The crucible you run a TGA or DSC sample in is not a trivial choice. The wrong material can react with your sample and distort the mass-loss curve; the wrong volume wastes sample or limits resolution; and a crucible that does not fit your instrument’s holder simply will not run. This guide walks through the three decisions that matter — material, volume and instrument compatibility — and explains why 99% high-purity alumina is the practical default for most thermal analysis work.

What makes a TGA crucible different

In thermogravimetric analysis (TGA) you measure tiny changes in a sample’s mass as it is heated, so anything the crucible itself contributes — a reaction with the sample, a mass change of its own, or uneven heating — shows up as error in your data. That is why crucible selection for thermal analysis is stricter than for general furnace work. The three questions to answer, in order, are: what material will stay inert with your sample, what volume and lid suit your sample mass, and does the crucible fit your instrument.

TGA, DSC and STA: what changes for the crucible

Three related techniques use crucibles, and it helps to know how they differ because each puts slightly different demands on the crucible. TGA (thermogravimetric analysis) tracks mass change versus temperature, so it cares most about the crucible being inert and stable in mass. DSC (differential scanning calorimetry) measures heat flow into or out of the sample, so it favours crucibles with good, repeatable thermal contact — thin-walled aluminum pans for low temperatures, or alumina/platinum for higher ranges. STA (simultaneous thermal analysis) runs TGA and DSC at once on the same sample, so the crucible has to satisfy both: inert and mass-stable for the TGA side, good thermal contact for the DSC side. Alumina handles all three well across the common temperature range, which is part of why it is the default.

The practical takeaway: if you only run low-temperature DSC, a sealed or pierced aluminum pan may be all you need. The moment your work goes above roughly 600°C — which covers most TGA and STA — you are into ceramic or platinum territory, and 99% alumina becomes the sensible default.

1. Material

Material is the first and most important decision because it determines whether the crucible stays inert at temperature. High-purity alumina (99% Al₂O₃) is the default TGA material: it is chemically inert with most samples, withstands oxidising and inert atmospheres, is reusable after cleaning, and is rated for continuous use to about 1600°C. For the great majority of routine TGA — polymers, minerals, pharmaceuticals, ceramics, catalysts — alumina is the correct, economical choice.

Reach for an alternative only when alumina’s limits get in the way. Platinum offers excellent inertness and conductivity but is expensive and can alloy with certain metals and form low-melting eutectics — and it is unsuitable for samples that reduce to free metal. Yttria-stabilised zirconia handles higher temperatures and resists aggressive alkali fluxes better than alumina. Aluminum pans are common in DSC but are limited to roughly 600°C. For the deeper material trade-offs, see our guide on alumina vs zirconia crucibles, or browse the full alumina crucible range.

2. Volume & lid

The crucible volume should match your typical sample mass and the resolution you need. TGA crucibles commonly run from about 25µl up to several hundred microlitres; smaller volumes give faster, more uniform heating and better resolution for small samples, while larger volumes suit bulkier or low-density materials. As a rule, fill to no more than about two-thirds so the sample cannot creep or spit onto the balance. The small-volume cylindrical alumina crucibles are the usual TGA workhorse.

Decide on a lid too. A loose lid (often pierced) reduces sample loss from spattering and gives a more uniform atmosphere over the sample, which improves reproducibility — useful for volatile or powdery samples. An open crucible maximises gas exchange when you want the surrounding atmosphere to reach the sample freely. Match the lid choice to whether your experiment is gas-exchange-limited or loss-limited.

3. Instrument compatibility

A crucible only works if it physically fits your instrument’s sample holder and balance. Thermal analysers from Netzsch, Mettler-Toledo, PerkinElmer and TA Instruments each use specific crucible diameters and heights, so the single most common mistake is ordering a crucible that is the right material but the wrong size for the holder. Before you buy, confirm the outside diameter and height against your instrument’s specification, and check whether your furnace expects a flat-bottom or a particular base profile.

Labmina’s thermal-analysis crucibles are made to standard TGA/DSC dimensions and can be matched to common instrument holders — if you send your instrument model or a drawing, we can confirm the fit. See the thermal analysis crucibles page for the standard range.

The role of atmosphere

The furnace atmosphere interacts with both the sample and the crucible, so it belongs in the selection decision. Under an oxidising atmosphere (air or oxygen) the crucible must not oxidise or react — alumina is fully stable here, which is one reason it dominates routine TGA. Under an inert atmosphere (nitrogen or argon) more materials become viable, but alumina remains an easy, inert default. The case to watch is a reducing atmosphere or samples that release reactive gases: graphite, for example, burns in air and is only usable under inert or reducing gas, and some samples that reduce to free metal can attack platinum. Alumina’s indifference to atmosphere across oxidising and inert conditions is a quiet but real advantage for a general-purpose lab.

Atmosphere also influences your lid choice. If the point of the run is to let a controlled gas reach the sample — oxidation studies, for instance — an open or pierced crucible is correct. If you are studying decomposition and want to limit re-condensation or spitting, a closer lid helps. Decide the atmosphere and the lid together rather than in isolation.

Crucible choice by sample type

Most selection questions resolve quickly once you name the sample. Here is where common sample classes typically land — in nearly all routine cases, 99% alumina is the answer.

• Polymers & plastics: alumina, open or pierced lid, oxidising or inert atmosphere depending on whether you study oxidation or pyrolysis. The standard, low-cost workhorse case.
• Minerals, ceramics & inorganics: alumina to high temperature (calcination, loss-on-ignition). Its 1600°C rating covers almost all of this work.
• Pharmaceuticals & organics: alumina for TGA; thin aluminum pans for low-temperature DSC of melting/transition behaviour.
• Catalysts & carbons: alumina under controlled atmosphere; graphite burns in air, so avoid it for oxidative work.
• Metals & alloys: check for reactions — some alloy with platinum or reduce to free metal; alumina or zirconia is often safer.
• Aggressive fluxes / strong alkalis: not alumina — use zirconia or platinum, which resist these better.

Alumina: the practical default for TGA

Putting the three decisions together, 99% high-purity alumina is the default that covers most thermal analysis work. It is inert with the overwhelming majority of samples, reusable across many runs, available in the small standard volumes TGA needs, and rated comfortably to 1600°C — well above the working range of most TGA experiments. Unless your chemistry or temperature genuinely pushes past alumina’s limits, it is both the technically correct and the most economical choice.

Cylindrical — TGA standard

Conical — easy recovery

Rectangular — batch prep

OEM vs third-party crucibles

TGA crucibles are a consumable: you replace them regularly as they accumulate residue or get damaged, so unit cost matters over a year of running samples. OEM-branded crucibles carry a large premium for what is, in material terms, a standard 99% alumina part. Third-party alumina crucibles made to the same dimensions and purity deliver equivalent performance at a fraction of the cost — the same inertness, the same temperature rating, the same fit, without the brand markup. For a high-volume lab, switching the consumable while keeping the instrument is one of the simplest ways to cut running costs without affecting data quality.

Common mistakes to avoid

A handful of mistakes account for most TGA crucible problems. Knowing them up front saves wasted runs and ruined samples.

• Right material, wrong size. The most frequent error: ordering an inert crucible that does not fit the instrument holder. Always confirm diameter and height against your furnace before buying.
• Working too close to the rating. Alumina is rated to ~1600°C continuous; running right at the limit for long holds invites creep and drift. Leave headroom.
• Overfilling. A crucible filled past about two-thirds can let the sample creep, spit or bridge to the lid, corrupting the mass signal.
• Ignoring atmosphere–material conflicts. Graphite in air, platinum with metal-reducing samples, alumina with alkali fluxes — each is a predictable failure.
• Scraping crucibles clean. Mechanical cleaning sheds particles and damages the surface; re-fire instead.
• Inconsistent sample geometry. Varying mass or fill level between runs makes curves hard to compare; standardise it.

Practical tips for clean data

• Condition new crucibles. Fire them empty once at your working temperature before analytical use to burn off residues and stabilise the surface.
• Use a consistent sample mass and fill level. Reproducible geometry gives reproducible curves; don’t overfill.
• Ramp at a controlled rate. Avoid thermal shock and give the sample time to equilibrate, especially with a lid.
• Match the crucible to the chemistry. Don’t run alkali fluxes in alumina — switch to zirconia or platinum for those.
• Clean by re-firing, not scraping. Mechanical tools damage the surface and shed particles into future samples.

Conclusion

Choosing a TGA crucible comes down to three questions answered in order: material, volume and instrument fit. For the vast majority of thermal analysis, 99% high-purity alumina answers the material question — inert, reusable and rated to 1600°C — leaving you to match volume to your sample and confirm the crucible fits your holder. Reserve platinum and zirconia for the specific cases that need them. If you want help confirming a size for your instrument, see the thermal analysis crucibles range or request a custom size, and read alumina vs zirconia for the full material comparison.

Frequently asked questions