A significantly small I ω value and characteristic Voronoi index are found in the 8e and 4b sites with CN = 8 for Y in crystalline YBO 3 . From visual inspection, the Y coordination structure of the 8e and 4b sites in the YBO 3 crystal seems to be a square prismatic geometry rather than the square antiprism polyhedron corresponding to the reference model. Conversely, the polyhedral structure in crystalline LaBO 3 is understood to have a lower degree of spherical symmetry, as expected from the higher I ω value, even in ordered crystals. The degree of symmetry of the La coordination structure in the crystal is not much different from that of a-La50 glass. The novel ring structure consisting of three B 4 formed in the YBO 3 crystal, as shown in Fig. , can be achieved with a specially ordered structure including Y with square prismatic geometry.