What Is Barium Phosphate?
Barium phosphate is an inorganic compound with the chemical formula Ba3(PO4)2. It is a white, odorless solid that is insoluble in water.
Properties of Barium Phosphate
- Crystal structure: It crystallizes in the orthorhombic system
- Thermal properties: It exhibits a diffuse phase transition behavior
- Dielectric and conductivity properties: It shows temperature and frequency-dependent dielectric constant, dielectric loss, and AC conductivity
- Morphology: Nanostructured one can form irregular flakes or particles in the range of 20-100 nm
Preparation of Barium Phosphate
Precipitation Methods
- Co-precipitation: The most common method, involving mixing aqueous solutions of barium and phosphate sources (e.g., barium chloride and sodium phosphate) to precipitate it. Key factors include concentration, pH, temperature, and mixing rate.
- Single-source method: An improved co-precipitation method using only Na4Fe(CN)6 as the iron source, which decomposes to form Fe2+ and Fe3+ that react with remaining Fe(CN)64- to precipitate it.
Hydrothermal Synthesis
- Involves high temperature and pressure to dissolve and recrystallize insoluble compounds.
- Produces barium phosphates with good uniformity, dispersibility, and crystallinity.
- Allows precise control over composition and morphology.
Solid-state Reactions
Ball milling: Mechanochemical synthesis by grinding barium sulfate and ammonium dihydrogen phosphate or phosphoric acid at high temperatures (e.g., 500°C).
Novel Approaches
- Microreactor method: Continuous synthesis in microreactors for better control over particle size and morphology.
- Biosynthesis: Green synthesis using bacteria to precipitate barium phosphates with controlled sizes and shapes.
- Conversion of borate glasses: Formation of barium phosphates by converting barium borate glasses in dilute phosphate solutions at near room temperature
Applications of Barium Phosphate
Catalytic Applications
It can be used as a heterogeneous catalyst for various organic reactions:
- Alkoxylation of active hydrogen-containing organic compounds
- Preparation of ethylenically unsaturated carboxylic acids or esters
Phosphor Materials
Barium phosphates find applications as phosphor materials:
- Barium phosphate-based phosphors for imaging plates in computed radiography
- Phosphate phosphors containing Ba(TiZr)PO for light sources, exhibiting high emission intensity and heat stability without rare earth elements
Contrast Agents
Nanostructured one can be used as a contrast agent for micro-computed tomography (micro-CT) imaging:
Provides excellent contrast for visualizing blood vessels and microvasculature in ex vivo mouse brain imaging
Other Applications
- Filler in plastics, coatings, paints, paper, and glass
- Substrate for colored pigment formulations and coatings
- Nucleation center for lead sulfate in lead-acid batteries
- X-ray contrast medium
- Cosmetics and sunscreens (high-quality “permanent white”)
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| Barium Phosphate Catalysts | Enables efficient alkoxylation of organic compounds, and preparation of unsaturated carboxylic acids/esters with high selectivity. | Organic synthesis, fine chemical production, and polymer industry. |
| Barium Phosphate Phosphors | Exhibits high emission intensity, heat stability, and eliminates need for rare earth elements in phosphor materials. | Imaging plates for computed radiography, energy-efficient light sources. |
| Barium Phosphate Contrast Agents | Provides excellent contrast for visualizing blood vessels and microvasculature in ex vivo micro-CT imaging. | Biomedical imaging, preclinical studies, and vascular research. |
| Barium Phosphate Fillers | Imparts desirable properties like opacity, density, and durability to plastics, coatings, paints, and paper products. | Polymer composites, protective coatings, and paper manufacturing. |
| Barium Phosphate Pigments | Acts as a stable substrate for colored pigment formulations and coatings with improved opacity and durability. | Decorative coatings, paints, and inks for various applications. |
Latest Technical Innovations of Barium Phosphate
Synthesis Methods and Process Innovations
- Cyclic Production Method: A cyclic process for preparing barium sulfate and lithium-iron phosphate involving rapid addition of barium hydroxide to an aqueous lithium/sulfate solution at high temperature (>50°C).
- Biosynthesis: Bio-inspired synthesis of its nanoparticles using centrifuged bacteria solution under controlled pH, producing irregular flake-like nanostructures of 20-100nm size.
- Catalytic Conversion: One-step conversion of barium sulfate to barium metaphosphate by high temperature calcination (500°C) with ammonium dihydrogen phosphate.
- Continuous Precipitation: Continuous precipitation of barium sulfate microcrystals by simultaneous mixing of barium and sulfate solutions under controlled pH (1-5), flow rates and stirring for precise size/morphology.
Structural and Compositional Modifications
- Doping: Synthesis of cadmium-doped barium phosphate crystals exhibiting diffuse phase transition and relaxor behavior, with tunable dielectric properties.
- Composite Formation: Preparation of barium phosphate-based chemically bonded phosphate ceramics incorporating barium for improved radiation shielding.
- Phosphor Development: Synthesis of phosphate phosphors like Ba(TiZr)PO with controlled Zr doping (x) for tunable emission intensity and thermal stability without rare earth elements.
Separation and Purification Techniques
- Colloidal Separation: Separation of colloidal barium phosphate/sodium phosphate catalysts from alkoxylated products by water-induced breaking of the colloidal state.
- Acid Treatment: Treatment of di-barium phosphate with volatile acids (HCl, HNO3) to produce soluble barium salts with regeneration of phosphoric acid.
Technical Challenges of Barium Phosphate
| Synthesis of Barium Phosphate Nanoparticles | Developing efficient and scalable methods for the biosynthesis of barium phosphate nanoparticles with controlled size, morphology, and crystallinity. |
| Continuous Precipitation of Barium Phosphate Microcrystals | Optimising the continuous precipitation process for producing barium phosphate microcrystals with precise control over size, shape, and size distribution. |
| Catalytic Conversion of Barium Sulfate to Barium Phosphates | Exploring efficient catalytic routes for the one-step conversion of barium sulfate to barium metaphosphate or other barium phosphate compounds. |
| Doping and Structural Modifications of Barium Phosphates | Investigating the effects of doping and compositional modifications on the structural, dielectric, and relaxor properties of barium phosphate crystals. |
| Cyclic Production of Barium Sulfate and Lithium Phosphates | Developing a cyclic process for the co-production of barium sulfate and lithium-iron phosphate compounds with improved efficiency and yield. |
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