Polycrystalline Ca₂Fe_2-xGa_xO₅ brownmillerite samples of nominal x = 0.5, 0.7, 0.9 and 1 compositions have been synthesized by solid state reaction under normal pressure conditions. Whatever x is, room temperature structural analyses by Rietveld refinements and electron microscopy techniques highlight a centrosymmetric Pnma space group. Furthermore, STEM-HAADF observations point towards a preferential Ga occupation at the tetrahedral sites of the structure in agreement with the Rietveld analyses. This structure remains unchanged up to 1000 K as shown by thermo-diffraction analysis. As the Ga content x increases, the room temperature unit cell volume decreases gradually consistently with the fourfold coordination of the smallest Ga³⁺ ionic radius than that of high spin Fe³⁺ in the same tetrahedral coordination. This magnetic dilution by a diamagnetic cation is responsible for the T_N decrease revealed by magnetization measurements and allows a spin flop transition to be observed. Despite their similarities with the Ca₂Fe_2-xAl_xO₅ samples, no electric polarization could be evidenced for the homologous Ca₂Fe_2-xGa_xO₅ series.

标称x  = 0.5、0.7、0.9和1组成的多晶Ca ₂ Fe _{2- x} Ga _x O ₅褐锰矿样品是通过在常压条件下进行固相反应合成的。无论x是多少，通过Rietveld改进和电子显微镜技术进行的室温结构分析都强调了中心对称的Pnma空间群。此外，STEM-HAADF观测结果表明，与Rietveld分析相一致，该结构的四面体位点优先存在Ga占据。如热衍射分析所示，该结构在高达1000 K的范围内保持不变。随着Ga含量x的增加，在相同的四面体配位下，与最小自旋Fe ³⁺相比，最小的Ga ³⁺离子半径的四重配位，使室温晶胞体积逐渐减小。反磁性阳离子的这种磁性稀释是磁化测量所揭示的T _N降低的原因，并且可以观察到自旋翻转转变。尽管与Ca ₂ Fe _{2- x}相似对于Al _x O ₅样品，对于同源Ca ₂ Fe _{2- x} Ga _x O ₅系列，没有极化迹象。