I have been reading about some inorganic materials lately, and these three terms confuse me. If they all mean the same thing, would still one of them have preference over others?


2 Answers 2


After some reading I have decided to answer this question myself for anyone else with the same confusion. The info is from the downvoted answer of alphonse and the wiki-link, but with a better overview.

  • Both vitreous and glassy are amorphous. Amorhous is the broadest term to rule them all.

Some amorphous materials have a Glass Transition Temperature (GTT). Above this temperature the material becomes a viscous liquid. note that both below and above the GTT the material is amorphous.

  • An amorphous solid that has a GTT is called a glass.

  • The transition (heating) over the GTT results in a glassy phase.

  • The reverse transition (cooling) corresponding to the GTT is called vitrifcation. The result is a vitreous phase.

If I made mistakes please comment and I will update the answer.


Mostly a matter of preference. BUT. Consider the Glass Transition temperature. (see https://en.wikipedia.org/wiki/Glass_transition). It is important that you understand that while all glasses are, by definition, amorphous, that not all amorphous solids are glasses. Vitrification is the transition from liquid to a glass, such a glass could equally be called vitreous. I wouldn't call a solid, for example a rubber solid, below its Tg to be vitreous, no matter that it is amorphous. (Of course, if a solid is crystalline, then it's outside the context of this discussion.) There are contextual complexities, of course. Silica glass in it's molten state is still glass, while at the same time is not in the glassy state. So, there are different meanings for the term "glass". For instance, I'd not use it for polymers, even though polymer glasses is a legitimate area of molecular dynamics study. Glass in the strictest sense is an solid, amorphous, brittle, rigid, inorganic, transparent material. As you remove those qualifiers the term tends to be used less often. (Some would even argue that glass has to be SiO containing, but I wouldn't go quite that far.) I wouldn't describe a solid as vitreous unless its appearance was "shiny" (and it was brittle), but that may be a personal preference rather than being representative of my technical background. My preference is that amorphous materials be called amorphous. If something can exist in both the liquid and the amorphous solid state, then I'd be comfortable with calling the solid state a glass. For polymers, the question is quite a bit trickier. Many polymers are semi-crystalline. And some (quite a few, actually) amorphous polymers do not exhibit a true liquid state (for example, due to physical cross-links). So, I'd be very cautious about the use of the term glass for them, although in certain contexts its appropriate. I'd avoid the use of "vitreous solid" completely, unless speaking about something after having vitrified.


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