Thermally stable and color-tunable bi-activated (Dy3+/Eu3+) alkaline earth metasilicate phosphor for luminescent devices

A solid-state reaction methodology has been adopted to synthesize Dy3+ (dysprosium)/Eu3+ (europium) co-activated Na4Ca4Si6O18 (NCMS) phosphors. The structural, morphological, and luminescence characteristics of the prepared materials have been investigated. The phase purity of the material was confirmed by X-ray diffraction (XRD) by comparing the diffraction peaks with the JCPDS standard pattern (JCPDS card no. 75-1687). The photoluminescence (PL) spectra of NCMS phosphors activated with Dy3+ and co-activated with Dy3+ (sensitizer)/Eu3+ (activator) ions were investigated. The as-prepared NCMS phosphors co-activated with Dy3+/Eu3+ ions were excited with near-ultraviolet light (λex = 348 nm) and showed the utmost energy transfer of up to 97.80% from sensitizer to activator. Dexter and Reisfeld's approximation specifically confirms that the energy transfer from sensitizer to activator was through electric dipole-dipole interactions. The Dy3+-activated NCMS phosphor showed an illumination shift from yellow to red by varying the Eu3+ ion concentration and colour tunability is also observed by altering the excitation energy. The emission intensity was sustained up to 92.21% at 423 K (∼150 °C), indicating an excellent thermal stability of the bi-activated NCMS phosphor. The Dy3+/Eu3+ co-doped NCMS phosphors display excellent thermal stability with flexible color tunability to emerge as promising contenders in the field of lighting and display technologies.