J-Phase solid solution series in the Dy-Si-Al-O-N system

Crystal structure of rare-earth silicon-oxynitride J-phases, Ln4Si2O7N2

“…Liddell et al considered the choice of the unit cell (P2 1 /a or P2 1 /n) for the J-phase with Ln = Y and Dy. 19 The P2 1 /a cells they reported were close to the P2 1 /c cells of ours by replacement of the a-and c-axes. The unit-cell parameters of Y 4 Si 2 O 7 N 2 18 refined by the Rietveld method using the P2 1 /c cell agreed with our results within the standard deviation.…”

“…When the twofold symmetric axis of the monoclinic cell is taken in the b-axis (unique axis), there are three possible cell choices of P2 1 /c, P2 1 /n, and P2 1 /a. 19,23,29 In the structure refinement in this work, we chose the P2 1 /c cell in accordance with "cell choice 1" in the International Tables. 29 As pointed out in the previous studies, 19,23 the values of the c-axis length and β angles of the P2 1 /c cell are very close but different to those of P2 1 /n cell, whereas the a-and b-axes between the P2 1 /c and P2 1 /n cells are common.…”

“…19,23,29 In the structure refinement in this work, we chose the P2 1 /c cell in accordance with "cell choice 1" in the International Tables. 29 As pointed out in the previous studies, 19,23 the values of the c-axis length and β angles of the P2 1 /c cell are very close but different to those of P2 1 /n cell, whereas the a-and b-axes between the P2 1 /c and P2 1 /n cells are common. The relationships between the unit-cell parameters of P2 1 /c and P2 1 /n are expressed as follows:…”

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In these studies using X-ray diffraction method, the crystal structures of the Ln 4 Si 2 O 7 N 2 series were considered to have a cuspidine (Ca 4 Si 2 O 7 F 2 ) type. Recently, we measured the time-of-flight (TOF) neutron powder diffraction data of La 4 Si 2 O 7 N 2 21 and Lu 4 Si 2 O 7 N 2 22,23 synthesized, and refined their structural parameters (unit-cell parameters, atomic coordinates, and occupancies of oxygen and nitrogen atoms in the nonmetal sites) by the Rietveld analysis.…”

“…While R-factors and interatomic distances vary depending on the structure model, it is to be noted that the refined unit-cell parameters between two structure models are close each other. For Er 4 Si 2 O 7 N 2 , the parameters of a = 7.5212(3) Å, b = 10.4109(4) Å, c = 10.7136(5) Å, and β = 109.999(2) • are obtained Wills et al 6,7 [Y,Dy,Er,Yb] Marchand et al 8 [Y,La,Nd,Sm,Gd,Dy,Ho, Er,Yb] Montorsi et al 9,10 [Ce,Pr,Tb,Tm,Lu] Ii et al 12 [La] Mitomo et al 13 [La] Thompson 16 [Y]Liddell et al19 [Y,Dy] …”