Strong green upconversion luminescence of rare earth Yb3+/Er3+ co-doped Ca3(VO4)2 phosphor for optical sensing

Abstract

A novel upconversion phosphor, Ca₃(VO₄)₂ co-doped with Yb³⁺ and Er³⁺, was successfully synthesized via a high-temperature solid-state method. Under 980 nm near-infrared excitation, this material exhibits remarkable upconversion luminescence, with intense green emissions at 527 nm and 550 nm, and a weaker red emission at 657 nm. The optimal doping concentrations were determined to be 0.03 for Yb³⁺ and 0.005 for Er³⁺, enabling maximum luminescent efficiency. Spectroscopic investigations including upconversion photoluminescence, excitation, and emission spectra confirmed that the upconversion follows a distinct energy transfer mechanism: Yb³⁺ (²F_5/2) + Er³⁺ (⁴I_11/2) → Yb³⁺ (²F_7/2) + Er³⁺ (⁴F_7/2). In addition to its excellent luminescent properties, the Ca₃(VO₄)₂: 0.03Yb³⁺/0.005Er³⁺ phosphor exhibits reliable optical thermal sensitivity over a wide temperature range (298–673 K), with a peak relative sensitivity of 1.11 % K⁻¹ at 298 K. These outstanding optical characteristics make Ca₃(VO₄)₂: 0.03Yb³⁺/0.005Er³⁺ a promising candidate for display and lighting technologies.