화학공학소재연구정보센터
Inorganic Chemistry, Vol.51, No.1, 282-289, 2012
Structural Frustration and Occupational Disorder: The Rare Earth Metal Polysulfides Tb8S14.8, Dy8S14.9, Ho8S14.9, and Y8S14.8
Dark red crystals of Y8S14.8, Tb8S14.8, Dy8S14.9, and Ho8S14.9 have been obtained following different reaction routes. The isostructural title compounds adopt the Gd8Se15 type, a 24-fold superstructure of the ZrSSi-type and can be described in space group A112 (non standard setting of C121, no. 5) with lattice parameter of a = 11.505(1) angstrom, b = 15.385(1) angstrom, c = 15.726(1) angstrom, and gamma = 90.21(2)degrees for Y8S15-x; a = 11.660(1) angstrom, b = 15.468(2) angstrom, c = 15.844(2) angstrom, and gamma = 90.19(2)degrees for Tb8S15-x; a = 11.584(1) angstrom, b = 15.340(2) angstrom, c = 15.789(2) angstrom, and gamma = 90.34(2)degrees for Dy8S15-x; and a = 11.538(1) angstrom, b = 15.288(2) angstrom, c = 15.740(2) angstrom, and gamma = 90.23(1)degrees for Ho8S15-x, respectively. The structure consists of an alternating stacking of puckered [RES] (RE, rare-earth metals) double slabs and planar sulfur layers along [001]. The planar sulfur layers have a complex arrangement of S-2(2-) dinuclear dianions, isolated S2- ions, and vacancies. All compounds contain trivalent rare-earth metal ions, for Tb8S15-x, and Dy8S15-x antiferromagnetic order was found at T-N = 5.4(2) K and 3.8(1) K, respectively. Short wavelength cutoff optical band gaps of 1.6 to 1.7 eV were determined.