The EPR of Ce3+ in congruent SrXBa1-xNb2O6 (x = 0.61) is characterized by t
he orthorhombic g-tensor {0.89, 3.55, 0.54} with principal axes lying in th
e c-plane, tilted with respect to the a- and b-axes by 21.1 degrees: and al
ong the c-axis. Ce3+ occupies a single crystallographic site in the crystal
, leading to a unique EPR spectrum. The point symmetry of the Ce3+ position
, C-1, is lower than that of the replaced alkaline-earth ions, C-4 or C-s.
This is attributed to an off-centre movement of Ce3+. The Ce3+ signal decre
ases under illumination. No further EPR signal is detected to arise from th
e photoionization of Ce3+.