The influence of polar order on the photoluminescence of Eu:BaZrxTi1-xO3 ceramics

The ability to tune and enhance the properties of luminescent materials (phosphors) is essential for optimizing the performance of devices and understanding the luminescence mechanisms. Eu3+ was used as a local structural probe for studying the impact of ferroelectric order and, more generally, of polar order on the photoluminescence of the model BaZrxTi1-xO3 perovskite (x = 0-1). The polar order evolves from long-range order typical of classic ferroelectrics (x = 0-0.15), via a diffuse transition behaviour (x = 0.15-0.25), to short-range order typical of relaxors (x >= 0.25) until the paraelectric state of BaZrO3 is achieved. The cooperative polar interactions existing in the lattice (x < 1) promote the off-centre displacement of Eu3+ determining a change of the lanthanide site symmetry and, consequently, an abrupt variation of the photoluminescence emission with temperature.