An efficient energy transfer process in Nd3+:Yb3+ co-doped SrF2 powders containing Al3+ and prepared by the combustion synthesis technique

Abstract

Strontium fluoride (SrF₂) powders containing aluminum (Al³⁺) and doped with rare-earth neodymium (Nd³⁺) and ytterbium (Yb³⁺) were synthesized using the combustion synthesis technique. Heat-treated (700 °C for 3 h) powder samples presented the SrF₂ network arranged in a face-centered cubic phase. Under pulsed laser excitation at λ = 750 nm, at room temperature, near-infrared luminescence attributed to 4f–4f electronic relaxation ⁴F_3/2 → ⁴I_9/2 from Nd³⁺ was observed in the spectral range λ ∼ 850–930 nm for both Nd³⁺ doped and Nd³⁺:Yb³⁺ co-doped SrF₂ powder samples. Nd³⁺:Yb³⁺ co-doped SrF₂ powder samples presented an additional luminescence band peak at λ ∼ 980 nm assigned to the ²F_5/2 → ²F_7/2 transition of Yb³⁺. Quenching of the luminescence originating from the ⁴F_3/2 state of Nd³⁺ was observed in co-doped samples and the phenomenon was assigned to energy transfer (ET). ET was investigated by analysing the near-infrared luminescence dynamics of Nd³⁺ using the Inokuti–Hirayama model. The energy transfer mechanism was found to be of a quadrupole–quadrupole type with efficiency as high as 62%. Our results show that this system is a potential phosphor for photonics applications involving near-infrared light sources.