Effects of A-site doping on microstructure and phase separation of La0.5RE0.2Sr0.3MnO3 (RE=Eu, Ho, Yb, Lu)

Phase separation and microstructure of La0.7Sr0.3MnO3 doped with rare earth elements (Eu, Ho, Yb and Lu) are studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition and diffraction analyses demonstrate that the ionic radius of doping element plays an important role in the crystalline structure and the lattice constants of the secondary phase. When La3+ is replaced partly by Eu3+ or Ho3+, orthorhombic perovskite structure with space group Pnma is formed due to the distortion of MnO6 octahedra. Different from the phenomenon observed by Huang et al., however, the hexagonal non-perovskite structure (YbMnO3 and LuMnO3) has appeared when La3+ and Sr2+ are substituted completely by Lu3+ or Yb3+.