Oxonitridosilicate chlorides—synthesis, single-crystal X-ray and neutron powder diffraction, chemical analysis and properties of Ln4[Si4O3+xN7−x]Cl1−xOx with Ln=Ce, Pr, Nd and x≈0.2

The isotypic oxonitridosilicate chlorides Ln4[Si4O3+xN7−x]Cl1−xOx with Ln=Ce, Pr, Nd and image were obtained by the reaction of the respective rare-earth metals, their oxides and chlorides with “Si(NH)2” in a radiofrequency furnace at temperatures around 1800 °C, using CsCl as a flux. The crystal structures were determined by single-crystal X-ray diffraction (image, no. 198, image, Ce: image, image; Pr: image, image; Nd: image, image) and found to be isotypic with Ce4[Si4O4N6]O. In order to characterize the incorporation of chlorine into the structure, the crystallographic site occupation factors of O, N and Cl were determined by neutron powder diffraction. Furthermore, these results were substantiated by the chemical analyses for Pr4[Si4O3+xN7−x]Cl1−xOx and electron microprobe analyses for all of the synthesized oxonitridosilicate chlorides. Temperature-dependent magnetic susceptibility measurements of the cerium and the praseodymium compound indicate Curie–Weiss behavior with experimentally determined magnetic moments of 2.15(5) μB/Ce and 3.50(5) μB/Pr, respectively. No magnetic ordering could be detected down to 2 K. The 4f1 of cerium has been confirmed by XAS measurements.