J-Phase Structures in the Y-Si-Al-O-N System

摘要

Preparative studies carried out on compositions lying between Y_4Si_2O_7N_2(J-phase) and Y_4Al_2O_9 (YAM) show similar variations in structure to those already reported for related compositions in the analogous Dy-Si-Al-O-N system. Careful studies of X-ray diffraction patterns confirm that whereas all compositions have a cuspidene-like structure, there is a marked change in the a and b unit cell dimensions for x values in excess of approximately 0.8 in the general formula Y_4Si_(2-x)Al_xO_(7+x)N_(2-x), with much smaller changes in the c unit cell dimension and in the β angle. The results are compared with similar data previously presented for J-phase structures in the Dy-Si-Al-O-N system.