H. Drache et al., Evidence for a new monoclinic Bi-La oxide solid solution: Identification and structural relationship to the rhombohedral Bi-Sr-O type, J SOL ST CH, 151(2), 2000, pp. 281-285
As a term of the Bi-Sr-O rhombohedral type Bi1-yLayO1.5 solid solution, the
Bi17La4O31.5 mixed oxide (y no, 0.19) has been investigated, Air-quenching
from the high temperature domain of the beta(1) disordered form allows one
to preserve at room temperature a metastable form of beta(1). This form tr
ansforms exothermally on heating near 200 degrees C to a new monoclinic pha
se. This transformation and the transition monoclinic phase --> stable orde
red rhombohedral beta(2), which occurs at 445 degrees C, are both irreversi
ble on cooling for this composition. The beta(2) --> beta(1) transition occ
urs reversibly near 660 degrees C, under usual dynamic conditions (300 degr
ees h(-1)). The monoclinic cell lattice constants, a = 9.492(2), b = 7.951(
2), c = 7.028(2) Angstrom, beta = 104.74(1)degrees, lead to Z = 12 for the
unit formula Bi0.81La0.19O1.5 and imply a disordered cationic sublattice. T
his mixed oxide appears as a term of a new variety of a aide solid solution
(that will name epsilon hereafter). (C) 2000 Academic Press.