The determination of an unknown oxygen atomposition in rare-earth zirconate pyrochlores by a 111 systematic-row convergent-beam electron diffraction technique

A focused probe systematic-row large angle convergent-beam electron diffraction (CBED) technique has been used to determine an unknown oxygen atom fractional coordinate in two rare-earth zirconate pyrochlores La2Zr2O7 and Sm2Zr2O7 to an estimated accuracy of better than 0.005. The bond valence method suggests that the CBED-determined x values are chemically plausible. The simplicity of the CBED technique used suggests that it may be a very useful technique for determining positions of light atoms in the presence of strongly scattering heavy-metal atoms.