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

Herein, YNbO4 (YNO):Bi3+,Ln3+ (Ln = Dy, Eu) phosphors were manufactured though high-temperature solid-phase reaction. Their structural properties, optical characteristics and energy transfer mechanisms (Bi3+-> Ln3+) were analyzed in detail, and their potential application in optical thermometry was explored. Under 312 nm excitation, YNO:Bi3+,Ln3+ phosphors show broad emission from Bi3+ ions (3P1 -> 1S0) and sharp peaks from 4f-4f transitions of Ln3+ ions. YNO:Bi3+,Ln3+ samples exhibit high sensitivity and superior thermochromic properties in temperature sensing. For YNO:Bi3+,Dy3+ phosphor, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) reach 14.25 %K-1 (573 K) and 1.48 %K-1 (444 K), respectively. For YNO:Bi3+,Eu3+ phosphor, the maximum Sa and Sr reach 38.21 %K-1 (573 K) and 1.58 %K-1 (445 K), respectively. And the chromaticity shift of emission from YNO:Bi3+,Eu3+ phosphor is 0.38 for temperature from 303 to 573 K. Such results suggest that YNO:Bi3+,Ln3+ phosphors can be candidate for visual and highly sensitive optical thermometry.