Oxonitridosilicate chlorides—synthesis, single-crystal X-ray and neutron powder diffraction, chemical analysis and properties of Ln4[Si 4O 3+xN 7−x]Cl 1−xO x with Ln=Ce, Pr, Nd and x≈0.2

Abstract

The isotypic oxonitridosilicate chlorides Ln 4[Si 4O 3+ x N 7− x ]Cl 1− x O x with Ln=Ce, Pr, Nd and x ≈ 0.2 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 ( P 2 1 3 , no. 198, Z = 4 , Ce: a = 10.4461 ( 12 ) pm , R 1 = 0.0524 ; Pr: a = 10.3720 ( 12 ) pm , R 1 = 0.0415 ; Nd: a = 10.3618 ( 12 ) pm , R 1 = 0.0257 ) and found to be isotypic with Ce 4[Si 4O 4N 6]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 Pr 4[Si 4O 3+ x N 7− x ]Cl 1− x O x 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) μ B/Ce and 3.50(5) μ B/Pr, respectively. No magnetic ordering could be detected down to 2 K. The 4 f 1 of cerium has been confirmed by XAS measurements.