TY - JOUR
T1 - New uranium chalcoantimonates, RbU2SbS8 and KU2SbSe8, with a polar noncentrosymmetric structure
AU - Choi, Kyoung Shin
AU - Kanatzidis, Mercouri G.
PY - 1999
Y1 - 1999
N2 - The new compounds, RbU2SbS8 and KU2SbSe8, were prepared as golden-black, blocklike crystals by the polychalcogenide molten flux method. RbU2SbS8 crystallizes in the monoclinic space group Cm with a = 7.9543(9) ̊, b = 11.0987(13) ̊, c = 7.2794(10) ̊, β= 106.030(2)°, and Z = 2. The compound has a two-dimensional character with layers running perpendicular to the c-axis. The coordination geometry around the U4+ atoms is best described as a bicapped trigonal prism. The trigonal prisms share triangular faces with neighboring prisms, forming one-dimensional columns along the α-axis. The columns are then joined to construct sheets by sharing capping S atoms. Sb3+ ions are sitting at the center of a slightly distorted seesaw coordination environment (CN = 4). Rb+ ions are stabilized in 8-coordinate bicapped trigonal prismatic sites. KU2SbSe8 crystallizes in the monoclinic space group Cm with a = 11.5763-(2) ̊, b = 8.2033(1) ̊, c = 15.2742(1) ̊, β= 112.22(2)°, and Z = 4. KU2SbSe8 has essentially the same structure as RbU2SbS8. However, Sb3+ and K+ ions appear disordered in every other layer, resulting in a different unit cell. RbU2SbS8 is a semiconductor with a band gap of 1.38 eV. The band gap of KU2SbSe8 could not be determined precisely due to the presence of overlapping intense f-f transitions in the region (0.5-1.1 eV). The Raman spectra show the disulfide stretching vibration in RbU2SbS8 at 479 cm-1 and the diselenide stretching vibration in KU2SbSe8 at 252 cm-1. Magnetic susceptibility measurements indicate the presence of U4+ centers in the compounds. The compounds do not melt below 1000 °C under vacuum.
AB - The new compounds, RbU2SbS8 and KU2SbSe8, were prepared as golden-black, blocklike crystals by the polychalcogenide molten flux method. RbU2SbS8 crystallizes in the monoclinic space group Cm with a = 7.9543(9) ̊, b = 11.0987(13) ̊, c = 7.2794(10) ̊, β= 106.030(2)°, and Z = 2. The compound has a two-dimensional character with layers running perpendicular to the c-axis. The coordination geometry around the U4+ atoms is best described as a bicapped trigonal prism. The trigonal prisms share triangular faces with neighboring prisms, forming one-dimensional columns along the α-axis. The columns are then joined to construct sheets by sharing capping S atoms. Sb3+ ions are sitting at the center of a slightly distorted seesaw coordination environment (CN = 4). Rb+ ions are stabilized in 8-coordinate bicapped trigonal prismatic sites. KU2SbSe8 crystallizes in the monoclinic space group Cm with a = 11.5763-(2) ̊, b = 8.2033(1) ̊, c = 15.2742(1) ̊, β= 112.22(2)°, and Z = 4. KU2SbSe8 has essentially the same structure as RbU2SbS8. However, Sb3+ and K+ ions appear disordered in every other layer, resulting in a different unit cell. RbU2SbS8 is a semiconductor with a band gap of 1.38 eV. The band gap of KU2SbSe8 could not be determined precisely due to the presence of overlapping intense f-f transitions in the region (0.5-1.1 eV). The Raman spectra show the disulfide stretching vibration in RbU2SbS8 at 479 cm-1 and the diselenide stretching vibration in KU2SbSe8 at 252 cm-1. Magnetic susceptibility measurements indicate the presence of U4+ centers in the compounds. The compounds do not melt below 1000 °C under vacuum.
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U2 - 10.1021/cm990320l
DO - 10.1021/cm990320l
M3 - Article
AN - SCOPUS:0001539736
SN - 0897-4756
VL - 11
SP - 2613
EP - 2618
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 9
ER -