Alkali ions effect on optical properties of Tm3+, Yb3+ co-doped gadolinium tungstate phosphor

Highlights: • The Tm³⁺, Yb³⁺ co-doped gadolinium tungstate phosphors have been synthesized through solid state reaction method. • The structural analyses confirm the formation of two monoclinic crystalline phases. • The phase fraction varies on addition of Li⁺, Na⁺ and K⁺ alkali ions. • It gives intense emissions centered at 472 and 793 nm due to Tm³⁺ on excitation with 976 nm. • When the alkali ions are added in phosphor, the emission intensity of bands are enhanced significantly.