Amorphous Stuff It is known for many, many years, that heating a zeolite at elevated temperatures (called calcination) leads above a certain temperature to an amorphous or dense crystalline product. Often the dense crystalline material is formed out of the amorphous "intermediate state". Therefore -in my eyes - it is absolutely not astonishing, that heating a FAU type Zeolite to 1000°C leads to an amorphous Silica/Alumina compound with -in this case- incorporated Bismut. Thus, a known method for producing amorphous compounds does its job and produces a material which has similar properties as already exsisting amorphous compounds (Bi-Glas). Ok, I might not get the point of this paper, especially as "Advanced Materials" is a high quality journal, but what’s new and remarkable? I have some more nitpicker remarks and questions: -How the hack can the proposed Bi+ be formed? What is reducing Bi3+ in a Zeolite in Ar Atmosphere at 900°C ? The Zeolite itself? The Argon? Did I miss something? -As Zeolites are less dense than the formed dense materials at elevated temperatures, it is certainly true, that if you compare the luminescence spectra of samples of _same_ volume, with the denser material you have more solid matter (and in this case especially more luminescating species) in your sample holder. Has anyone taken care of this effect? I could not figure this out from the experimental part, but I assume that the authors took care. Regards Frank