Synthesis of a new orthorhombic “SrLaMnO 4” phase with superstructure via complex precursors

Abstract

Solid solution of (Sr, La) 2MnO 4 with K 2NiF 4 structure was synthesized via decomposition process of organometallic complexes of constituent elements for the composition of La/Sr ratio >1. A new orthorhombic phase with a distorted oxygen octahedron appeared. The preparation under low oxygen partial pressure at high temperature was necessary to form this new orthorhombic phase. Some degree of defect in A-site (site for Sr or La) resulted in the formation of single phases of both tetragonal and orthorhombic compounds for La/Sr ratio >1. The lattice parameters of a new orthorhombic Sr 0.5La 1.3MnO 3.95 phase were a = 5.512(2), b = 5.4863(3) and c = 12.9295(7) Å with the space group Cmca (No. 64). The unit cell has a dimension with 2 a t × 2 a t × c t , where a t and c t are the lattice parameters of the fundamental body centered tetragonal cell of K 2NiF 4 structure with I4/ mmm space group. In this structure an oxygen octahedron is distorted and tilts each other by angle of 4.5°. This kind of orthorhombic distortion was first found in (Sr, La) 2MnO 4 solid solution.