A small sealed Ta crucible for thermal analysis of volatile metallic samples

Differential thermal analysis on metallic alloys containing volatile elements can be highly problematic. Here we show how measurements can be performed in commercial, small-sample, equipment without modification. This is achieved by using a sealed Ta crucible, easily fabricated from Ta tubing and sealed in a standard arc furnace. The crucible performance is demonstrated by measurements on a mixture of Mg and MgB$_2$, after heating up to 1470$^{\circ}{\rm C}$. We also show data, measured on an alloy with composition Gd$_{40}$Mg$_{60}$, that clearly shows both the liquidus and a peritectic, and is consistent with published phase diagram data.