“…The reasons for the enhancement of the PL intensity can be ascribe to the change of the lattice symmetry. The change of the lattice symmetry will give rise to a remarkable effect on the properties of Pr 3+ and further influence the luminescence properties [31][32][33][34], when Ca 2+ (1.34Å, 12 CN) ions are replaced by bigger radius Sr 2+ ions (1.44Å, 12 CN), the symmetry of the pseudoperovskite units was changed [33]. As previously discussed Pr 3+ ions dispersed in the pseudo-perovskite units of samples' crystal structure.…”