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Compounds in a CaO–Y2O3–SnO2 system were prepared by a solid‐state reaction at 1673 K. The phase relation in this system was investigated by powder X‐ray diffraction. Besides the previously reported ternary compounds, CaSnO3, Ca2SnO4, Y2Sn2O7, and a quaternary compound Ca0.4Y1.2Sn0.4O3, solid‐solution series of Ca2−xY2xSn1−xO4 with 0≤x≤0.5, and Ca1−yY2ySn1−yO3 with 0≤y≤0.2 and 0.95≤y≤1.0 were found. The cell parameters of these solid‐solution series were refined. The changes of rhombohedral cell parameters in the samples prepared in the range 0.565

A new quaternary oxide, calcium yttrium stannate, Ca(0.8)Y(2.4)Sn(0.8)O(6), is isostructural with Mg(3)TeO(6) (trigonal, R-3). The empirical formula can be expressed as (Ca(0.2667)Y(0.7333))(6)(Y(0.4)Sn(0.6))SnO(12). The Ca/Y site has a distorted coordination octahedron of O atoms, with Ca/Y-O distances ranging from 2.227 (3) to 2.350 (3) Angstrom, while the octahedra of O atoms that coordinate to the Sn and Y/Sn sites are nearly regular, with an Sn-O distance of 2.066 (2) Angstrom and a Y/Sn-O distance of 2.147 (3) Angstrom.

A new quaternary compound in the Ca-Eu-Sn-O system, namely calcium europium tin heptaoxide, Ca1.5 Eu3Sn0.5 O7, was prepared by solid-state reaction at 2073 K. All atoms in the structure are on 4i special positions (on mirrors) in space group C2/m. Ca/Eu sites are situated within two O octahedra and within two sevenfold coordination sites surrounded by O-capped trigonal prisms. A Ca/Eu/Sn site is coordinated by five O atoms. The structural formula can be represented as (Ca0.28 Eu0.72)(Ca0.16 Eu0.84)(Ca0.46 Eu0.54)(Ca0.28 Eu0.72)(Ca0.32 Eu0.18 Sn0.50)O7. The crystal structure is a new type and is related to the structure of B-form Eu2O3.

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