Synthesis and in situ ion irradiation of A-site deficient zirconate perovskite ceramics

Abstract

The influence of A-site vacancies on zirconate perovskite structured ceramics of formula A_1−xLa_2x/3ZrO₃ (A = Ca, Sr, Ba) has been investigated using 400 keV Kr⁺in situ ion irradiation in a TEM with varied temperature from 100 K to 673 K. The solubility limit of La within the Ba_1−xLa_2x/3ZrO₃ system was 5.33 ml% (x = 0.08) using a solid-state synthesis route, with space group symmetry of Pmm for x ≤ 0.08. The Ca_0.9La_0.067ZrO₃ and Sr_0.9La_0.067ZrO₃ samples were found to synthesise single-phase with the Pcmn and Pbnm symmetries of their respective end member structures. The addition of 6.67 ml% La (x = 0.1) in CaZrO₃ and SrZrO₃ was found to decrease the critical temperature of amorphisation, T_c, in comparison with the undoped structures. A similar decrease was found for the 5.33 ml% La doped BaZrO₃ structure. Namely, values were observed for doped samples of ≈404 K, ≈520 K and ≈621 K (A = Sr, Ca, Ba respectively), compared to ≈440 K, ≈623 K and ≈675 K for SrZrO₃, CaZrO₃ and BaZrO₃, respectively. This follows similar behaviour to that observed in titanate systems at low dopant levels, and these findings have been discussed in relation to both the presence of cation vacancies in the doped samples and the presence of the La cation. Void formation, growth and induced morphology changes have also been characterised, onset by ion irradiation.