Technical specifications determine gallium quality and suitability for applications. This guide explains the standards and measurements.
Gallium Purity Standards
Industry Standard Classifications
4N Grade (99.99% purity)
- Maximum impurity: 100 ppm (parts per million)
- Electronics and research applications
- Most common for investors
- Standard quality level
5N Grade (99.999% purity)
- Maximum impurity: 10 ppm
- Semiconductor manufacturing
- Higher quality applications
- Premium pricing
6N Grade (99.9999% purity)
- Maximum impurity: 1 ppm
- Space and defense applications
- Highest commercial grade
- Significant premium
7N Grade (99.99999% purity)
- Maximum impurity: 0.1 ppm
- Laboratory/specialized use
- Rarely produced
- Experimental applications
Specification Standards
ASTM Standards
- ASTM B777: Standard for High-Purity Gallium
- Defines purity levels
- Establishes test methods
- Specifies documentation requirements
ISO Standards
- ISO 5527: Gallium Metal
- Quality requirements
- Purity definitions
- Testing procedures
Other Standards
- Semiconductor industry specs
- Custom buyer specifications
- Application-specific requirements
- Quality assurance standards
Elemental Composition Specifications
Major Impurity Elements
Silicon (Si)
- Typical limit: <5-10 ppm
- Higher levels affect conductivity
- Critical for semiconductor use
- Checked in all grades
Germanium (Ge)
- Typical limit: <1-5 ppm
- Affects electronic properties
- More critical in high-purity
- Often tested separately
Iron (Fe)
- Typical limit: <1-5 ppm
- Oxidation concern
- Affects purity appearance
- Standard measurement
Copper (Cu)
- Typical limit: <1-5 ppm
- Electrical property impact
- Difficult to remove
- Closely monitored
Tin (Sn)
- Typical limit: <1-3 ppm
- Source from refining
- Affects crystal structure
- Regular check item
Zinc (Zn)
- Typical limit: <1-5 ppm
- Recovery process residue
- Can indicate refining quality
- Standard measurement
Trace Elements
Group I Elements (Al, Na, K)
- Minimum: <0.1-1 ppm each
- Donor impurities
- Affect conductivity
- Less critical
Group II Elements (Ca, Mg, Ba)
- Minimum: <0.1-1 ppm each
- Affect crystal properties
- Lower impact
- Usually acceptable
Rare Earth Elements
- Variable limits
- Application-dependent
- Less frequently measured
- May require special testing
Oxygen & Carbon Content
Oxygen (O)
- Typical limits: <5-20 ppm
- Forms oxide layer
- Affects surface quality
- Important measurement
Carbon (C)
- Typical limits: <1-5 ppm
- Organic contamination risk
- Generally low levels
- Specialty testing
Nitrogen (N)
- Typical limits: <1-3 ppm
- Indicates contamination
- Rare measurement
- Custom requests only
Physical Property Specifications
Density
Theoretical Value
- Gallium density: 5.903 g/cm³ @ 20°C
- Pure gallium standard
- Used to calculate purity
- Physical verification method
Measurement Method
- Measure exact dimensions
- Weigh precisely
- Calculate volume
- Determine density
- Compare to theoretical
Deviation Interpretation
- <0.1% variation: Very pure
- 0.1-0.5% variation: Good purity
-
0.5% variation: Contaminated
Melting Point
Pure Gallium Melting Point
- 29.77°C (85.57°F)
- Liquid below this temperature
- Solid above this temperature
- Purity indicator
Specification Impact
- Pure: Sharp melting point
- Contaminated: Lower melting point
- Impurities depress melting point
- Not commonly tested for purity
Thermal Properties
Thermal Conductivity
- Pure gallium: ~40 W/m-K
- Impurities reduce conductivity
- Application specific
- Less common measurement
Specific Heat Capacity
- Varies with purity
- Affects processing
- Generally not specified
- Research applications mainly
Electrical Properties
Electrical Conductivity
- Decreases with impurity
- Critical for semiconductors
- Purity-dependent
- Application-specific measurement
Resistivity
- Inverse of conductivity
- Pure gallium spec
- Measured in lab testing
- Quality indicator
Crystal Structure Specifications
Crystalline Integrity
Crystal Defects
- Affect semiconductor properties
- Impact electronic performance
- Generally not specified
- Custom testing available
Grain Size
- Uniform preferred
- Affects mechanical properties
- Not usually specified
- Depends on processing
Impurity Distribution
- Uniform distribution desired
- Segregation indicates problems
- Affects local properties
- Not commonly measured
Surface Quality Specifications
Visual Appearance Standards
High-Purity Gallium
- Bright metallic luster
- Reflective surface
- Minimal oxidation
- Clean appearance
Surface Finish
- Smooth ingot surface
- No pitting or corrosion
- Intact protective coating
- Professional appearance
Color
- Silver-white when pure
- Oxidation appears darker
- Uniform color desired
- Visual quality indicator
Surface Oxidation Limits
Acceptable Oxide Layer
- Thin protective layer acceptable
- Mirrors polished surface standard
- Discoloration indicates excess
- Context-dependent standards
Oxide Content Testing
- Optional additional testing
- Increases cost
- Rarely specified
- Custom requirements only
Form & Shape Specifications
Standard Forms
Ingots
- Weight: Typically 100-500g
- Shape: Rectangular block
- Surface: Smooth and flat
- Dimensions: Standardized sizes
Wafers
- Thickness: 2-5 mm typically
- Diameter: 25-100 mm
- Surface: Polished usually
- Purity: High standards
Powder
- Particle size: 100-500 μm typical
- Density: Loose or compacted
- Purity: Same standards
- Handling: Special packaging
Custom Forms
- Application-specific shapes
- Higher cost
- Longer lead times
- Special requirements
Purity Verification Methods
Inductively Coupled Plasma (ICP)
Method Details
- Most accurate technique
- Specifies all elements
- Detects ppb levels
- Industry standard
Typical Analysis
- Silicon, germanium, iron
- Copper, tin, zinc
- All major impurities
- Trace elements optional
Cost & Turnaround
- Cost: $100-500
- Turnaround: 1-2 weeks
- Laboratory-dependent
- Worth the investment
X-ray Fluorescence (XRF)
Method Details
- Non-destructive testing
- Quick elemental analysis
- Surface layer analyzed
- Good for screening
Advantages
- Fast results (hours)
- Non-destructive
- Good for screening
- Lower cost: $50-200
Disadvantages
- Less accurate than ICP
- Surface only
- Depth limited
- Trace elements missed
Other Methods
Gas Chromatography Mass Spec (GC-MS)
- Detects organic contaminants
- Specialized for carbon
- Higher cost: $200-800
- Rarely needed
Atomic Absorption Spectroscopy (AAS)
- Individual element analysis
- Selective method
- Good for specific elements
- Lower cost: $50-100
Specification Documentation
Certificate of Analysis (CoA) Contents
Required Information
- Purity percentage
- Individual impurity levels
- Testing method used
- Test date and analyst
- Laboratory credentials
- Sample identification
Recommended Details
- Uncertainty ranges
- Detection limits
- Reference standards used
- Qualifications noted
- Quality assurance statement
Interpretation Guidelines
Understanding CoA
- "99.99%" means 4N purity
- "< 50 ppm" means below detection limit
- PPM = parts per million
- PPB = parts per billion (1000x lower)
Red Flags
- Vague purity statements
- Missing impurity details
- Unsigned documentation
- Outdated lab information
- Unusual number of significant figures
Application-Specific Specifications
Semiconductor Applications
Requirements
- Minimum 5N purity
- Specific impurity limits
- Oxygen/carbon critical
- Detailed elemental analysis
- Full documentation required
Optoelectronic Applications
Requirements
- Typically 4N-5N
- Silicon content critical
- Purity uniformity important
- Processing history relevant
Research Applications
Requirements
- Variable by application
- 4N often sufficient
- Some require 5N-6N
- Custom specifications common
Aerospace/Defense
Requirements
- Typically 5N-6N minimum
- Full documentation
- Batch traceability
- Radiation testing sometimes
- Certified facilities only
Specification Verification Checklist
Before Purchasing
- [ ] Confirm purity grade matches specification
- [ ] Request full elemental analysis
- [ ] Verify testing methodology
- [ ] Check lab credentials
- [ ] Confirm batch traceability
- [ ] Understand impurity limits
- [ ] Verify form specifications
- [ ] Check surface quality standards
Upon Receipt
- [ ] Verify form and appearance
- [ ] Check weight (±0.5g tolerance)
- [ ] Confirm dimensions
- [ ] Inspect surface condition
- [ ] Match documentation to item
- [ ] Store documentation securely
Resources for Specifications
- Gallium Properties - Physical characteristics
- Purity Grades - Detailed grade information
- Specifications - Complete technical reference
- Evaluate Purity - Quality verification
Key Takeaways
- Understand Grades - Know what 4N, 5N, and 6N mean
- Elemental Analysis - Request detailed impurity specifications
- Physical Properties - Density is key verification method
- Form Standards - Confirm form matches your needs
- Documentation - Always request detailed CoA
- Verification - Test high-value purchases independently
- Application Match - Ensure specifications suit intended use
- Keep Records - Maintain all specification documentation
Disclaimer
This guide provides educational information on technical specifications. Actual specifications may vary by supplier and application. Always consult technical documents and industry standards for precise requirements.