The main goal of this work was to verify whether a phase with composition K₂CaSi₄O₁₀ exists in the ternary system K₂O‐CaO‐SiO₂. Therefore, a series of solid‐state reactions of stoichiometric mixtures of K₂CO₃, CaCO₃ and SiO₂ was performed at 800 and 900?C which, indeed, resulted in the formation of this previously unknown potassium calcium silicate. More detailed characterizations of this compound were based on single‐crystal X‐ray diffraction experiments. Basic crystallographic data are as follows: triclinic symmetry, space group P‐1, a = 7.0915(7) Å, b = 8.4211(9) Å, c = 10.2779(12) Å, α = 104.491(10)°, β = 100.570(9)°, γ = 113.738(9)°, V = 515.26(10) ų, Z = 2. Structure solution was performed by direct methods. Subsequent refinement calculations using anisotropic displacement parameters for all atoms converged to a residual of R(|F|) = 0.0355 for 1889 independent reflections with I > 2σ(I). From a structural point of view K₂CaSi₄O₁₀ belongs to the so‐called litidionite family of A′AMSi₄O₁₀ compounds for which several natural and synthetic representatives have been described in the literature. Actually, it is the first member where the A′‐ and A‐positions are exclusively occupied by K‐ions. Following the nomenclature for oxosilicates K₂CaSi₄O₁₀ can be allocated to the group of the tubular chain silicates. Fundamental building units are loop‐branched dreier double chains (running parallel to [100]) which can be described using the following structural formula: {lB,}[³Si₈O₂₀]. Ca‐ions are coordinated by 5 nearest oxygen neighbors in form of distorted trigonal bipyramids. By sharing a common edge two adjacent bipyramids are linked into [Ca₂O₈]‐dimers providing linkage between consecutive tubes in the direction of the c‐axis. Charge compensation is achieved by the incorporation of the larger potassium ions into cavities of the heteropolyhedral network. Powder X‐ray diffraction patterns of the bulk material of the synthesis products revealed that, additionally to K₂CaSi₄O₁₀, the 800°C ‐sample contained K₈CaSi₁₀O₂₅ and at least one further, yet unknown crystalline phase. This unidentified so‐called 22‐Å compound was also present in the 900 °C‐specimen together with K₂CaSi₄O₁₀ and K₂Ca₄Si₈O₂₁. Our proof of existence of K₂CaSi₄O₁₀ is a further step towards a better understanding of the ternary system K₂O‐CaO‐SiO₂ and provides a basis for identification and quantification of this compound in phase analysis. It corrects earlier phase‐analytical studies on this system which is of relevance for applied and technical mineralogy including different types of residual materials such as slags or ashes from biomass combustion. The results of our investigation show that even comparatively simple ternary oxide systems are not as well understood as expected.

中文翻译：

---

K2CaSi4O10：K2O-CaO-SiO2三元体系中的一个新相，并且是锂钛矿组的晶体结构的成员

这项工作的主要目的是验证三元体系K ₂ O-CaO-SiO _2中是否存在成分为K ₂ CaSi ₄ O ₁₀的相。因此，在800和900？C下进行了一系列K ₂ CO ₃，CaCO ₃和SiO ₂的化学计量混合物的固态反应，实际上导致了这种以前未知的硅酸钙钙的形成。该化合物的更详细的表征是基于单晶X射线衍射实验。基本晶体学数据如下：三斜对称，空间群P-1，a = 7.0915（7）Å，b = 8.4211（9）埃，c ^ = 10.2779（12）A，α= 104.491（10）°，β= 100.570（9）°，γ= 113.738（9）°，V = 515.26（10）一种³，ž＝ 2。通过直接方法进行结构求解。随后对所有原子收敛到残差R（| F |）= 0.0355的所有原子使用各向异性位移参数进行精化计算，计算1889年I >2σ（I）的独立反射。从结构的角度来看，K ₂ CaSi ₄ O ₁₀属于所谓的A'AMSi ₄ O ₁₀锂锰矿家族。文献中已经描述了几种天然和合成代表的化合物。实际上，它是第一个成员的A'和A-位置仅被K离子占据。以下为oxosilicates k中的命名法₂硅钙₄ ø ₁₀可以被分配给该组的管状链硅酸盐。基本建筑单元是环状分支的dreier双链（平行于[100]运行），可以使用以下结构式描述：{lB，} [ ³ Si ₈ O ₂₀]。钙离子由变形的三角双锥体以5个最近的氧邻域进行协调。通过共享公共边缘，将两个相邻的双锥体连接到[Ca ₂ O ₈ ]-二聚体中，从而在c轴方向的连续管之间建立连接。通过将较大的钾离子掺入杂多面体网络的空腔中，可以实现电荷补偿。合成产物散装材料的粉末X射线衍射图谱表明，除K ₂ CaSi ₄ O _10外，800°C样品中还包含K ₈ CaSi ₁₀ O ₂₅和至少一个另外的但未知的结晶相。在900°C的样品中还存在这种未知的所谓的22Å化合物，还包括K ₂ CaSi ₄ O ₁₀和K ₂ Ca ₄ Si ₈ O ₂₁。我们对K ₂ CaSi ₄ O ₁₀的存在的证明是迈向更好地理解三元体系K ₂ O-CaO-SiO ₂的又一步。并为在相分析中鉴定和定量该化合物提供了基础。它纠正了对该系统的早期阶段分析研究，该研究与应用和技术矿物学有关，包括不同类型的残留物质，例如生物质燃烧产生的炉渣或灰烬。我们的研究结果表明，即使相对简单的三元氧化物体系也没有像预期的那样被很好地理解。