Purity 99.99999% · CAS 7440-50-8 · Cu
Copper 99.99999% (7N) — research grade, limited availability
Research quantities only — zone-refined
Overview
Seven-nines copper exists in gram to low-kilogram quantities, produced by repeated zone refining and verified by GDMS. It is made to order rather than held in stock. Practically it is used as bulk metal or rod; converting it to powder without picking up oxygen is itself a specialist step.
Typical trace impurities
| Impurity | Typical max |
|---|---|
| Total metallic | ≤ 0.1 ppm |
| U + Th | ≤ 0.0001 ppm |
Indicative values. The certificate of analysis for your lot is the binding document.
Where this grade is used
- ▪Cryogenic and low-temperature physics (RRR measurements)
- ▪Fundamental materials research
- ▪Isotope and neutrino detector components
Common forms
Rod, ingot, foil; powder on special request
Specification at a glance
| Material | Copper Powder (Cu) |
|---|---|
| Purity | 99.99999% (7N), metals basis |
| CAS | 7440-50-8 |
| Production route | Electrolytic refining followed by inert-gas atomisation and zone-refined feedstock control |
| Available forms | Rod, ingot, foil; powder on special request |
| Analysis method | GDMS (glow-discharge mass spectrometry) full trace scan |
| Documentation | Certificate of analysis per lot, RoHS and REACH statements, country of origin, full GDMS scan and conflict-minerals declaration on request |
| Typical packaging | 50 g argon-sealed jar · 500 g · 5 kg · Bulk drums |
What 99.99999% (7N) actually means
7N is shorthand for 99.99999% purity on a metals basis: at most 0.00001% of the material, by weight, is something other than Cu. The metals-basis convention excludes dissolved gases and, for powders, surface oxygen — which is why oxygen is quoted separately in the trace table below.
Two lots at the same nominal purity are not interchangeable if the residual elements differ. For this grade the limiting element is typically Total metallic at ≤ 0.1 ppm. What matters is which impurities your process is sensitive to — judge a lot on its full trace analysis, not on the headline number.
Choosing 7N versus the neighbouring grades
Coming from 99.9999% (6N): the step up buys you tighter trace control for research quantities only — zone-refined. If your process tolerates the residuals of 6N, the lower grade remains the more economical and more widely available choice.
When in doubt, qualify both adjacent grades on a sample and run your own incoming inspection before committing a process to either.
Quality control and traceability
Copper Powder at 99.99999% is normally released against a lot-specific certificate of analysis stating the assay, the trace elements measured and the method used (GDMS (glow-discharge mass spectrometry) full trace scan). Well-run lots stay traceable from the refinery batch through to the container that reaches the laboratory.
- ▪A retained sample per lot, so a later question can be re-tested against the original material
- ▪Independent third-party verification, used when the assay is contractually critical
- ▪Incoming inspection on the receiving side — the certificate states the method, not the result you will measure
Handling, storage and shipping
- ▪Fine copper powder oxidises at the surface; keep containers sealed and open them under inert gas or dry air for grades from 5N upward.
- ▪Sub-45 µm cuts are classified as a combustible dust — ground equipment, avoid dust clouds and follow ATEX or NFPA 484 practice on site.
- ▪Store between 5 °C and 30 °C at low humidity, away from ammonia, acids and sulphur compounds.
Frequently asked questions
Common questions from buyers specifying copper powder at 99.99999%.
- Is 99.99999% copper powder the right grade for my application?
- It is the usual choice for research quantities only — zone-refined. Below it, 99.9999% (6N) covers less demanding work at lower cost. It is the highest grade we list for this material.
- What does the 7N designation mean?
- The N notation counts the nines in the assay: 7N equals 99.99999% Cu on a metals basis, with the balance made up of the trace elements listed in the analysis table.
- Which impurities are measured and reported?
- GDMS (glow-discharge mass spectrometry) full trace scan is used, and a certificate of analysis reports each element in the table above, starting with Total metallic at ≤ 0.1 ppm. The scope of a scan can be widened to further elements when a process is sensitive to one in particular.
- How is this grade normally packed?
- 50 g argon-sealed jar, 500 g, 5 kg, Bulk drums. Sub-45 µm cuts are classified as a combustible dust — ground equipment, avoid dust clouds and follow ATEX or NFPA 484 practice on site.
- Which forms is 99.99999% copper powder available in?
- Commonly: rod, ingot, foil; powder on special request. The form is often a bigger practical constraint than the assay itself, because the last processing step has to preserve the purity already achieved.