Neutron diffraction study of yttrium ?'-sialon

Luminescence Properties of Terbium-, Cerium-, or Europium-Doped α-Sialon Materials

“…The size of this M cation site is dominated by the (Si, Al) 12 (O,N) 16 network, as demonstrated by almost the same average M-(N,O) distances found for Ca-a-sialon and Y-a-sialon (13), independent of the difference in ionic radius between Ca 2+ (1.06 Å ) and Y 3+ (0.96 Å ). Neutron diffraction did not yield unambiguous information about possible O/N ordering around the M cation, as the oxygen concentration was too low to detect a site preference for this ion (14). EXAFS results obtained for Er-a-sialon (15) and Yb-a-sialon (16) show that two out of the seven anionic positions are preferentially occupied by oxygen ions while the other coordinating positions are occupied by nitrogen ions, indicating an O/N ratio around the metal ion higher than the average matrix value.…”

Structural and Photoluminescence Properties of Ce3+‐ and Tb3+‐Activated Lu‐α‐Sialon

“…1,2 Besides Ca-and Li-stabilized a-Sialon, [13][14][15] it is well-known that trivalent lanthanoids except La 31 , Ce 31 , Pr 31 , and Eu 31 can also be incorporated into the a-Sialon host lattice. [16][17][18][19][20][21][22][23][24] However, up till now, only the crystal structures of Y-a-Sialon and Nd-a-Sialon have been determined for rare earth-stabilized Ln 31 -a-Sialons. 14,[16][17][18] In addition, because the types of the rare earth ions Ln, where the activator ions partially occupy on, have considerable effects on the crystal field strength acting on the Ln ions and on the luminescence properties, especially for the 5d states of Eu 21 and Ce 31 because the 5d orbitals in the excitation states involve in the formation of chemical bond of Ln-N/O (Ln 5 Eu 21 and Ce 31 ).…”

Time-of-flight Rietveld neutron structure refinement and quantum chemistry study of Y-α-sialon

“…Cao et al 8 presented a constant wavelength Rietveld neutron refinement of Y-␣-sialon based on powder data collected using rather long wavelength (2.5718Å), which seriously limited the number of Bragg diffractions in the pattern. No details either on the N versus O ratios used in the refinement or on chemical analysis were given, but due to the large difference in N/O scattering lengths, only N atoms were considered.…”