Structural, electrical and optical properties of lanthanide-doped Na0·4K0·1Bi0·5TiO3 ceramics

Lead-free Sodium–Potassium Bismuth Titanate (Na_0·4K_0·1Bi_0·5TiO_3; NKBT) ceramics doped with rare earth elements (RE: Ho, Pr, Nd, Er, Dy) were synthesized using the solid-state reaction technique. The X-ray diffraction analysis showed that the RE-doped NKBT ceramics crystallize in a pure perovskite phase with R3c as the space group. Interestingly, the doped ceramics exhibited low dielectric losses compared to the undoped NKBT, especially in the high temperature region. The dielectric permittivity of the NKBT-Dy ceramic at high temperatures was treated using the temperature coefficient of capacitance (TCC ± 20% with ε_stable = 2451 in a wide temperature range of 150 °C–470 °C). In addition, all samples showed higher ferroelectric polarization comparing with pure NKBT. Furthermore, the incorporation of RE³⁺ ions into the NKBT host lattice led to the luminescence properties in the visible region under different excitation wavelengths. The simultaneous presence of ferroelectric/dielectric and photoluminescence properties makes NKBT-RE a promising candidate for optoelectronic applications.