Color tunability, concentration dependence, and temperature responsive afterglow of SrZn₂(PO₄)₂: Eu²⁺, Mn²⁺ phosphors

Long persistent luminescence (LPL) materials with color adjustable afterglow have a wide application prospect in display and information encryption, yet there are few reports on such materials. In this paper, SrZn₂(PO₄)₂ phosphors with tunable and thermal stimuli-responsive afterglow emissions were synthesized by a solid-state method. After ultraviolet (UV) excitation, the prepared samples exhibited emission at 419 nm, 533 nm, and 633 nm due to Eu²⁺: 4f⁶5d¹ → 4f⁷ transitions, Mn²⁺: ⁴T₂(⁴G) →⁶A₁(⁶S) transitions, and Mn²⁺: ⁴T₁(⁴G) → ⁶A₁(⁶S) transitions, respectively. The Commission Internationale de I' Eclairage (CIE) coordinates of samples can be changed among blue, white, and yellow by varying the Mn²⁺ concentration. Additionally, due to the differing thermal stability of Eu²⁺ and Mn²⁺, the phosphor exhibited a temperature-responsive afterglow, and its colors can be adjusted between white and yellow over a temperature range from 293 K to 383 K. Given its distinctive temperature-responsive afterglow, the prepared phosphor is suitable for use as a temperature sensor. Moreover, the tunable afterglow colors of the phosphors are advantageous for application in anti-counterfeiting.