt 0.05 Composite ceramic blocks.

[0065] Example 5

[0066] The method for preparing an Ag-doped nickelate ceramic for room temperature high-sensitivity infrared detection of this embodiment specifically includes the following steps:

[0067] (1) Lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate with a purity of not less than 99.9% were weighed according to the stoichiometric ratio of the cations in the chemical formula, citric acid monohydrate was used as a complexing agent, and methanol was used as a solvent. The weighed raw materials were stirred on a magnetic stirrer at room temperature to completely dissolve them, and the weighing error was controlled within ±0.5 mg;

[0068] (2) Ethylene glycol is used as a dispersant. After the raw materials in step (1) are completely dissolved, ethylene glycol is added to the mixed solution to fully mix it with the solution, wherein the molar ratio of lanthanum calcium manganese oxide to ethylene glycol is 1:2;

[0069] (3) After the mixed solution in step (2) is fully mixed, the solution is transferred to a magnetic heating stirrer at 100°C for heating and stirring. When the solution turns dark yellow and foaming is observed, the mixed solution is transferred to a constant temperature oven at 180°C for full foaming and drying for 7 hours to obtain a dry gel.

[0070] (4) The dry gel in step (3) was placed in an agate mortar and ground thoroughly for 1 h. The ground powder was placed in a muffle furnace and calcined at 700 °C for 5 h to remove organic matter and nitrate ions in the gel to obtain a black precursor powder;

[0071] (5) mixing the lanthanum calcium manganese oxide precursor powder obtained in step (4) with platinum powder in a certain stoichiometric ratio in an agate mortar and grinding for 2 h to obtain a mixed precursor powder;

[0072] (6) The mixed precursor powder obtained in step (5) was pressed into a block in an automatic tablet press at a pressure of 6 MPa for 30 min and then placed in a muffle furnace and sintered at 1550 °C for 16 h. La 0.6 Ca 0.4 MnO3:Pt 0.2 Composite ceramic blocks of composite ceramics.

[0073] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a multiphase composite ceramic material of lanthanum calcium manganese oxide and metal platinum, characterized in that: The steps include: (1) Weighing high-purity lanthanum nitrate hexahydrate, calcium nitrate tetrahydrate, and manganese nitrate tetrahydrate according to the stoichiometric ratio of the cations in the chemical formula, using citric acid monohydrate as a complexing agent and methanol as a solvent, and stirring the weighed raw materials on a magnetic stirrer at room temperature to completely dissolve them; (2) Ethylene glycol is used as a dispersant. After the raw materials in step (1) are completely dissolved, ethylene glycol is added to the mixed solution to fully mix it with the solution; (3) After the mixed solution in step (2) is fully mixed, the solution is transferred to a magnetic heating stirrer for heating and stirring. When the solution turns dark yellow and foaming is observed, the mixed solution is transferred to a constant temperature oven for full foaming and drying to obtain a dry gel; (4) The dry gel prepared in step (3) was placed in an agate mortar and ground thoroughly. The ground powder was calcined in a muffle furnace to remove organic matter and nitrate ions in the gel to obtain a black precursor powder; (5) mixing the precursor powder obtained in step (4) with platinum powder in a certain stoichiometric ratio in an agate mortar and grinding them thoroughly to obtain a mixed precursor powder; (6) The mixed precursor powder obtained in step (5) is pressed into a block in an automatic tablet press, and then placed in a muffle furnace for high-temperature sintering to obtain La 1-x Ca x MnO3: Pt y Composite ceramic blocks, wherein x =0.33,0.05≤ y ≤0.2, the chemical formula of the composite ceramic is La 0.67 Ca 0.33 MnO3: Pt y .

2. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: The purity of all raw materials in step (1) is not less than 99.9%, and the weighing error is controlled within ±0.5 mg.

3. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: The molar ratio of lanthanum calcium manganese oxide to ethylene glycol in step (2) is 1:

2.

4. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: In step (3), the mixed solution is heated to a reaction temperature of 70-100°C and stirred at a speed of 300 r / min.

5. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: In step (3), the oven temperature is set to 100-180 °C, and the drying time is 7-14 h under normal pressure and air atmosphere.

6. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: The grinding time of step (4) is 0.5-1.0 h, the calcination temperature is 400-700 °C in an air atmosphere, and the sintering holding time is 5-10 h.

7. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: The grinding time in step (5) is 1-2 hours.

8. The method for preparing a lanthanum calcium manganese oxide and metal platinum multiphase composite ceramic material according to claim 1, characterized in that: In step (6), the setting parameters of the automatic tablet press are 3-6 MPa, the pressing time is 20-30 min, the sintering temperature is 1400-1550 °C under normal pressure and air atmosphere, and the holding time is 10-16 h.

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