Enhanced piezoelectric properties and strong red luminescence in Pr-doped Bi0.5Na0.5TiO3–BaTiO3 multifunctional ceramics

Multifunctional ceramics with the 0.93(Na0.5Bi0.5)1-xPr3+xTiO3-0.07BaTiO3 (abbreviated as BNBT-xPr, x = 0.00, 0.002, 0.004, 0.006, 0.008) were synthesized using the solid-phase reaction method. This study systematically investigated the phase structure, microstructure, dielectric, ferroelectric, piezoelectric, and photoluminescence properties. As the value of x increased, the ceramics underwent a transition from a co-existing rhombohedral (R) and tetragonal (T) phases to a T phase with a slight R distortion. In addition, the grain size decreased, and the relative density increased. The Pr3+ doping led to a decrease in the coercive field and an improved reversible phase transition, accompanied by a reduction in the depolarization temperature (Td) from 91 °C to 41 °C. The ceramic with x = 0.006 showed excellent piezoelectric properties, with a d33 = 201 pC/N and kp = 30.6%. Such properties were ascribed to the appropriate R/T phase ratio, increased relative density, decreased coercive field, and improved reversible phase transition. Moreover, under excitation at 451 nm, the ceramics exhibited bright red emission bands at 611 nm and 655 nm, corresponding to the transitions of 1D2→3H5 and 3P0→3F2, respectively. After polarization, the relative intensity of the emission peak at 655 nm significantly increased due to the changed lattice environment caused by the electric field. These Pr-doped BNBT ceramics demonstrated great potential in applications requiring electro-optic integration and coupling devices as multifunctional materials.