White emitting Ca2Tb8(SiO4)6O2:Eu2+/Eu3+ phosphors: Photoluminescence and efficient energy transfer

Highlights: • Ca₂Tb₈(SiO₄)₆O₂:Eu²⁺/Eu³⁺ phosphors were prepared by solid-state route. • The structural/elemental analyses indicate the formation of pure phase. • The excitation spectroscopy is explained by Tb³⁺-Eu³⁺ energy transfer. • Upon UV excitations it showed tunable color emission including white light. • The phosphor shows excellent thermal stability and suitable for UV-LEDs. Ca₂Tb₈(SiO₄)₆O₂:Eu²⁺/Eu³⁺ phosphors were prepared via solid-state diffusion route in reducing ambience. The structural/elemental analyses indicate the formation of pure phase which accommodates both Eu²⁺/Eu³⁺ ions. The shift of Tb³⁺ excitation band from 238 to 295 nm and increase (1.3×) in excitation intensity with Eu concentration in Ca₂Tb₈(SiO₄)₆O₂:Eu²⁺/Eu³⁺ phosphor is explained on the basis of Tb³⁺ to Eu³⁺ energy transfer. Upon various UV excitations (238−380 nm), Ca₂Tb₈(SiO₄)₆O₂:Eu²⁺/Eu³⁺ showed tunable color emission including warm white light. Moreover, the emission intensity only decreased 15% after increasing the temperature to 200 °C, revealing that present phosphors can be suitable for UV-LEDs.