Consider a normal opaque alumina crucible. I've heard that they become transparent at higher temperatures and therefore, are not appropriate for high precision DSC (caloric) measurements. The reason is, that there might be a lack of energy due to radiation losses (in addition to the bad thermal conductivity).
I was not able to find at least one quotable source for this claim. So my two questions are:
- Is this actually right?
- Does someone know of a quotable source for this (scientific papers, textbooks, etc...)?
Edit: Based on my research, the absorption rises with temperature, so the transparency should degrease, what is a somewhat contradictory to A.K. answer, isn't it?