Fundamental luminescence properties of Mn4+ activated Ca14Al10Zn6O35 phosphor

Abstract

Ca₁₄Al₁₀Zn₆O₃₅:Mn⁴⁺ (CAZO:Mn⁴⁺) is one of the few Mn-activated oxide phosphors with commercial application potential, owing to its strong absorption of near-UV and blue light, high quantum yield, and super-low thermal quenching effect. However, comprehensive studies on its fundamental luminescence properties are scarce. In this study, we determined the zero-phonon line (ZPL) energy of the excitation and emission states including ⁴T_2g, ²T_2g, ⁴T_1g,a, ⁴T_1g,b/CT, ²T_1g, and ²E_g, as well as the vibration energy of the frequency modes ν₁–ν₆ for the [MnO₆] octahedron in the CAZO host. When exploring the relationship between ZPL emission energy (E(²E_g)_ZPL) and Racah parameters (B and C), it was constructed as E(²E_g)_ZPL = 7B + 3.1C, which was proved universal for Mn⁴⁺-activated phosphors. Besides, we studied the mechanisms for concentration quenching and thermal quenching of the CAZO:Mn⁴⁺ phosphor. The concentration quenching arises mainly from the direct energy transfer from Mn⁴⁺ ions to the adjacent quenching sites, rather than the most common multi-polar interaction in other Mn⁴⁺-activated phosphors. This means that high-concentration doping and high QY can be simultaneously achieved by decreasing the crystal defects of the CAZO:Mn⁴⁺ phosphor, which is of great significance for industrial application. On the other hand, the temperature dependence of both PL intensity and decay lifetime can be well described by a complex model that introduces the contribution of vibrational emission into the traditional thermal quenching model. The present systematic study not only provides comprehensive guidance for evaluating the practical application potential of CAZO:Mn⁴⁺ and its analogues as light-conversion materials, but also provides detailed insights into the fundamental luminescence characteristics of the Mn⁴⁺ activator.