In the course of a systematic study of a part of the quaternary system Fe₂O₃-CaO-Al₂O₃-MgO (FCAM) the previously unknown compound Ca_2.38Mg_2.09Fe³⁺_10.61Fe²⁺_1.59Al_9.33O₃₆ (FCAM-III) has been synthesized. By analogy with the so-called SFCA series [1–5], our investigation in the system of FCAM shows the existence of a stoichiometric homologous series M_14+6nO_20+8n, where M = Fe, Ca, Al, Mg and n = 1 or 2.

In air, we can prove the formation of coexisting FCAM-III and FCAM-I solid solutions at 1400 °C. By increasing the temperature up to 1425 °C FCAM-I disappears completely and FCAM-III co-exists with magnesiumferrite and a variety of calcium iron oxides. At 1450 °C FCAM-III breaks down to a mixture of FCAM-I again as well as magnesioferrite and melt. Small single-crystals of FCAM-III up to 35 µm in size could be retrieved from the 1425 °C experiment and were subsequently characterized using electron microprobe analysis and synchroton X-ray single-crystal diffraction. Finally the Fe²⁺/Fe_tot ratio was calculated from the total iron content based on the crystal-chemical formula obtained from EMPA measurements and charge balance considerations. FCAM-III or Ca_2.38Mg_2.09Fe³⁺_10.61Fe²⁺_1.59Al_9.33O₃₆ has a triclinic crystal structure (space group P $\bar{1}$). The basic crystallographic data are: a = 10.223(22) Å, b = 10.316(21) Å, c = 14.203(15) Å, α = 93.473(50)°, β = 107.418(67)°, γ = 109.646(60)°, V = 1323.85(2) ų, Z = 1.

Using Schreinemaker's technique to analyze the phase relations in the system Fe₂O₃-CaO-Al₂O₃-MgO it was possible to obtain the semi-quantitative stability relations between the participating phases and construct a topologically correct phase sequence as a function of T and fO₂. The analysis shows that Ca₂Al_0.5Fe_1.5O₅ (C₂A_0.25F_0.75) and CaAl_1.5Fe_2.5O₇ (CA_0.75F_1.25) with higher calculated Fe²⁺ contents are preferably formed at lower oxygen fugacity and react to CaAl_0.5Fe_1.5O₄ (CA_0.25F_0.75) by increasing fO₂. Spinel-type magnesium-aluminium-ferrite (Mg,Fe²⁺)Fe³⁺_1.25Al_0.75O₄ or (MA_0.375F_0.625) is the typical phase which occurs at high temperature (1400 °C).

在对部分四元体系Fe ₂ O ₃ -CaO-Al ₂ O ₃ -MgO（FCAM）进行系统研究的过程中，先前未知的化合物Ca _2.38 Mg _2.09 Fe ³⁺ _10.61 Fe ²⁺ _1.59 Al _9.33 O ₃₆（FCAM-III）已经合成。通过类似于所谓的SFCA系列[1-5]，我们在FCAM系统中的研究表明存在化学计量的同源序列M _{14 + 6n} O _{20 + 8n}，其中M = Fe，Ca，Al，Mg和n = 1或2。

在空气中，我们可以证明在1400  °C下共存的FCAM-III和FCAM-I固溶体的形成。通过将温度升高至1425  °C，FCAM-I完全消失，FCAM-III与亚铁酸镁和多种钙铁氧化物共存。在1450  °C时，FCAM-III再次分解为FCAM-I的混合物，以及镁铁矿和熔体。 可以从1425  °C实验中回收尺寸最大为35 µm的FCAM-III小单晶，随后使用电子微探针分析和同步X射线单晶衍射进行表征。最后是Fe ²⁺ / Fe _tot根据总铁含量，根据从EMPA测量获得的晶体化学公式和电荷平衡考虑因素，计算出铁的比例。FCAM-III或Ca _2.38 Mg _2.09 Fe ³⁺ _10.61 Fe ²⁺ _1.59 Al _9.33 O ₃₆具有三斜晶体结构（空间群P $\overline{\mathrm{1个}}$）。基本晶体学数据为：a = 10.223（22）Å，b = 10.316（21）Å，c = 14.203（15）Å，α= 93.473（50）°，β= 107.418（67）°，γ= 109.646（ 60）°，V = 1323.85（2）ų，Z = 1。

使用Schreinemaker的技术分析Fe ₂ O ₃ -CaO-Al ₂ O ₃ -MgO系统中的相关系，可以获得参与相之间的半定量稳定性关系，并构造一个拓扑正确的相序作为函数。T和f O ₂。分析表明，Ca ₂ Al _0.5 Fe _1.5 O ₅（C ₂ A _0.25 F _0.75）和CaAl _1.5 Fe _2.5 O ₇（CA _0.75 F _1.25优选地，在较低的氧逸度下形成具有较高计算的Fe ²⁺含量的Fe ²⁺），并通过增加f O ₂与CaAl _0.5 Fe _1.5 O ₄（CA _0.25 F _0.75）反应。尖晶石型镁铝铁氧体（Mg，Fe ²⁺）Fe ³⁺ _1.25 Al _0.75 O ₄或（MA _0.375 F _0.625）是在高温（1400 °C）下出现的典型相。