Department of Materials Research and Physics, University of Salzburg, A-5020 Salzburg, Austria.
Inorg Chem. 2013 Jul 15;52(14):8005-9. doi: 10.1021/ic400589u. Epub 2013 Jun 21.
Nominal Li7La3Zr2O12 (LLZO) garnet, doped with (57)Fe2O3, was synthesized by sintering oxides and carbonates at T = 1100 °C in air. X-ray powder diffraction measurements show that Li(7-3x)Fe(3+)(x)La3Zr2O12 with x = 0.19 crystallizes in the cubic space group Ia-3d, with a0 = 12.986(4) Å at room temperature. SEM and electron microprobe measurements were made to obtain compositional information and check for the presence of phases other than garnet. Inductively coupled plasma optical emission spectroscopy measurements were made to determine the Li content. (57)Fe Mössbauer spectra obtained at 295 and 80 K show that about 96% of the total iron occurs as Fe(3+) and 4% as Fe(2+). Roughly two-thirds of the Fe(3+) cations are assigned to the tetrahedral site (24d) and roughly one-quarter to a highly distorted site (possibly at 96h) in the garnet structure. Smaller amounts of Fe(3+) and Fe(2+), around 5% each, occur at other crystallographic sites. On the basis of published (27)Al MAS NMR results and analysis of the (57)Fe Mössbauer spectra, it appears that at low concentrations Al(3+) and Fe(3+) substitute in Li7La3Zr2O12 in a similar manner. The aliovalent substitution Al(3+)/Fe(3+) ↔ 3Li(+) in LLZO stabilizes the cubic phase and also probably promotes its high Li-ion conductivity.
名义上的 Li7La3Zr2O12（LLZO）石榴石，掺杂（57）Fe2O3，是通过在空气中于 T = 1100°C 将氧化物和碳酸盐烧结合成的。X 射线粉末衍射测量表明，Li(7-3x)Fe(3+)(x)La3Zr2O12 与 x = 0.19 在室温下结晶为立方空间群 Ia-3d，a0 = 12.986(4)Å。SEM 和电子探针测量用于获得组成信息并检查是否存在除石榴石以外的其他相。电感耦合等离子体光学发射光谱测量用于确定 Li 的含量。在 295 和 80 K 下获得的（57）Fe Mössbauer 谱表明，大约 96%的总铁以 Fe(3+)和 4%以 Fe(2+)形式存在。大约三分之二的 Fe(3+)阳离子被分配到四面体位置（24d），大约四分之一分配到石榴石结构中的高度扭曲位置（可能在 96h）。石榴石结构中其他晶位上的 Fe(3+)和 Fe(2+)含量较小，约各占 5%。根据已发表的（27）Al MAS NMR 结果和（57）Fe Mössbauer 谱的分析，似乎在低浓度下，Al(3+)和 Fe(3+)以相似的方式替代 Li7La3Zr2O12 中的 Li(+)。LLZO 中的等价取代 Al(3+)/Fe(3+)↔3Li(+)稳定了立方相，也可能促进了其高锂离子电导率。
