Evolution of the crystal structure of RVO3 (R = La, Ce, Pr, Nd, Tb, Ho, Er, Tm, Yb, Lu, Y) perovskites from neutron powder diffraction data.
RVO3 perovskites have been prepared in the widest range of R (3+) ionic size, from LaVO3 to LuVO3. Pure polycrystalline samples have been obtained by a citrate technique leading to reactive RVO4 precursors, followed by thermal treatments in a reducing H2/N2 (15/85%) flow to stabilize V(3+) cations. These oxides have been studied at room temperature by high-resolution neutron powder diffraction to follow the evolution of the crystal structures along the series. The distortion of the orthorhombic perovskite (space group Pbnm), characterized by the tilting angle of the VO6 octahedra, progressively increases from La to Lu due to simple steric factors. Additionally, all of the perovskites show a subtle distortion of the VO6 octahedra which significantly increases from La to Tb, and then slightly decreases for the last terms of the series. The stability of the crystal structure is also discussed in light of bond-valence arguments.
Martínez-Lope
M J
MJ
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid, Spain.
Alonso
J A
JA
Retuerto
M
M
Fernández-Díaz
M T
MT