Factory guidance for getting the longest service life out of magnesium oxide crucibles — do not vacuum sinter, heat evenly, control the ramp rate at about 3 °C per minute, and respect the limited corrosion resistance of MgO.
Magnesia crucibles are not suitable for vacuum sintering. Do not run an MgO crucible in a vacuum furnace. If your process genuinely requires a vacuum atmosphere, select a crucible material that is rated for vacuum service instead.
Always heat the crucible evenly. Uneven heating concentrates thermal stress in one part of the wall and is one of the most common causes of cracking. Position the crucible so that heat reaches all sides uniformly, and avoid setting it directly against a heating element or inside a localised hot zone.
Do not subject a magnesia crucible to sudden temperature change — neither rapid heating nor rapid cooling. Taking a hot crucible out into cold air, or placing a cold crucible directly into a hot furnace, will crack it. Ramp the temperature up and down gradually, and let the crucible cool down inside the furnace to near room temperature before you remove it.
Ramp the temperature at approximately 3 °C/min. This slow, controlled rate lets the whole crucible expand uniformly and is the single most effective thing you can do to extend its service life. Heating faster than this is the most common reason a magnesia crucible fails early.
Magnesia has limited corrosion resistance. MgO is a basic oxide and is attacked by acids and by strongly acidic melts — it is best suited to basic and neutral melts. Do not use a magnesia crucible with acidic fluxes or acidic sample matrices; for acidic work, choose an acid-resistant crucible material instead.
Can I vacuum sinter in an MgO crucible?
No. Magnesia crucibles are not intended for vacuum service — use an alternative material rated for vacuum.
What heating rate should I use?
About 3 °C/min. Ramp gradually rather than driving the furnace up quickly.
My crucible cracked — what most likely caused it?
In most cases it is thermal shock: heating or cooling too quickly, or heating unevenly. Review your ramp programme and the crucible's position in the furnace.
Can I use it with acidic samples?
No. MgO is a basic oxide with limited corrosion resistance and is attacked by acidic melts. Use it for basic and neutral melts only.
How do I cool it down?
Cool gradually inside the furnace to near room temperature before removing the crucible.
Magnesia (MgO) crucibles are rigid but brittle and sensitive to thermal and chemical shock. Always handle them with clean gloves, support the base, and avoid dropping, tapping or scraping the walls.
Ramp and cool slowly, generally no faster than about 5 to 10 degrees Celsius per minute, and avoid quenching. Rapid temperature changes create thermal stress that can crack the crucible.
Magnesia resists alkaline melts, many metal oxides and high-temperature fluxes. It reacts with acids, strongly acidic fluxes and with water vapour at high temperature, so confirm compatibility with your specific melt before use.
Let it cool fully, brush out loose residue, then leach soluble salts with warm water or a compatible mild acid. Do not soak in hydrofluoric or strong acids, which attack MgO, and avoid abrasive scrubbing that chips the surface.
Store them in a dry place, because MgO slowly absorbs moisture and carbon dioxide from the air. Keep them with a desiccant for long-term storage and avoid stacking that causes chipping.
Scuvette has manufactured high-purity laboratory ceramics and quartz optics since 2010. Crucibles are produced under an ISO 9001:2015 quality management system (Certificate NOA2408337) and are RoHS compliant (SGS report TAOEC26010238501). No minimum order quantity; custom sizes and OEM service are available.