Na4La2−2xTb2x(CO3)5 nanophosphors: Hydrothermal synthesis and photoluminescence properties

Na 4 La 2−2 x Tb 2 x (CO 3 ) 5 ( x =0–0.5) nanophosphors were prepared via hydrothermal method , and the photoluminescence , concentration quenching, luminescence color chromaticity and thermal activation energy of samples were measured. The results indicate that samples with x values of 0–0.5 possess the pure monoclinic phase with an absorption edge at 250   nm. Na 4 La 2−2 x Tb 2 x (CO 3 ) 5 ( x =0–0.5) phosphors exhibit green luminescence, attributed to the 5 D 4 → 7 F J ( J =6, 5, 4, 3) transitions of Tb 3+ . The concentration quenching takes place at about x =0.3, but no decreased luminescence intensity is observed; moreover, the activation energy of thermal quenching of Na 4 LaTb(CO 3 ) 5 nanophosphor was calculated to be 0.116   eV. The luminescence properties of Na 4 La 2−2 x Tb 2 x (CO 3 ) 5 are benefited from its structural characteristics: long distance between Tb 3+ ions and the ordered distribution of Tb 3+ ions.