Novel red-emitting garnet Na2CaTi2Ge3O12:Pr3+,Na+ phosphors

Abstract

A series of red-emitting garnet Na₂CaTi₂Ge₃O₁₂:Pr³⁺,Na⁺ phosphors were synthesized by a high-temperature solid-state reaction. The crystal structure, luminescence properties, decay lifetime, and thermal stability were initially studied. The excitation spectra show one broad band centered at 337 nm and several sharp bands centered at 451, 462, 474 and 488 nm, which are ascribed to the 4f² → 4f¹5d¹ and 4f² → 4f² transitions of Pr³⁺. The emission spectra show narrow band emissions centered at 595, 609, 622 and 630 nm, which correspond to the parity-forbidden intra-configuration 4f² → 4f² transitions of the Pr³⁺ ion. The optimum concentration of Pr³⁺ in Na₂CaTi₂Ge₃O₁₂:Pr³⁺,Na⁺ was determined to be 2 mol%. Upon excitation at 451 nm, the Na₂CaTi₂Ge₃O₁₂:Pr³⁺,Na⁺ phosphors exhibit an intense red emission at 609 nm with CIE chromaticity coordinates of (0.6524, 0.3457). The wider color gamut of the as-synthesized Na₂CaTi₂Ge₃O₁₂:Pr³⁺,Na⁺ is much higher than that of commercially available materials, such as CaSi₅N₈:Eu²⁺ and CaAlSiN₃:Eu²⁺. The results indicate that the novel red-emitting phosphors could be a potential candidate for display applications.