Structures and phase diagram for the system CaTiO3-La2/3TiO3

Abstract

High-resolution neutron and synchrotron X-ray powder diffraction have been used to examine various compositions across the system (1−x)CaTiO3−xLa2/3TiO3. The structures at room temperature were determined according to composition: in Pbnm for 0≤x≤0.5, Ibmm for 0.5<x<0.7, then I4/mcm for 0.7x≤0.9, and finally in Cmmm for x≥0.9. Although the four structures are the same as those proposed previously in an X-ray diffraction study, the phase boundaries are somewhat different, in particular the Pbnm↔Ibmm phase boundary has been extended from x≤0.4 to x>0.5 in the current study based on our high-resolution neutron diffraction data. From in situ measurements to identify structures above room temperature, an approximate composition–temperature phase diagram has been constructed, involving four temperature-induced phase transitions: Pbnm→I4/mcm, Ibmm→I4/mcm, I4/mcm→Pm3¯m and Cmmm→P4/mmm. © 2007, Elsevier Ltd.