All Glossary

LAS Body

An LAS body is a ceramic body based mainly on the lithium–alumina–silica system:

L = lithium oxide, Li₂O
A = alumina, Al₂O₃
S = silica, SiO₂

During firing, these oxides can form low-expansion lithium aluminosilicate crystalline phases, especially β-spodumene or β-eucryptite. LAS ceramics can have extremely low, near-zero, or even slightly negative thermal expansion, giving them exceptional resistance to thermal shock. That makes it useful for stovetop cookware, cooktop panels, kiln furniture and other products exposed to sudden temperature changes. However, it is not enough simply to mix spodumene, kaolin and silica. Particle size, oxide proportions, firing temperature, soak time and cooling curve determine which crystalline and glassy phases actually develop.

Developing a Cone 6 LAS Body

There is no universal “best temperature” for an LAS body. For a clay/mineral-derived body containing spodumene, roughly 1150–1250°C is a plausible development range, making cone 6 (about 1200–1220°C) a reasonable target. The optimum is the lowest temperature that produces adequate densification and strength while developing the desired low-expansion phases. Glaze fit is however, especially difficult because most ordinary pottery glazes expand substantially more than a well-developed LAS body. Even a glaze regarded as “low expansion” for stoneware might be far too high for it.

Several temperature events matter, these can be detected by physical testing

• About 900–1100°C: Natural α-spodumene converts irreversibly to β-spodumene. This transformation involves a substantial structural and volume change, potentially creating microcracks or porosity if coarse spodumene particles remain.
• About 1100–1250°C: Reactive sintering between spodumene, mullite and added silica can develop the intended lithium-aluminosilicate while densifying the body.
• Above the useful maturity window: The increasing liquid phase may close porosity and can also cause deformation, lithium volatilization, dissolution of the desired crystals into glass and an increase in thermal expansion.

For each mixture of lithium feldspar, silica test for these:

At every temperature, measure:

• firing shrinkage and absorption;
• bulk density and warpage;
• strength;
• actual thermal expansion by dilatometer;
• phases by XRD, if available;
• thermal-shock survival;
• microcracking before and after thermal cycling.

If you want to make an LAS glass-ceramic rather than a conventional particulate reactively sintered ceramic body, the process is different. It normally involves first producing a glass and then using separate nucleation and crystallization treatments—often within approximately 600–1000°C, depending heavily on composition and nucleating agents. That should not be confused with firing a spodumene–kaolin ceramic body directly to cone 6.

Related Information

Links

PayPal	No tracking, No ads, No paywall, No transient content! Just organized, concise information constantly updated and improved. Was this helpful? Consider supporting me.

By Tony Hansen Follow me on

Got a Question?

Buy me a coffee and we can talk