The structure of Li0.43Na0.36CoO1.96 using neutron powder diffraction

Topotactic Routes to Layered Calcium Cobalt Oxides

“…Consequently, samples were analyzed by total mass loss and no attempts were made to characterize the decomposition pathways. In the instances of Ca CoO (P2) and Ca CoO (P2), which are both derived from the Na CoO (P2) precursor, we considered the possibility of oxygen nonstoichiometry since some accounts of the synthesis of Na CoO report oxygen deficiency (30)(31)(32). The TGA results of the Ca V CoO products, however, showed no evidence of weight gain when analyzed under flowing oxygen.…”

Studies on Formation and Decomposition of the Layered Cobaltite LixNayCoO2

“…Stoichiometric amounts of LiCoO 2 and γ-Na 0.7 CoO 2 were mixed thoroughly in an agate mortar, pressed into a pellet, annealed at 1050 • C for 6 hours in oxygen flow, and then quenched onto a thick copper plate. According to X-ray analysis, the obtained sample had a structure identical to that described in [28] and did not contain The contents of alkaline elements determined by ICP-AES analysis were found to be 2.86 and 8.10 wt% for Li and Na, respectively. This allowed us to write the formula of the lithium-sodium mixed cobaltite as Li 0.42 Na 0.36 CoO 2 .…”

“…However, no solid solutions were found to exist in the LiCoO 2 -Na x CoO 2 system [27]. At the same time, an ordered phase with a layered structure (Li 0.43 Na 0.36 CoO 1.96 ) was reported [28] to form in the region close to the equiatomic alkaline ions concentration. The structure of this phase was attributed to the P6 3 mc space group with hexagonal lattice parameters a = 2.839 (4) and c = 20.36(3)Å and the ABCAACBA packing of oxygen layers.…”

“…It is essential that lithium and sodium ions are not mixed but occupy separate planes between CoO 2 layers. Here, Li ions have an octahedral environment, while sodium ions are in the trigonal prisms [28]. This ordered phase is a good thermoelectric material indeed [29].…”

“…In addition, effects of magnetic ordering were observed [30] at T < 100 K. However, despite the promising properties of the ordered lithium-sodium cobaltite, there are only few works [27][28][29][30][31][32][33] devoted to this phase. The reason is that the double cobaltite is difficult to synthesize because it is thermodynamically stable only at T > 1000 • C [28]. The purpose of the present work is to study the peculiarities of formation and decomposition of the ordered lithiumsodium cobaltite "Li 0.5 Na 0.5 CoO 2 ."…”