Anion Ordering in Fluorinated La2CuO4

HREM Study of Fluorinated Nd2CuO4

“…1). Recently we showed that the soft #uorine insertion into La CuO and LaHo Sr CuO (T* type structure) results in anion rearrangements between the two possible positions in the R O blocks, creating numerous structures which can be considered as intermediate ones between T and T types (11,12). The highly #uorinated La CuO F phase exhibits an ordered alternation of #uorite-type and rock-salttype slabs, not only along the c-axis but also within the ab-plane.…”

“…The highly #uorinated La CuO F phase exhibits an ordered alternation of #uorite-type and rock-salttype slabs, not only along the c-axis but also within the ab-plane. As a result the octahedral coordination of some of the Cu ions is transformed into a square pyramidal one (11). The formation of a monoclinic superstructure in the #uor-inated LaHo Sr CuO is accompanied by an equal anion arrangement within the initially di!erent #uorite and rock salt blocks (12).…”

Suppression of Modulations in Fluorinated Bi-2201 Phases

“…The inner walls of the Cu tube, which is used as a reaction vessel, adsorb the released oxygen. Usually both kinds of anion exchange reactions occur simultaneously at high temperatures (350}5003C), while at low temperatures (150}3003C) the insertion process dominates (5,17). The #uorination of the Bi-2201 phase appears to follow the anion exchange reaction, even if the #uorination temperature is rather low (150}2003C).…”

“…In contrast to the anion exchange of F\ for O\, which reduces the copper oxidation state, #uorine intercalation on the interstitial site leads to the oxidation of the conducting (CuO ) planes and, in several cases, to structural transformations (5,6,17). It is of interest to examine the possibility of further oxidation of the Bi-based cuprates by #uorination and to study its e!ect on ¹ .…”

“…Fluorination was successfully explored for oxidizing di!erent cuprates, and several new superconducting compounds were prepared (5,6). In contrast to the anion exchange of F\ for O\, which reduces the copper oxidation state, #uorine intercalation on the interstitial site leads to the oxidation of the conducting (CuO ) planes and, in several cases, to structural transformations (5,6,17).…”