Structured diffuse scattering, local crystal chemistry and metal ion ordering in the (1-x)MgS center dot(x)/3Yb2S3, 0 <= x <= 0.45, 'defect' NaCl system

摘要

Rare earth sulfide solid solutions of 'defect' NaCl average structure type exhibit excellent colour characteristics and thus represent good prospects for use in the paints and plastics industry. As the colour characteristics of such systems are closely related to the local distribution of rare earth ions, it is important to know as much as possible about the latter. In this contribution, the reciprocal space shape of a highly structured, diffuse intensity distribution observed in a (1-x)MgS center dot xYb(2)/S-3, x = 0.30, sample is used to show that the smallest polyhedral building blocks of the average NaCl structure type should each have, as far as possible, the same composition as the overall macroscopic composition. Local crystal chemical considerations suggest that both the Yb3+ ions and the vacancies square would prefer to be opposite Mg2+ ions.