“…The crystal structure of Eu x TaO 3 (shown in Figure 1b) is similar to that of a double perovskite, [
31–33 ] which has a unit cell composed of two formula units of ABO 3 along the crystalline c ‐axis. However, Eu x TaO 3 alternates between an unoccupied A site and an Eu A site with partial occupancy 2 x , [
32,34,35 ] hence we name this structure a fractional perovskite. The partial Eu site occupancy results in slight distortions of the two TaO 3 octahedra along the a and b axes, causing oxygen ions at
to shift more significantly along c compared to those at
.…”