Method for preparing yttrium aluminum garnet powder at low temperature and low pressure

Abstract

The invention provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, and relates to the field of materials. The method comprises the following steps: mixing YOCl, AlCl36H2O, water and ethanol to obtain a mixture, then adding hydrochloric acid to adjust the pH value of a system to strong acidity, and then carrying out a heating reaction under a normal pressure condition; after the reaction is finished, adding an ammonium bicarbonate aqueous solution to obtain a gelatinous precipitate; drying and grinding the gelatinous precipitate to obtain a precursor; and roasting the precursor to obtain yttrium aluminum garnet powder. The yttrium oxychloride is adopted as the yttrium source to replace traditional yttrium oxide, and aluminum chloride hexahydrate is combined as the aluminum source, so that the activation energy of the hydrothermal reaction is reduced. And by introducing hydrochloric acid, the dissociation of YOCl can be effectively promoted, the dissolution of Y < 3 + > ions is enhanced, and the reaction is promoted. The reason of adding ethanol is to hinder the generation of impurity phases. Through the means, the conditions required by the reaction can be obviously reduced, and the high-purity yttrium aluminum garnet powder can be prepared under the mild condition.

Description

Technical Field

[0001] The present application relates to the field of materials, and in particular to a method for preparing yttrium aluminum garnet powder at low temperature and low pressure. Background Art

[0002] Yttrium aluminum garnet (Y 3 Al 5 O 12 The purity of YAG (YAG) powder is the core factor that determines its functional properties and engineering application performance. High-purity YAG (phase purity > 99%) can significantly improve the mechanical strength and high-temperature phase stability of the material, thereby meeting the stringent requirements of laser crystals, fluorescent matrices and advanced thermal barrier coatings for the intrinsic performance of the material. However, the presence of trace impurities (such as YAP, YAM) will introduce lattice defects and interface scattering centers, resulting in decreased phonon transmission efficiency, increased thermal expansion mismatch and the risk of phase transition under high temperature environments, which seriously restricts the service life and reliability of the material. In addition, impurity elements (such as Fe and Si) may cause fluorescence quenching or optical scattering, further limiting its application in the field of optoelectronics. Therefore, the development of efficient and high-purity YAG synthesis methods, the suppression of impurity generation and the realization of atomic-scale component uniformity have become key research directions for breaking through the bottleneck of material performance. The main preparation methods currently include: solid-phase reaction method, sol-gel method, co-precipitation method, hydrothermal method, etc.

[0003] The sintering ability of solid-phase reaction powder is poor, and it is impossible to prepare large-sized and highly transparent YAG ceramic materials. This is because the solid-phase reaction requires a higher synthesis temperature, which will result in larger powder particles, more serious agglomeration, and uneven product composition and structure. In addition, the solid-phase method usually requires a long mixing time, which may cause serious powder contamination and affect the uniformity of the microstructure. This makes it challenging to obtain high density during the sintering process of the green body, which will affect the light transmittance of YAG ceramics. Due to the high cost of organic raw materials used in the sol-gel method, the high difficulty of operation increases the difficulty of the process. The crystallinity of the prepared product is relatively low, because the precursor will form hard agglomerates of powder particles during heat treatment, which makes the final prepared powder poor in dispersibility and unsatisfactory in sintering activity. The precipitation process of the coprecipitation method is relatively complicated, and it is necessary to control multiple factors such as the amount of precipitant added, precipitation temperature, precipitation time, etc., otherwise it is easy to cause incomplete precipitation or impure products. The products of the coprecipitation method are easy to agglomerate. Due to the strong interaction between particles during the precipitation process, it is easy to cause product agglomeration, thereby affecting the performance of the product. The precipitation method is more expensive: a large amount of precipitant and solvent is required, and the precipitation process takes a long time, so the cost is higher.

[0004] The traditional hydrothermal method has many advantages in the field of YAG synthesis, but it faces multiple challenges: (1) High pressure dependence: the reaction needs to maintain a pressure of >10 MPa to ensure the supercritical state of the solvent, resulting in high equipment costs and complex maintenance; (2) Reaction efficiency limitation: Al2O3 is not effective at high temperatures (>220 °C). 3+ It is easy to hydrolyze to form AlOOH impurity phase, and the reaction time needs to be extended to 12~24 h to improve the conversion rate, which increases energy consumption. Summary of the invention

[0005] The purpose of this application is to provide a method for preparing yttrium aluminum garnet powder at low temperature and low pressure to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions: A method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising: YOCl、AlCl 3 •6H 2 O, water and ethanol are mixed to obtain a mixture, and then hydrochloric acid is added to adjust the pH of the system to a strong acid, and then heating reaction is carried out under normal pressure; after the reaction is completed, an ammonium bicarbonate aqueous solution is added to obtain a gel precipitate; Drying and grinding the gelatinous precipitate to obtain a precursor; The precursor is calcined to obtain the yttrium aluminum garnet powder.

[0007] Preferably, the YOCl and the AlCl 3 •6H 2 The amount of O is measured according to the stoichiometric ratio of n(Y):n(Al)=3:5.

[0008] Preferably, the volume ratio of the water to the ethanol is 1:0.8-1.2.

[0009] Preferably, the liquid-to-solid ratio of the mixture is 6.0-6.5 ml / g.

[0010] Preferably, the strongly acidic pH is -0.04 to 0.5.

[0011] Preferably, the aqueous ammonium bicarbonate solution is added until the pH of the system is 6-9.

[0012] Preferably, the reaction temperature is 185-195°C and the reaction time is 6.5-7.5h.

[0013] Preferably, the reaction is carried out under stirring at a stirring rate of 400-600 r / min.

[0014] Preferably, the calcination temperature is 1000-1200° C. and the calcination time is 2-3 hours.

[0015] Preferably, the YOCl is prepared by calcining YCl 3 •6H 2 O was prepared.

[0016] Compared with the prior art, the beneficial effects of this application include: The present application provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, using yttrium oxychloride (YOCl) as the yttrium source to replace the traditional yttrium oxide (Y 2 O 3 ), combined with aluminum chloride hexahydrate (AlCl 3 •6H 2 O) as an aluminum source to reduce the activation energy of the hydrothermal reaction. Experimental studies have shown that when HCl is not introduced, undissociated YOCl solid residues exist in the reaction system, while the introduction of hydrochloric acid can effectively promote the dissociation of YOCl. HCl can enhance the activation energy of the hydrothermal reaction by reducing the pH value of the solution. 3+ The dissolution of ions promotes the reaction. Therefore, through these means, the conditions required for the reaction can be significantly reduced, and the material preparation under mild conditions can be achieved. The reason for adding ethanol is to prevent the formation of impurity phases. The mechanism is: ethanol molecules react with [Al(OH) 6 ] 3- The hydroxyl complex can effectively inhibit the formation of boehmite (γ-AlOOH) intermediate phase with the participation of OH⁻ groups. 3+ With Al 3+ The ions tend to deposit preferentially on the surface of their respective nuclei through a spontaneous nucleation process and undergo grain growth, making Y 3+ or Al 3+ The addition of ethanol will hinder the migration speed of ions, thereby reducing the Y 3+ 、Al 3+ The ability to gather together alone makes Y 3+ and Al 3+ Co-precipitation is carried out according to the stoichiometric ratio of the target high-purity product. In addition, the addition of organic solvent will reduce the oxygen bond force of the original water system and reduce the generation of agglomeration.

[0017] Based on the above reasons, the method for preparing yttrium aluminum garnet powder at low temperature and low pressure provided in this application not only reduces the equipment cost but also has no harmful solvent pollution in the whole process, meets the requirements of green chemistry, and the purity of the obtained YAG powder reaches more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0019] Figure 1 A schematic diagram of the process flow of the method for preparing yttrium aluminum garnet powder at low temperature and low pressure provided in this application; Figure 2 The XRD spectra of the powders obtained in the examples and comparative examples are shown in FIG. DETAILED DESCRIPTION

[0020] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows: A method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising: YOCl、AlCl 3 •6H 2 O, water and ethanol are mixed to obtain a mixture, and then hydrochloric acid is added to adjust the pH of the system to a strong acid, and then heating reaction is carried out under normal pressure; after the reaction is completed, an ammonium bicarbonate aqueous solution is added to obtain a gel precipitate; Drying and grinding the gelatinous precipitate to obtain a precursor; The precursor is calcined to obtain the yttrium aluminum garnet powder.

[0021] In an optional embodiment, the YOCl and the AlCl 3 •6H 2 The amount of O is measured according to the stoichiometric ratio of n(Y):n(Al)=3:5.

[0022] Since the target product is high-purity yttrium aluminum garnet powder, the raw materials need to be measured strictly according to the above-mentioned stoichiometric ratio.

[0023] In an optional embodiment, the volume ratio of the water to the ethanol is 1:0.8-1.2.

[0024] When the volume ratio of ethanol to water deviated from the range of 1:1±0.2, impurities were detected in the product.

[0025] Optionally, the volume ratio of the water to the ethanol can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2 or any value between 1:0.8-1.2.

[0026] In an optional embodiment, the liquid-to-solid ratio of the mixture is 6.0-6.5 ml / g.

[0027] Optionally, the liquid-to-solid ratio of the mixture can be 6.0 ml / g, 6.1 ml / g, 6.2 ml / g, 6.3 ml / g, 6.4 ml / g, 6.5 ml / g or any value between 6.0-6.5 ml / g.

[0028] In an optional embodiment, the strongly acidic pH is -0.04 to 0.5.

[0029] Optionally, the strongly acidic pH may be -0.04, 0, 0.1, 0.5 or any value between -0.04 and 0.5.

[0030] Hydrochloric acid generally uses concentrated hydrochloric acid with a concentration greater than or equal to 35wt% to achieve the above-mentioned strong acidic environment.

[0031] In an optional embodiment, the aqueous ammonium bicarbonate solution is added until the pH of the system is 6-9.

[0032] Optionally, the aqueous ammonium bicarbonate solution is added until the pH of the system is 6, 7, 8, 9 or any value between 6 and 9.

[0033] In an optional embodiment, the reaction temperature is 185-195° C. and the reaction time is 6.5-7.5 h.

[0034] Optionally, the reaction temperature may be 185°C, 190°C, 195°C or any value between 185-195°C, and the reaction time may be 6.5h, 7h, 7.5h or any value between 6.5-7.5h.

[0035] In an optional embodiment, the reaction is carried out under stirring at a stirring rate of 400-600 r / min.

[0036] Optionally, the stirring rate may be 400 r / min, 500 r / min, 600 r / min or any value between 400-600 r / min.

[0037] In an optional embodiment, the calcination temperature is 1000-1200° C. and the calcination time is 2-3 hours.

[0038] High-purity products can be obtained by calcining at relatively low temperatures and in a short time.

[0039] Optionally, the calcination temperature may be 1000° C., 1100° C., 1200° C. or any value between 1000-1200° C., and the calcination time may be 2 h, 2.5 h, 3 h or any value between 2-3 h.

[0040] In an optional embodiment, the YOCl is prepared by calcining YCl3 •6H 2 O was prepared.

[0041] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0042] Example 1 like Figure 1 As shown, this embodiment provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising the following steps: According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was phase analyzed by X-ray diffraction, and the results are as follows Figure 2 The diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and no obvious impurity phase (such as YAM or YAP) is detected. Through component analysis, the purity of YAG reaches 99.7%, indicating that this method can achieve high-purity phase synthesis of YAG.

[0043] Example 2 This embodiment provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising the following steps: According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 188℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 The diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and no obvious impurity phase (such as YAM or YAP) is detected, which is basically consistent with the XRD pattern of Example 1. Through component analysis, the purity of YAG reaches 99.1%.

[0044] Example 3 This embodiment provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising the following steps: According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then introduce concentrated hydrochloric acid (36wt%) to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 192℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 The diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and no obvious impurity phase (such as YAM or YAP) is detected, which is basically consistent with the XRD pattern of Example 1. Through component analysis, the purity of YAG reaches 99.4%.

[0045] Example 4 This embodiment provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising the following steps: According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1.2), the liquid-solid ratio is 6.2ml / g, and then concentrated hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 The diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and no obvious impurity phase (such as YAM or YAP) is detected, which is basically consistent with the XRD pattern of Example 1. Through component analysis, the purity of YAG reaches 99.3%.

[0046] Example 5 This embodiment provides a method for preparing yttrium aluminum garnet powder at low temperature and low pressure, comprising the following steps: According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:0.8), the liquid-solid ratio is 6.2ml / g, and then concentrated hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was phase analyzed by X-ray diffraction, and the results are as follows Figure 2The diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and no obvious impurity phase (such as YAM or YAP) is detected, which is basically consistent with the XRD pattern of Example 1. Through component analysis, the purity of YAG reaches 99.1%.

[0047] In Examples 2 to 5, the YAG powder still has the problem of impurity phase (YAM / YAP), but its phase purity can meet the basic requirement of higher purity (purity>97%). The optimized process of Example 1 is the best process, which provides a scalable synthesis path for the industrial production of YAG powder (yield>99%).

[0048] Comparative Example 1 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 6 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and YAP and YAM impurities are detected at the same time. Through component analysis, the purity of YAG is 96.6%, YAP accounts for 1.9%, and YAM accounts for 1.5%.

[0049] In this comparative example, shortening the reaction time to 6 h resulted in a significant decrease in phase purity, and the shorter constant temperature time was not sufficient to achieve complete reaction.

[0050] Comparative Example 2 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 8 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and some YAM and YAP impurities are detected. Through component analysis, the purity of YAG is 91.2%, YAM accounts for 5.3%, and YAP accounts for 3.5%.

[0051] In this comparative example, the increase of reaction time to 8 h resulted in a significant decrease in phase purity. The longer the constant temperature time, the more impurities there were in the reaction system, which may be due to the initiation of side reactions.

[0052] Comparative Example 3 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, no anhydrous ethanol solution is added, the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190 ℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000 ℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 After calcination, the powder has more impurities, and some YAG phases, as well as YAM, YAP, and Al 2 O 3 Mixed phase. Through composition analysis, the YAG phase accounts for 90.5%, YAM accounts for 4.1%, and YAP accounts for 5.4%.

[0053] In this comparative example, no ethanol was added, resulting in the formation of an impurity phase.

[0054] Comparative Example 4 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 2:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and some YAM and YAP impurities are detected. Through component analysis, the purity of YAG is 89.5%, YAM accounts for 7.7%, and YAP accounts for 2.8%.

[0055] The amount of ethanol used in this comparative example is too low, which also leads to the generation of impurity phase.

[0056] Comparative Example 5 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:2), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and some YAM and YAP impurities are detected. Through component analysis, the YAG phase accounts for 92.6%, YAM accounts for 2.9%, and YAP accounts for 4.5%.

[0057] The amount of ethanol used in this comparative example is too high, which also leads to the generation of impurity phase.

[0058] It should be noted that experiments have shown that other alcohol compounds, such as isopropanol, cannot be used to replace ethanol. In the isopropanol system, the metal aluminum / yttrium particles need to undergo a high-temperature reflux (85°C) hydrolysis condensation reaction with isopropanol to generate an isopropoxide precursor. This process is limited by the low diffusion rate caused by the large molecular weight of isopropanol, and a precipitant (NH 4 HCO 3 ) The gelation process of YAG ceramics has the disadvantages of long process and poor controllability of the intermediate phase. In addition, the low boiling point of ethanol (78.4°C) is more conducive to the complete removal of solvent molecules in the early stage of calcination than isopropanol (82.6°C). Residual isopropanol will generate organic carbon fragments, which will affect the densification sintering performance of YAG ceramics.

[0059] Comparative Example 6 According to the stoichiometric ratio of n(Y):n(Al)=3:4.5, accurately weigh YOCl and AlCl 3 •6H 2O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was phase analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. After calcination, the powder has more impurities, and some YAG phases, as well as YAM, YAP, and Y2O3 impurities are detected. The increase in aluminum will cause the excess aluminum to form aluminum oxide impurities with air oxygen. Through component analysis, the YAG phase accounts for 77.4%, YAM accounts for 8.4%, YAP accounts for 4%, and Y 2 O 3 The proportion is 10.2%.

[0060] Comparative Example 7 According to the stoichiometric ratio of n(Y):n(Al)=3:6, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 190℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was phase analyzed by X-ray diffraction, and the results are as follows Figure 2 After calcination, the powder has more impurities, and some YAG phases, as well as YAM, YAP, and Al 2 O 3The increase of aluminum will cause the excess aluminum to form aluminum oxide impurity phase with air oxygen. Through composition analysis, YAG phase accounts for 68.6%, YAM accounts for 10.6%, YAP accounts for 7.4%, and Al 2 O 3 The proportion is 13.4%.

[0061] In Comparative Examples 6 and 7, the raw materials YOCl and AlCl 3 •6H 2 An inappropriate proportion of O also leads to the formation of impurity phases.

[0062] Comparative Example 8 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2 O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 200℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and some YAM and YAP impurities are detected. Through component analysis, the YAG phase accounts for 94.5%, YAM accounts for 3.6%, and YAP accounts for 1.9%.

[0063] In this comparative example, the hydrothermal reaction temperature is too high, which also leads to the generation of impurity phase.

[0064] Comparative Example 9 According to the stoichiometric ratio of n(Y):n(Al)=3:5, accurately weigh YOCl and AlCl 3 •6H 2O reagent, mix them and put them into a polytetrafluoroethylene liner, add a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1), the liquid-solid ratio is 6.2ml / g, and then hydrochloric acid (36wt%) is introduced to adjust the pH value of the system to the range of -0.04~0.5 to prepare the reactants for the hydrothermal reaction. The polytetrafluoroethylene container containing the reactants is placed in a high-temperature and high-pressure reactor, the reaction temperature is set to 180℃, and the constant temperature reaction is carried out for 7 hours. During the process, the magnetic stirring rate in the reactor is kept at 500 r / min. When the reaction is completed, the hydrothermal product is cooled to room temperature and 2 mol / L ammonium bicarbonate is added dropwise to adjust the pH of the system to 7.5 to form a gel. Then it is placed in a drying oven for drying and grinding to obtain a precursor powder. The precursor is calcined in a muffle furnace at 1000℃ for 2 hours to obtain YAG powder. The product was phase analyzed by X-ray diffraction, and the results are as follows Figure 2 As shown. The main diffraction peaks of the calcined powder are highly consistent with the YAG standard card, and some YAM and YAP impurities are detected. Through component analysis, the YAG phase accounts for 94.3%, YAM accounts for 3.3%, and YAP accounts for 2.4%.

[0065] In this comparative example, the hydrothermal reaction temperature is too low, which also leads to the generation of impurity phases.

[0066] The method provided in this application has the following advantages: 1. New raw material system and pretreatment process; using yttrium oxychloride (YOCl) as the yttrium source to replace traditional yttrium oxide (Y 2 O 3 ), combined with aluminum chloride hexahydrate (AlCl 3 •6H 2 O) as an aluminum source to reduce the activation energy of the hydrothermal reaction, which is an innovation in the raw materials of the new method. This raw material system avoids the problems of low oxide diffusion rate and harsh hydrothermal conditions in the traditional solid phase method, and does not require the introduction of high-cost organic precursors.

[0067] 2. The hydrothermal reaction conditions are mild; the aluminum and yttrium ions are uniformly complexed under low pressure. The alcohol-water mixed solvent system effectively inhibits side reactions, and the addition of HCl adjusts the pH value of the solution, promotes the uniform formation of the precursor gel, and provides a highly active precursor for subsequent low-temperature calcination.

[0068] 3. Low-temperature calcination and crystal phase control technology: The precursor can be converted into pure phase YAG after a short calcination at 1000-1200℃, which greatly reduces energy consumption compared with the traditional solid phase method (above 1400℃). By controlling the calcination temperature and holding time, the abnormal growth of grains is suppressed, and low-agglomeration YAG powder is produced.

[0069] 4. Green and environmentally friendly with good adaptability to industrialization; the whole process adopts hydrothermal method combined with low-temperature calcination to avoid the high energy consumption of high-temperature solid-phase reaction and the pollution problem of organic solvents in sol-gel method, which meets the requirements of green chemistry and sustainable development.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing yttrium aluminum garnet powder at low temperature and low pressure, characterized in that: include: YOCl, AlCl3•6H2O, water and ethanol are mixed to obtain a mixture, and then hydrochloric acid is added to adjust the pH of the system to a strong acid, and then heating reaction is carried out under normal pressure; after the reaction is completed, an ammonium bicarbonate aqueous solution is added to obtain a gel precipitate; Drying and grinding the gelatinous precipitate to obtain a precursor; The precursor is calcined to obtain the yttrium aluminum garnet powder.

2. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The amounts of the YOCl and the AlCl3•6H2O are measured according to a stoichiometric ratio of n(Y):n(Al)=3:

5.

3. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The volume ratio of the water to the ethanol is 1:0.8-1.

2.

4. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The liquid-to-solid ratio of the mixture is 6.0-6.5 ml / g.

5. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The strongly acidic pH is -0.04 to 0.

5.

6. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The ammonium bicarbonate aqueous solution is added until the pH of the system is 6-9.

7. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The reaction temperature is 185-195°C and the reaction time is 6.5-7.5h.

8. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The reaction is carried out under stirring at a rate of 400-600 r / min.

9. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to claim 1, characterized in that: The calcination temperature is 1000-1200° C. and the calcination time is 2-3 hours.

10. The method for preparing yttrium aluminum garnet powder at low temperature and low pressure according to any one of claims 1 to 9, characterized in that: The YOCl is prepared by calcining YCl3•6H2O.

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