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

A novel upconversion phosphor, Ca 3 (VO 4 ) 2 co-doped with Yb 3+ and Er 3+ , 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 Yb 3+ and 0.005 for Er 3+ , enabling maximum luminescent efficiency. Spectroscopic investigations including upconversion photoluminescence, excitation, and emission spectra confirmed that the upconversion follows a distinct energy transfer mechanism: Yb 3+ ( 2 F 5/2 ) + Er 3+ ( 4 I 11/2 ) → Yb 3+ ( 2 F 7/2 ) + Er 3+ ( 4 F 7/2 ). In addition to its excellent luminescent properties, the Ca 3 (VO 4 ) 2 : 0.03Yb 3+ /0.005Er 3+ 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 Ca 3 (VO 4 ) 2 : 0.03Yb 3+ /0.005Er 3+ a promising candidate for display and lighting technologies.