Synthesis and Crystal Chemistry of Oxysulfides with the Garnet Structure,

摘要

In a search for new ternary materials with potential suitability for 10.6micrometer window applications,the sulfur analogs of the garnet structure were investigated. Pure sulfur end-member garnets cannot be synthesized under ambient pressures. A series of oxysulfide garnets with sulfur to oxygen ratios of 7.5/4.5were discovered. These have the general formula (Ln3(VIII)Me2(VI)Me3(IV)O4.5S7.5) where Ln is any rare earth except La(3+) and Me is a variety of 2+, 3+,and 4+transition metal ions plus Mg(2+) and Ga(3+). A total of more than 40compounds have been synthesized and are characterized by x-ray diffraction data. IR spectra of selected garnets indicate that the highest frequency transverse optic mode lies in the range of 470/cm. Complex spectra from two garnets indicate the possibility of anion ordering. (Modified author abstract)