Evidence for a New Monoclinic Bi–La Oxide Solid Solution: Identification and Structural Relationship to the Rhombohedral Bi–Sr–O Type

Ab Initio Determination of Bi4.86La1.14O9 Monoclinic Structure from Powder Neutron Diffraction Data. Characterization of the Related Solid Solution

“…All DTA curves were similar to the thermogram presented recently for the Bi La O material (15). After a broad exothermal e!ect corresponding to the formation of the phase, two endothermal peaks relative to P and P were evidenced.…”

“…The recent study of the Bi La O sample, for which the monoclinic phase was evidenced (15), has shown that the preparation of a pure quenched form of is the "rst necessary step for the monoclinic preparation. The X-ray di!raction diagrams of samples quenched in liquid nitrogen from 8003C have been indexed with the re#ections setting of the / -type hexagonal cell.…”

“…Complementary to the qualitative Guinier LenneH study of Bi La O previously presented (15), an X-ray thermodi!ractometry investigation of this sample has been realized using a Siemens D5000 di!ractometer in order to determine the evolution of the cell parameters. The X-ray diagrams were recorded at 273C and from 50 to 7503C (step 253C) during isothermal treatments, and in each case, the lattice constants were re"ned from the same series of 21 re#ections, using a least-squares method.…”

“…For each composition examined, a fraction of the sample initially quenched in liquid nitrogen was subsequently annealed at 3003C for 2 to 3 days, taking into account the synthesis process of the -Bi La O monoclinic form as previously described (15).…”

“…Bi La O is a term of a wide Bi \V La V O solid solution domain, with 0.154x40.333, which exhibits anomalies in the evolution of the cell parameters versus composition (14); for one of the particular compositions (15). This paper deals with the ab initio structure determination of this new phase from powder neutron di!raction data; identi"cation and investigation of the corresponding solid solution, using various techniques such as X-ray di!ractometry (at ambient pressure and versus the temperature), dilatometry, impedance spectrometry, and thermal analyses (DTA), are also presented.…”