Custom fused silica crucibles · Clear, opaque, and double-layer
Quartz Crucible
A quartz crucible — also called a fused quartz crucible or fused silica crucible — is a high-purity fused silica vessel used to hold, heat, and melt materials at high temperature with minimal contamination. It is used for laboratory ashing, acid digestion, and trace-element analysis, for calcination and heat treatment, and for high-temperature melts such as Czochralski (CZ) silicon crystal pulling.
FGQuartz manufactures clear and opaque fused silica crucibles with SiO₂ ≥ 99.99% in round-bottom, flat-bottom, cylindrical, conical, and rectangular forms, with or without lids. Diameter, height, wall thickness, base, rim, spout, flange, threaded neck, and capacity follow the customer drawing, including CZ-grade double-layer construction. Custom manufacturing is available from a single prototype, with no minimum order quantity.
Quick answer
What is a fused quartz crucible used for?
Fused quartz crucibles contain high-temperature melts and chemical reactions with minimal contamination, most notably in Czochralski (CZ) silicon crystal pulling, high-temperature calcination, and laboratory acid digestion or trace-element analysis.
Key takeaways
- A cylindrical quartz crucible has a uniform wall diameter from top to bottom, giving even heat distribution and a stable seating fit.
- CZ crucibles are double-layer: an opaque outer layer for insulation and strength, and a clear, bubble-free inner layer that touches the melt.
- Laboratory crucibles can be reused across cycles if cleaned; CZ crucibles are generally single-use.
- Quartz is chemically inert and non-conductive; graphite tolerates higher temperatures but can add carbon. Not for HF, hot concentrated phosphoric acid, or molten alkali fluxes.
Written by the FGQuartz Engineering Team · Updated November 2026
On this page: Specifications · Choosing a crucible · Comparisons · Crucible types · Project examples · Applications · FAQ and quote
Lead time depends on size and drawing complexity; the quote confirms the schedule.
Key features of quartz crucibles
Product features
Quartz crucible specifications
Technical specifications
Values below describe the standard build for fused silica crucibles. Dimensions, wall, and tolerances are set from the drawing and confirmed in design-for-manufacture (DFM) review.
| Parameter | Specification |
|---|---|
| Material | High-purity fused quartz / fused silica (SiO₂ ≥ 99.99%). Clear or opaque fused silica. |
| Shape | Round-bottom, flat-bottom, cylindrical, conical, rectangular, and boat-style crucibles. |
| Construction | Single-layer crucibles, and CZ-grade double-layer crucibles with an opaque outer layer and a clear, bubble-free inner layer. |
| Diameter and height | Made to drawing. No published SKU size chart. |
| Capacity | Follows the diameter, height, and wall on the drawing, including non-standard capacities. |
| Wall thickness | Specified on the drawing, from thin-wall analytical crucibles to heavy-wall melting crucibles. |
| Rim, spout, and neck | Plain, flared, or fire-polished rim; pouring spout, flange, or threaded neck when required. |
| Lids | Matching quartz lids, flat or domed, ground or loose-fit to drawing. |
| Working temperature | Continuous to 1200°C (2192°F), short-term to 1300°C (2372°F). |
| Purity | SiO₂ ≥ 99.99%. Trace metals and OH vary by grade. |
| Surface finish | Fire-polished or as-formed, annealed after hot work. |
| Processing | Diamond cutting, CNC machining, oxy-hydrogen flame forming and welding, fire polishing, annealing. |
| Customization | Build-to-print from DXF, STEP, IGES, or PDF, or from a qualified sample. Single prototypes through production. No MOQ. |
Full thermal, mechanical, optical, and chemical tables: Technical Specifications. Tolerances and capacity are set per drawing — they are not catalog numbers.
Clear, opaque, or double-layer: choosing the crucible
Crucible selection
Clear fused quartz crucibles suit laboratory work, where you want to see the sample, and clean high-temperature heating with a low analytical blank. Opaque fused silica crucibles scatter infrared, insulate better, and spread heat more evenly, which helps in melting and heat-treatment furnaces. Cylindrical crucibles have a uniform wall from top to bottom rather than a tapered shape, which gives even heat distribution and a stable fit in the furnace. Double-layer CZ crucibles combine an opaque outer layer for strength and insulation with a clear, bubble-free inner layer that contacts the silicon melt.
Quartz glass, fused quartz, and fused silica all describe amorphous high-purity SiO₂: fused quartz is melted from natural quartz crystal, fused silica is synthetic, usually from SiCl₄. Send the material to be heated, peak temperature, atmosphere, and volume so grade, wall, and shape can be matched. Background: What is quartz glass?
Typical properties of fused silica
Typical values for high-purity fused silica. Optical transmission and OH content vary by grade.
| Continuous service | 1200°C (2192°F) |
| Short-term maximum | 1300°C (2372°F) |
| Softening point | ≈ 1680°C (3056°F) |
| Annealing point | ≈ 1215°C (2219°F) |
| Strain point | ≈ 1120°C (2048°F) |
| Thermal expansion (20–300°C) | 5.5 × 10⁻⁷ /°C |
| Thermal conductivity (20°C) | ≈ 1.4 W/(m·K) |
| Density | ≈ 2.2 g/cm³ |
Chemical note: excellent resistance to HCl, HNO₃, H₂SO₄, aqua regia, and organic solvents. Attacked by HF, hot concentrated phosphoric acid, and hot strong alkalis. Also attacked by molten alkali fluxes such as NaOH and Na₂CO₃; confirm compatibility before melting reactive metals.
Laboratory crucible vs CZ crystal-growth crucible, and quartz vs graphite
Comparison
Laboratory crucible vs CZ crystal-growth crucible
| Point | Laboratory crucible | CZ crystal-growth crucible |
|---|---|---|
| Typical use | Ashing, acid digestion, calcination, thermal analysis. | Holding the silicon melt during Czochralski crystal pulling. |
| Construction | Single-wall clear or opaque fused silica. | Double layer: opaque outer, clear bubble-free inner. |
| Contact surface | Clear or opaque wall, as specified. | Clear, bubble-free inner layer to minimize contamination. |
| Reuse | Typically reusable across cycles if properly cleaned. | Generally single-use because of extreme thermal cycling. |
Quartz crucible vs graphite crucible
| Point | Quartz crucible | Graphite crucible |
|---|---|---|
| Maximum temperature | About 1200°C (2192°F) continuous; short-term to 1300°C (2372°F). | Much higher. |
| Contamination | Chemically inert and electrically non-conductive; no carbon. | Can introduce carbon pickup. |
| Visibility | Clear grades allow visual checks. | Opaque. |
| Best for | Processes where carbon or electrical contamination must be avoided. | Very high-temperature processes where carbon is acceptable. |
Quartz crucible types we fabricate
Customization
FGQuartz does not publish a fixed crucible size list. Each crucible is made to your sample, furnace, and process, from a single prototype to production, with no minimum order quantity. Non-crucible custom parts are on the custom quartz glass page.
| Crucible type | Typical use | What is fabricated |
|---|---|---|
| Laboratory crucibles | Ashing, sample prep, and thermal analysis | Clear, thin-wall crucibles in round-bottom or flat-bottom form, with optional lids. |
| Cylindrical crucibles | Even heating and stable seating in the furnace | Crucibles with a uniform wall diameter from top to bottom, to drawing. |
| Melting crucibles | High-purity melting and heat treatment | Heavy-wall clear or opaque fused silica crucibles sized to the furnace and charge. |
| CZ crystal-growth crucibles | Czochralski silicon crystal pulling | Double-layer crucibles with an opaque outer layer and a clear, bubble-free inner layer. |
| Opaque crucibles | Furnaces needing better insulation and even heating | Opaque fused silica crucibles cut, formed, and finished to drawing. |
| Crucibles with lids | Atmosphere control and reduced evaporation | Matching quartz lids, flat or domed, with vent holes on request. |
| Boat-style crucibles | Tube-furnace heating and combustion | Open trough crucibles in custom lengths that slide into a furnace tube. |
| Custom crucibles | OEM and non-standard vessels | Build-to-print or reverse-engineered crucibles with flanges, threaded necks, spouts, handles, or drilled features. |
Representative crucible builds
Project examples
Three typical custom crucible projects, described by the requirement, the build route, and what is checked against the drawing. Customer names and confidential drawing data are withheld.
01 · Laboratory
Thin-wall analytical crucible with lid
Requirement. A clean, low-blank vessel for ashing and sample preparation.
How it is built. Clear fused silica body formed from tube stock, rim fire-polished, matching lid ground to fit, annealed after hot work.
Checked against the drawing. Diameter, height, wall thickness, and lid fit.
02 · Furnace processing
Cylindrical melting crucible
Requirement. A uniform-wall vessel that seats stably and heats evenly in a batch furnace.
How it is built. Heavy-wall clear or opaque fused silica formed to a cylindrical body with a fire-polished rim, then annealed.
Checked against the drawing. Outer diameter, height, wall thickness, and rim condition.
03 · Custom vessel
Crucible with spout and threaded neck
Requirement. A non-standard vessel that pours cleanly and connects to existing equipment.
How it is built. Body formed to drawing, pouring spout flame-formed, threaded neck CNC-machined, fire-polished and annealed.
Checked against the drawing. Capacity, spout geometry, thread form, and overall height.
Formed, finished, and annealed under one ISO 9001 system
Manufacturing and quality
FGQuartz operates a 15,000 m² facility in Lianyungang covering CNC diamond machining, oxy-hydrogen flame forming, welding, fire polishing, and annealing, so crucibles are formed and finished in one plant. Learn more about FGQuartz.
Handling and cleaning: clean with an acid bath or alcohol wipe before high-temperature use, because alkali salts and fingerprints catalyze devitrification above roughly 1150°C. Heat and cool at a controlled rate and lift with tongs that do not chip the rim.
Quartz crucible applications
Applications
Quartz crucible manufacturer: why specify FGQuartz
Manufacturer
Quartz crucible FAQ
Procurement questions
What is a fused quartz crucible used for?
Fused quartz crucibles contain high-temperature melts and chemical reactions with minimal contamination, most notably in Czochralski (CZ) silicon crystal pulling, high-temperature calcination, and laboratory ashing, acid digestion, and trace-element analysis.
Should I choose a clear, opaque, or double-layer crucible?
Clear crucibles suit laboratory work where you want to see the sample and need a low analytical blank. Opaque fused silica insulates better and spreads heat more evenly in melting and heat-treatment furnaces. Double-layer CZ crucibles combine an opaque outer layer for strength and insulation with a clear, bubble-free inner layer that contacts the silicon melt.
Are quartz crucibles reusable?
Laboratory crucibles can typically be reused across cycles if properly cleaned. CZ crystal-growth crucibles are generally single-use because of extreme thermal cycling.
What is the difference between a quartz crucible and a graphite crucible?
Quartz is chemically inert and electrically non-conductive, adds no carbon, and clear grades allow visual checks, but it is limited to about 1200°C (2192°F) continuous and 1300°C (2372°F) short-term. Graphite tolerates much higher temperatures but is opaque and can introduce carbon pickup.
What can not be heated in a quartz crucible?
Quartz is attacked by HF, hot concentrated phosphoric acid, and hot strong alkalis, including molten alkali fluxes such as NaOH and Na₂CO₃. Confirm compatibility before melting reactive metals.
What shapes and sizes can you make?
Round-bottom, flat-bottom, cylindrical, conical, rectangular, and boat-style crucibles, with or without lids, to your drawing. Diameter, height, wall, rim, spout, flange, threaded neck, and capacity follow the drawing; there is no fixed size chart, and a qualified sample can be matched.
How should I clean and handle a quartz crucible?
Clean with an acid bath or alcohol wipe before high-temperature use, because alkali salts and fingerprints catalyze devitrification above roughly 1150°C. Heat and cool at a controlled rate and lift with tongs that do not chip the rim.
What are the minimum order quantity, lead time, and quote process?
There is no minimum order quantity; single prototypes are welcome. Custom builds typically take 3–6 weeks depending on size and drawing complexity, and the quote confirms the schedule. Send a drawing (DXF, STEP, IGES, or PDF), a sample, or the material, peak temperature, and volume; replies typically arrive within 24 business hours.
Related pages
Keep reading
Quartz wafer boats
Horizontal, vertical, and solar wafer carriers.
Quartz glass tubes
Custom fused silica tubes, OD 5–1000 mm, built to your drawing.
Laboratory quartz glass
Quartzware for ashing, digestion, and thermal analysis.
What is quartz glass?
How quartz glass, fused quartz, and fused silica relate.
Technical specifications
Thermal, mechanical, optical, and chemical tables for fused silica.
Custom quartz glass
Build-to-print quartz parts from a single prototype to production.