Premium
Structure Evolution from Pb(Mg 1/3 Nb 2/3 )O 3 to La(Mg 2/3 Nb 1/3 )O 3
Author(s) -
Lin LiJiaun,
Wu TaiBor
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb04112.x
Subject(s) - perovskite (structure) , lanthanum , crystallography , crystal structure , superlattice , space group , lattice constant , materials science , x ray crystallography , solid solution , octahedron , diffraction , chemistry , mineralogy , inorganic chemistry , physics , metallurgy , optics , optoelectronics
The crystal structure of lanthanum‐modified lead magnesium niobates having composition (Pb 1− x La x ) (Mg (1+ x )/3 ‐Nb (2− x )/3 )O 3 with X = 0 to 1 was investigated by X‐ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B′ 1/2 ‐B″ 1/2 )O 3 ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.