High purity lead bromide and method for its production

Abstract

The application belongs to the field of perovskite materials, and discloses high-purity lead bromide and a production method thereof. The production method of the high-purity lead bromide comprises the following steps: heating and stirring a lead acetate solution, adding a hydrobromic acid solution dropwise into the lead acetate solution, keeping the reaction under the condition of heating and stirring, and then sequentially cooling, aging, solid-liquid separation, washing and drying the obtained solid particles, so that the high-purity lead bromide is obtained. The production method provided by the application controls the reaction system in an acidic environment, which can accelerate the precipitation reaction rate of lead ions and bromine ions, promote the rapid generation of lead bromide crystals, adjust the system dissolution balance in the acidic environment, reduce the solubility product Ksp of lead bromide, reduce the loss of lead ions, ensure that the lead ions are fully converted into lead bromide precipitates, and further improve the yield and purity of the product.

Description

Technical Field

[0001] This invention belongs to the field of perovskite materials and relates to a method for producing lead bromide, specifically a high-purity lead bromide and its production method. Background Technology

[0002] Lead bromide, a compound composed of lead and bromine, has applications in various fields, including the electronics and chemical industries. Its primary use is in photovoltaic devices, particularly in the manufacture of perovskite solar cells. With the continued growth in demand for clean and renewable energy solutions, the lead bromide market is likely to grow in tandem with advancements in solar cell technology and the development of safer, more sustainable materials.

[0003] CN110127755A discloses a method and application for purifying crude lead halide. The method utilizes a hydrothermal process to directly synthesize lead halide from halides (at least one of potassium halide, sodium halide, and ammonium halide) and lead salts (at least one of lead nitrate, lead acetate solution, and lead bromide) under appropriate conditions. Following steps such as filtration, alcohol washing, and drying, the product is finally pulverized and sieved to obtain a high-purity lead halide. However, during the reaction, the reaction system is prone to issues with acid-base regulation, leading to the combination of some lead ions with hydroxide ions in the system. This results in incomplete lead ion precipitation, an unstable crystal growth environment, and difficulty in removing residual impurities, affecting the quality of the final product. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, firstly, the present invention provides a method for producing high-purity lead bromide; secondly, the present invention provides high-purity lead bromide.

[0005] In a first aspect, the present invention provides a method for producing high-purity lead bromide, comprising: heating and stirring a lead acetate solution, adding hydrobromic acid solution dropwise to the lead acetate solution, maintaining the temperature for reaction under heating and stirring, and then sequentially cooling, aging, and solid-liquid separation, washing and drying the obtained solid particles to obtain the high-purity lead bromide.

[0006] Preferably, the concentration of lead acetate solution is 400~600 g / L, and the concentration of hydrobromic acid solution is 100~150 g / L.

[0007] Preferably, the molar ratio of lead ions in the lead acetate solution to bromide ions in the hydrobromic acid solution added to the lead acetate solution is 1:2.01~2.05.

[0008] Preferably, the heating temperature is 55~65℃ and the stirring speed is 300~500r / min.

[0009] Preferably, the hydrobromic acid solution is added dropwise over a period of 25 to 40 minutes.

[0010] Preferably, the heat preservation time is 1 to 1.5 hours.

[0011] Preferably, the cooling rate is 0.6~1℃ / min, and the slurry obtained from the reaction is cooled to 25~35℃.

[0012] Preferably, the aging process is carried out at a temperature of 35~40℃ for 3.5~5 hours.

[0013] Preferably, after aging, the pH value of the resulting slurry is 1.5 to 2.5.

[0014] Preferably, pure water is used to wash the solid particles, and the number of washing cycles is 3 to 5.

[0015] Preferably, the drying temperature is 80~90℃ and the drying time is 8~12h.

[0016] Secondly, the present invention provides a high-purity lead bromide, which is produced by the above-mentioned production method, and the purity of the high-purity lead bromide is >99.0%.

[0017] Preferably, the high-purity lead bromide particles have an elongated shape and an uneven surface.

[0018] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects: (1) The production method provided by the present invention controls the reaction system in an acidic environment, which can accelerate the precipitation reaction rate of lead ions and bromide ions and promote the rapid generation of lead bromide crystals. On the other hand, the acidic environment can adjust the dissolution balance of the system, reduce the solubility product Ksp of lead bromide, reduce the dissolution loss of lead ions, ensure that lead ions are fully converted into lead bromide precipitate, and thus improve the yield and purity of the product.

[0019] (2) Appropriate amount of H in the system + It competes with anions that may bind lead ions (such as acetate ions), reducing the solubility product Ksp of lead bromide, thereby reducing the dissolution loss of lead ions, ensuring that lead ions are fully converted into lead bromide precipitate, and improving product yield and purity.

[0020] (3) The present invention precisely controls the reaction temperature at 55~65℃, and combines the temperature-dependent solubility characteristics of lead bromide with the design of a “slightly soluble and unsaturated” system state to simultaneously improve reaction efficiency and optimize product morphology. Attached Figure Description

[0021] Figure 1 The XRD patterns of lead bromide prepared in Example 1 and Comparative Example 1 are shown. Figure 2 Here is a SEM image of lead bromide prepared in Example 1; Figure 3 SEM image of lead bromide prepared in Comparative Example 1; Figure 4 SEM image of lead bromide prepared in Comparative Example 2; Figure 5 SEM image of lead bromide prepared in Comparative Example 3; Figure 6 SEM image of lead bromide prepared in Comparative Example 4; Figure 7 SEM image of lead bromide prepared in Comparative Example 5; Figure 8 This is a SEM image of lead bromide prepared in Comparative Example 6. Detailed Implementation

[0022] The present invention provides the following specific technical solutions.

[0023] In a first aspect, the present invention provides a method for producing high-purity lead bromide, comprising: heating and stirring a lead acetate solution, adding hydrobromic acid solution dropwise to the lead acetate solution, maintaining the temperature for reaction under heating and stirring, and then sequentially cooling, aging, and solid-liquid separation, washing and drying the obtained solid particles to obtain the high-purity lead bromide.

[0024] Through research, the inventors discovered that the production method provided by this invention controls the reaction system in an acidic environment. On the one hand, this accelerates the precipitation reaction rate of lead ions and bromide ions, promoting the rapid formation of lead bromide crystals. On the other hand, the acidic environment can regulate the dissolution balance of the system, reduce the solubility product Ksp of lead bromide, reduce the dissolution loss of lead ions, ensure that lead ions are fully converted into lead bromide precipitate, and thus improve the yield and purity of the product.

[0025] Preferably, the concentration of lead acetate solution is 400~600 g / L, and the concentration of hydrobromic acid solution is 50~150 g / L.

[0026] Preferably, the molar ratio of lead ions in the lead acetate solution to bromide ions in the hydrobromic acid solution added to the lead acetate solution is 1:2.01~2.05.

[0027] Through research, the inventors discovered that an appropriate excess of bromide ions can drive the reaction to proceed completely in the forward direction, which not only helps to increase the yield of lead bromide but also reduces the waste of raw materials caused by incomplete reaction of lead acetate, while reducing the difficulty of subsequent separation and purification. An excess of hydrobromic acid can maintain the acidic environment of the reaction system, effectively inhibiting possible hydrolysis side reactions of lead bromide and lead ions, and avoiding the formation of impurities such as basic salts, thereby obtaining lead bromide precipitates with higher purity and simpler composition. In addition, this ratio range can avoid excessive consumption of hydrobromic acid while ensuring the reaction effect, thus minimizing raw material costs and rationalizing the waste treatment load.

[0028] Preferably, the heating temperature is 55~65℃ and the stirring speed is 300~500r / min.

[0029] The inventors discovered that preparing lead bromide at room temperature suffers from slow ion diffusion and incomplete reaction due to its low solubility. This invention, however, controls the reaction temperature to 55-65°C, aligning with the characteristic that lead bromide solubility increases systematically with temperature (approximately 0.8 g / L at 20°C, approximately 1.5 g / L at 60°C, and increases sharply above 80°C). This temperature range accelerates the reaction kinetics, preventing excessive product precipitation that could cover the raw materials, ensuring sufficient contact between lead and bromide ions, and significantly improving the conversion rate. Simultaneously, it avoids the morphological defects such as fine crystals and agglomerates formed by rapid product precipitation at room temperature, providing a stable growth environment for crystals. Combined with subsequent controllable cooling and isothermal aging, it guides the directional growth of crystals, resulting in products with uniform particle size and regular morphology. Furthermore, it avoids the cooling-induced agglomeration problem caused by the rapid increase in solubility at high temperatures.

[0030] Preferably, the heat preservation time is 0.5~1.5h.

[0031] Preferably, the cooling rate is 0.6~1℃ / min, and the slurry obtained from the reaction is cooled to 35~40℃.

[0032] Through research, the inventors discovered that by controlling the cooling rate to regulate the growth rhythm of lead bromide crystals, crystallization defects and agglomeration can be avoided, while ensuring the stability of the reaction system, thus producing products with excellent morphology and particle size.

[0033] Preferably, the hydrobromic acid solution is added dropwise over a period of 25 to 40 minutes.

[0034] Through research, the inventors discovered that by controlling the dropping time, the dropping rate can be controlled. A reasonable dropping rate can precisely control the particle size and morphology of lead bromide crystals. At the same time, a suitable dropping rate can prevent impurities in the reaction system from being trapped in the crystal during growth, ensuring the integrity of the crystal structure and thus improving product purity.

[0035] In actual industrial production, multiple feed pipes can be set up, evenly distributed above the reaction tank containing lead acetate. Preferably, the feed rate of a single feed pipe is controlled at 45~55 mL / min, which ensures both production efficiency and the production of products with uniform particle size distribution.

[0036] Preferably, the aging process is carried out at a temperature of 25~35℃ for 3.5~5 hours.

[0037] Through research, the inventors discovered that an aging temperature close to the critical state of "slightly soluble unsaturated" crystals can avoid crystal growth stagnation caused by low temperatures, repair lattice defects through ion migration, and promote a regular morphology. Simultaneously, it can prevent crystal dissolution losses caused by high temperatures, thus maintaining a good yield. Furthermore, a suitable temperature can inhibit the precipitation and agglomeration of new grains, ensuring uniform particle size, accelerating the desorption of impurities from the crystal surface, reducing the risk of residue, and ensuring smooth integration with preceding and following processes, thus guaranteeing system stability and product purity.

[0038] Preferably, after aging, the pH value of the resulting slurry is 1.5 to 2.5.

[0039] The inventors discovered that lead ions readily hydrolyze in a near-neutral environment, forming a colloidal mixture such as basic lead bromide, which compromises the purity and properties of the product. A weakly acidic environment of 1.5–2.5 completely inhibits lead ion hydrolysis, ensuring the formation of a pure white lead bromide precipitate. If the pH is too high (e.g., pH > 5.0), the product will no longer be pure lead bromide, but rather a yellow or grayish-white colloidal mixture containing a large amount of basic salts, resulting in a significant decrease in purity. If the pH is too low (e.g., pH < 1.0), the high hydrogen ion concentration in the system will slightly increase the solubility of lead bromide, causing a slight decrease in product yield. Furthermore, excessive acid will increase the cost of subsequent washing and processing.

[0040] In practical applications, the slurry is allowed to cool naturally to room temperature after aging.

[0041] Preferably, pure water is used to wash the solid particles, and the number of washing cycles is 3 to 5.

[0042] Through research, the inventors discovered that existing technologies use alcohol-based detergents to wash lead bromide. Most alcohols have low boiling points and are highly volatile under working conditions, easily forming explosive mixtures with air. The process requirements are stringent. In order to reduce production risks and save costs, the inventors used pure water to wash solid particles.

[0043] Preferably, the drying temperature is 80~90℃ and the drying time is 8~12h.

[0044] Secondly, the present invention provides a high-purity lead bromide, which is produced by the above-mentioned production method, and the purity of the high-purity lead bromide is >99.0%.

[0045] Preferably, the high-purity lead bromide particles have an elongated shape and an uneven surface.

[0046] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0049] Example 1: A method for producing high-purity lead bromide includes the following steps: Step 1: Weigh 211g of lead acetate and 155mL of hydrobromic acid and use water to prepare solutions of 400g / L and 100g / L, respectively.

[0050] Step 2: Transfer 550 mL of lead acetate solution into the reaction vessel, heat to 55 °C and keep stirring for 30 min at a stirring rate of 500 r / min.

[0051] Step 3: Maintain the temperature and stirring of the lead acetate solution from Step 2, and add hydrobromic acid solution dropwise to the lead acetate solution at a rate of 45 mL / min for 25 min. After the addition is complete, continue stirring at the same temperature for 30 min, then reduce the temperature to 30℃ at a rate of 0.8℃ / min and age for 3.5 h. Then, measure the pH of the reaction system to be 1.90.

[0052] Step 4: Filter the slurry obtained in step 3, wash the solid particles obtained by filtration three times with pure water, dry at 80℃ for 12 hours, grind and sieve to obtain 135.02g of high-purity lead bromide.

[0053] Example 2: A method for producing high-purity lead bromide includes the following steps: Step 1: Weigh 375g of lead acetate and 275mL of hydrobromic acid and use water to prepare solutions of 500g / L and 125g / L, respectively.

[0054] Step 2: Transfer 780 mL of lead acetate solution into the reaction vessel, heat to 60 °C and keep stirring for 30 min at a stirring rate of 400 r / min.

[0055] Step 3: Maintain the temperature and stirring of the lead acetate solution from Step 2, add hydrobromic acid solution dropwise to the lead acetate solution at a rate of 50 mL / min for 31.5 min. After the addition is complete, continue stirring at the same temperature for 60 min, then reduce the temperature to 25℃ at a rate of 1.0℃ / min and age for 4.0 h. The pH of the reaction system is then measured to be 2.08.

[0056] Step 4: Filter the slurry obtained in step 3, wash the solid particles obtained by filtration three times with pure water, dry at 85℃ for 12 hours, grind and sieve to obtain 129.11g of high-purity lead bromide.

[0057] Example 3: A method for producing high-purity lead bromide includes the following steps: Step 1: Weigh 580g of lead acetate and 425mL of hydrobromic acid and use water to prepare solutions of 600g / L and 150g / L, respectively.

[0058] Step 2: Transfer 1030 mL of lead acetate solution into the reaction vessel, heat to 65 °C and keep stirring for 30 min at a stirring rate of 300 r / min.

[0059] Step 3: Maintain the temperature and stirring of the lead acetate solution from Step 2, add hydrobromic acid solution dropwise to the lead acetate solution at a rate of 55 mL / min for 39 min. After the addition is complete, continue stirring at the same temperature for 90 min, then reduce the temperature to 35℃ at a rate of 0.6℃ / min and age for 5.0 h. The pH of the reaction system is then measured to be 2.3.

[0060] Step 4: Filter the slurry obtained in step 3, wash the solid particles obtained by filtration three times with pure water, dry at 90℃ for 8 hours, grind and sieve to obtain 140.49g of high-purity lead bromide.

[0061] Comparative Example 1: A method for producing high-purity lead bromide differs from Example 1 in that, in step 2, 173 mL of lead acetate solution is transferred to a reaction vessel, heated to 30°C, and stirred for 30 min at a stirring rate of 450 r / min.

[0062] All other steps are the same as in Example 1.

[0063] Comparative Example 2: A method for producing high-purity lead bromide differs from Example 1 in that, in step 2, 173 mL of lead acetate solution is transferred to a reaction vessel, heated to 70°C, and stirred for 30 min at a stirring rate of 450 r / min.

[0064] All other steps are the same as in Example 1.

[0065] Comparative Example 3: A method for producing high-purity lead bromide includes the following steps: Step 1: Weigh 211g of lead acetate and 155mL of hydrobromic acid and use water to prepare solutions of 400g / L and 130g / L, respectively.

[0066] Step 2: Transfer 413 mL of lead acetate solution into the reaction vessel, heat to 65 °C and keep stirring for 30 min at a stirring rate of 300 r / min.

[0067] Step 3: Maintain the temperature and stirring of the lead acetate solution from Step 2, add hydrobromic acid solution dropwise to the lead acetate solution at a rate of 45 mL / min for 15 min. After the addition is complete, continue stirring at the same temperature for 30 min, then reduce the temperature to 35℃ at a rate of 0.6℃ / min and age for 5.0 h. Then, measure the pH of the reaction system to be 1.30.

[0068] Step 4: Filter the slurry obtained in step 3, wash the solid particles obtained by filtration three times with pure water, dry at 90℃ for 10 hours, grind and sieve to obtain lead bromide.

[0069] Comparative Example 4: A method for producing high-purity lead bromide includes the following steps: Step 1: Weigh 211g of lead acetate and 155mL of hydrobromic acid and use water to prepare solutions of 650g / L and 60g / L, respectively.

[0070] Step 2: Transfer 325 mL of lead acetate solution into the reaction vessel, heat to 60 °C and keep stirring for 30 min at a stirring rate of 450 r / min.

[0071] Step 3: Maintain the temperature and stirring of the lead acetate solution from Step 2, add hydrobromic acid solution dropwise to the lead acetate solution at a rate of 50 mL / min for 35 min. After the addition is complete, continue stirring at the same temperature for 30 min, then reduce the temperature to 30℃ at a rate of 0.8℃ / min and age for 2 h. Then, measure the pH of the reaction system to be 3.5.

[0072] Step 4: Filter the slurry obtained in step 3, wash the solid particles obtained by filtration three times with pure water, dry at 80℃ for 10 hours, grind and sieve to obtain lead bromide.

[0073] Comparative Example 5: A method for producing high-purity lead bromide differs from Example 1 in that, in step 3, the temperature and stirring of the lead acetate solution in step 2 are maintained, and hydrobromic acid solution is added dropwise to the lead acetate solution at a rate of 45 mL / min for 20 min. After the addition is completed, the solution is kept warm and stirred for another 30 min. Then, the temperature is lowered to 30 °C at a rate of 0.4 °C / min and aged for 8 h. The pH value of the reaction system is then measured to be 1.68.

[0074] Comparative Example 6: A method for producing high-purity lead bromide differs from Example 1 in that, in step 3, the temperature and stirring of the lead acetate solution in step 2 are maintained, and hydrobromic acid solution is added dropwise to the lead acetate solution at a rate of 45 mL / min for 20 min. After the addition is completed, the solution is kept warm and stirred for another 30 min. Then, the temperature is lowered to 30°C at a rate of 1.5°C / min and aged for 1.5 h. The pH of the reaction system is then measured to be 1.72.

[0075] The lead content, particle size, moisture content, and purity of lead bromide prepared in Examples 1-3 and Comparative Examples 1-6 were tested, and the yield was calculated. Specific data are shown in Table 1.

[0076] Table 1. Lead content, particle size, moisture content, purity, and yield of lead bromide obtained in Examples 1-3 and Comparative Examples 1-6. As shown in Table 1, the lead bromide obtained in Examples 1-3 has a purity of up to 99.0%, proving that the production method provided by the present invention can prepare lead bromide products with higher purity.

[0077] Water content is an important characteristic of lead bromide. When preparing perovskite precursor solutions or films, the water in lead bromide will react with organic amine salts (such as methylamine iodine / bromine, MAI / MABr), leading to an imbalance in the ratio of effective reactants and the possible formation of non-target intermediate phases (such as hydrated phases), which seriously disrupts the crystallization process of perovskite and reduces photoelectric conversion efficiency.

[0078] In Examples 1-3, the reaction temperature was precisely controlled between 55 and 65°C, and the moisture content of the products was all below 50 ppm, achieving stable control of extremely low moisture content. Within this temperature range, the metathesis reaction rate of lead acetate and hydrobromic acid was at its optimal level. The crystals grew slowly and uniformly, forming a dense and regular crystal structure, effectively avoiding the encapsulation of the aqueous phase and the adsorption of free water during crystal growth.

[0079] Comparative Example 1 used a low-temperature reaction condition of 30°C, and the product moisture content was 45 ppm, which was slightly higher than that of the Example but still at a low level. Although the low temperature environment slows down the reaction rate, the crystal growth process is relatively slow, the crystal morphology is more regular, the water phase encapsulation is slower, and the residual moisture is mainly surface adsorbed water, without a large amount of encapsulated water that is difficult to remove.

[0080] Comparative Example 2 increased the reaction temperature to 70°C, resulting in a sharp increase in product moisture content to 224 ppm, significantly higher than that of the Examples and Comparative Example 1, highlighting the adverse effects of high temperature on moisture control. High temperatures drastically accelerate the metathesis reaction rate, leading to rapid crystal nucleation and disordered growth, easily forming porous and loose crystal morphologies. During growth, these crystals readily encapsulate a large amount of aqueous phase from the reaction slurry, forming encapsulated water that is difficult to remove through conventional washing and drying. Simultaneously, high temperatures may cause localized overheating, leading to defects such as cracks and pores on the crystal surface, increasing moisture adsorption sites. Furthermore, the intensified changes in ionic strength at high temperatures cause the hydration layer on the crystal surface to thicken, further increasing the possibility of moisture residue. Ultimately, this results in a significant increase in product moisture content, severely impacting product quality.

[0081] Furthermore, by comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that the preferred reaction temperature provided by the present invention can improve the purity of the product, and appropriate heating can prevent the product from precipitating out too quickly and covering the raw materials, ensuring that lead ions and bromide ions are in full contact, thereby improving the conversion rate and product purity.

[0082] Figure 1 The XRD patterns of lead bromide prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 As can be seen from the XRD spectra of Example 1 and Comparative Example 1, at the three strongest peaks, only changing the reaction temperature has a significant effect on the growth of lead bromide crystals. At 60°C, lead bromide tends to grow towards the crystal planes (211), (111), and (031), while at 30°C, lead bromide tends to grow towards the crystal planes (020), (040), and (120). This indicates that stable and suitable thermodynamic and kinetic conditions have a macroscopic regulatory effect on the growth of lead bromide crystals.

[0083] Figure 2 This is a SEM image of lead bromide obtained in Example 1. Figure 2 It can be seen that the lead bromide particles prepared by the preparation process provided by the present invention are mainly long rod-shaped or needle-shaped, mixed with some short columnar particles, with good crystal formation, low agglomeration degree and good dispersion performance.

[0084] Figure 3 The image shows a SEM image of lead bromide prepared in Comparative Example 1. Figure 3 It can be seen that the lead bromide particles prepared in Comparative Example 1 are long rod-shaped or needle-shaped, with amorphous blocky particles mixed in, exhibiting poor crystal formation, high agglomeration, and poor dispersion performance. Compared to... Figure 2 In contrast, the proportion of long rod-shaped or needle-shaped crystals is reduced, and the surface is rougher, with fractures or fragmentation. The particle surface has no obvious crystal face features and exhibits an amorphous or microcrystalline aggregate state.

[0085] Figure 4 The image shows a SEM image of lead bromide prepared in Comparative Example 2. Figure 4 It can be seen that the lead bromide particles obtained in Comparative Example 2 are mainly irregular blocky or spherical aggregates, with no obvious crystal structure, exhibiting irregular blocky and ellipsoidal aggregate morphology. Compared to... Figure 2 In contrast, some particles have defects such as pores and protrusions on their surface, exhibiting a strong aggregated state. The particles are bonded and stacked together, with poor dispersion and no clear independent crystal structure.

[0086] Will Figure 2 Separately and Figure 3 , Figure 4 By comparison, it can be seen that Figure 3 and Figure 4 All of them showed a trend of uncontrolled crystal growth, resulting in crystals failing to grow in a directional manner and instead precipitating in the form of amorphous or microcrystalline aggregates. The products had low morphological uniformity and low dispersibility, which proves that the preparation process provided by the present invention is more stable, can provide a more suitable environment for crystal growth, and the morphology and particle size of the final product are more controllable, which is more in line with the application requirements of high-purity lead bromide.

[0087] Figure 5 The image shows a SEM image of lead bromide prepared in Comparative Example 3. Figure 5 It can be seen that the lead bromide particles prepared in Comparative Example 3 are long rod-shaped crystals, irregular blocks, or aggregates, with poor crystal formation, high degree of agglomeration, and poor dispersion performance. Compared to... Figure 2 In contrast, rod-shaped crystals have rough surfaces and obvious fractures, while blocky particles have irregular crystal faces, wide overall particle size distribution, poor morphological consistency, and severe breakage and agglomeration.

[0088] Figure 6 The image shows a SEM image of lead bromide prepared in Comparative Example 4. Figure 6 It can be seen that the lead bromide particles prepared in Comparative Example 4 exhibit a mixed crystalline aggregate morphology, including a small number of long rod-shaped crystal fragments and a large number of irregular blocky and flocculent aggregates, lacking a uniform crystalline structure overall. Compared to... Figure 2 In contrast, rod-shaped crystals are severely fragmented, with rough surfaces and adherence to blocky particles; blocky aggregates are uneven in size, lack clear crystal faces, and exhibit amorphous or microcrystalline aggregate states; there is significant stacking and adhesion between particles, resulting in extremely poor dispersibility.

[0089] Will Figure 2 Separately and Figure 5 , Figure 6 By comparison, it can be seen that Figure 5 , Figure 6Uncontrolled crystal growth and dispersion conditions led to interrupted crystal growth and massive particle agglomeration, resulting in substandard morphology and particle size uniformity of the product, failing to meet the application requirements of high-purity lead bromide. This further demonstrates that the preparation process provided by this invention is more stable, provides a more suitable environment for crystal growth, and offers greater control over the morphology and particle size of the final product, better meeting the application requirements of high-purity lead bromide.

[0090] Figure 7 The image shows a SEM image of lead bromide prepared in Comparative Example 5. Figure 7 It can be seen that, by Figure 7 It can be seen that the product consists of long rod-shaped / plate-shaped crystals coexisting, with uneven size (20~30μm in length), disordered stacking of crystals and dense surface, with obvious adhesion.

[0091] Figure 8 The image shows a SEM image of lead bromide prepared in Comparative Example 6. Figure 8 It can be seen that the product has a mixed morphology of short rods and irregular blocks, with small crystal size, and some crystal surfaces have holes and fracture defects. The overall packing is loose and has no regular structure.

[0092] Will Figure 2 Separately and Figure 7 , Figure 8 By comparison, it can be seen that Figure 7 , Figure 8 The cooling rate significantly affects the morphology of lead bromide, making it difficult to obtain a single, uniform product. Slow-cooled products contain a mixture of large, cracked particles and normal small particles; fast-cooled products, on the other hand, consist of a large number of fine particles and severe agglomerates. Both result in a wide particle size distribution and inconsistent morphology.

[0093] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing high-purity lead bromide, characterized in that, include: The lead acetate solution was heated and stirred, and hydrobromic acid solution was added dropwise to the lead acetate solution. The reaction was maintained at a constant temperature while being heated and stirred. Then, the solution was cooled, aged, and the solid and liquid were separated in sequence. The obtained solid particles were washed and dried to obtain the high-purity lead bromide.

2. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The concentration of lead acetate solution is 400~600g / L, and the concentration of hydrobromic acid solution is 100~150g / L.

3. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The molar ratio of lead ions in the lead acetate solution to bromide ions in the hydrobromic acid solution added to the lead acetate solution is 1:2.01~2.

05.

4. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The heating temperature is 55~65℃, and the stirring speed is 300~500r / min.

5. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The hydrobromic acid solution is added dropwise over a period of 25 to 40 minutes.

6. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The heat preservation time is 1~1.5h.

7. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The cooling rate is 0.6~1℃ / min, and the slurry obtained from the reaction is cooled to 25~35℃.

8. The method for producing high-purity lead bromide as described in claim 1, characterized in that, The aging process is carried out at a temperature of 35-40℃ for 3.5-5 hours. After aging, the pH value of the resulting slurry is 1.5-2.

5.

9. A high-purity lead bromide, characterized in that, It is produced by the production method described in any one of claims 1 to 8.

10. The high-purity lead bromide as described in claim 9, characterized in that, The purity of the high-purity lead bromide is >99.0%, and the water content of the high-purity lead bromide is less than 50 ppm.

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