Optical thermometry based on Bi3+,Ln3+ co-doped YNbO4 (Ln = Dy, Eu) phosphors

Herein, YNbO 4 (YNO):Bi 3+ ,Ln 3+ (Ln = Dy, Eu) phosphors were manufactured though high-temperature solid-phase reaction. Their structural properties, optical characteristics and energy transfer mechanisms (Bi 3+ →Ln 3+ ) were analyzed in detail, and their potential application in optical thermometry was explored. Under 312 nm excitation, YNO:Bi 3+ ,Ln 3+ phosphors show broad emission from Bi 3+ ions ( 3 P 1 → 1 S 0 ) and sharp peaks from 4f-4f transitions of Ln 3+ ions. YNO:Bi 3+ ,Ln 3+ samples exhibit high sensitivity and superior thermochromic properties in temperature sensing. For YNO:Bi 3+ ,Dy 3+ phosphor, the maximum absolute sensitivity ( S a ) and relative sensitivity ( S r ) reach 14.25 %K −1 (573 K) and 1.48 %K −1 (444 K), respectively. For YNO:Bi 3+ ,Eu 3+ phosphor, the maximum S a and S r reach 38.21 %K −1 (573 K) and 1.58 %K −1 (445 K), respectively. And the chromaticity shift of emission from YNO:Bi 3+ ,Eu 3+ phosphor is 0.38 for temperature from 303 to 573 K. Such results suggest that YNO:Bi 3+ ,Ln 3+ phosphors can be candidate for visual and highly sensitive optical thermometry.