Luminescence of Pb²⁺ Centers in SrS and SrSe Phosphors

Abstract

The emission and excitation spectra of the SrS: Pb 2+ and SrSe: Pb 2+ phosphors were measured at low temperatures. The 3 A 1u → 1 A 1g emission band at 374 or 392 nm is observed at 80 K in addition to the 3 T 1u → 1 A 1g emission band at 368 or 383 nm for SrS: Pb 2+ or SrSe: Pb 2+ , respectively. On these emission bands, phonon structures appear at 6 K. The zero-phonon line on the 3 A 1u → 1 A 1g emission band grows under the external magnetic field. The sharp excitation band observed at 351 nm for SrS: Pb 2+ or at 368 nm for SrSe: Pb 2+ at 80 K is assigned to the A band in the isolated Pb 2+ center. The excitation mechanism in the high energy region is explained as the transfer of the excitation energy from the host crystal to an unexcited Pb 2+ ion. It is confirmed that the rigid rotator model which explains admixture between the 3 T 1u and 3 A 1u states is also available for the complex Pb 2+ (S 2- ) 6 or Pb 2+ (Se 2- ) 6 in these phosphors.