Enhancing luminescence and dielectric properties in ceramics: rare-earth modification of KMg₄(PO₄)₃-based materials

In order to improve the resource value of phosphates by developing smart or multifunctional materials for a variety of applications, we have successfully synthesized rare-earth element (RE³⁺)-doped pure polyphosphate materials, designated by the chemical formula KMg₄(PO₄)₃, by the high-temperature solid-solution method. The resulting pure phases are crystallized in the Pnnm orthorhombic system. Analysis by X-ray diffraction (XRD) and infrared spectroscopy (IR) confirmed the high purity of the phases and the incorporation of lanthanide elements into the crystal structure, demonstrating both structural completeness and high thermal stability. Optical properties analysis reveals that they are promising materials for light-emitting diode (LEDs) applications because of their broad absorption bands ranging from UV to near-IR. Their emission covers the visible spectrum as well as exhibiting short luminescence decay times. (τ = 1.31 ms for Dy³⁺ ions and τ = 0.41 ms for Nd³⁺ ions). In parallel, the electrical properties demonstrated ionic conductivity at intermediate temperatures. Ionic conduction is enhanced by trivalent doping, as the material doped with Nd³⁺ presents the highest conductivity value at room temperature (σ = 2.85*10^–11 S.cm⁻¹). The dielectric properties confirm their potential use as positive electrode materials for battery technology.