Oxonitridosilicate chlorides-synthesis, single-crystal X-ray and neutron powder diffraction, chemical analysis and properties of Ln(4) Si4O3+N-x(7-x) Cl1-xOx with Ln = Ce, Pr, Nd and x approximate to 0.2

Lieb, Alexandra, Weller, Mark T., Henry, Paul F., Niewa, Rainer, Pöttgen, Rainer, Hoffmann, Rolf-Dieter, Höfer, Heidi E. and Schnick, Wolfgang (2005) Oxonitridosilicate chlorides-synthesis, single-crystal X-ray and neutron powder diffraction, chemical analysis and properties of Ln(4) Si4O3+N-x(7-x) Cl1-xOx with Ln = Ce, Pr, Nd and x approximate to 0.2. Journal of Solid State Chemistry, 178 (4), 976-988. (doi:10.1016/j.jssc.2004.10.022).

Abstract

The isotypic oxonitridosilicate chlorides Ln(4)[Si4O3+xN7-x]Cl1-xOx with Ln = Ce, Pr, Nd and x approximate to 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 degrees C, using CsCl as a flux. The crystal structures were determined by single-crystal X-ray diffraction (P2(1)3, no. 198, Z = 4, Cc: a = 10.4461(12)pm, R1 = 0.0524; Pr: a = 10.3720(12)pm, R1 = 0.0415; Nd: a = 10.3618(12) pm, R1 = 0.0257) and found to be isotypic with Ce-4[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 Pr-4[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) mu(B)/Ce and 3.50(5) mu(B)/Pr, respectively. No magnetic ordering could be detected down to 2 K. The 4f(I) of cerium has been confirmed by XAS measurements.

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