Crystals with a hexagonal lath-like morphology were found in glass products for cathode ray tubes. These crystals are preserved at the interfaces between glass and ZrO
2 ceramics in a glass melting tank. An electron microprobe analysis gives SiO
2: 45.6, ZrO
2: 31.5, K
2O: 19.0, Na
2O: 1.92, BaO: 1.46, SrO: 0.33, in wt%. These values and X-ray analyses indicated the crystals to be precipitated with the same structure as mineral wadeite, K
2ZrSi
3O
9, whose K atom sites are partially substituted by Ba, Sr or Na atoms. The structure is hexagonal with the space group P6
3/m, and the unit cell dimensions of a=6.918(2) and c=10.151(3)Å. The structure was refined using X-ray diffraction intensities from a single crystal. The bond distances and angles for Si
3O
9 rings are well comparable with those of benitoite, BaTiSi
3O
9, which is another example mineral including Si
3O
9 rings, with slight but significant difference in non-bridging Si-O bond distances. The mean square displacements of atoms in Si
3O
9 rings show that the tetrahedron is rigid for Si-O bond but strongly distorted for the O-O edges of non-bridging O atoms during thermal vibrations, coordinating to Zr and K. The thermal vibrational behaviors for the non-bridging oxygen are significantly different from those in benitoite.
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