Regulating the redshift of the charge transfer band edge and antithermal quenching by ion substitution strategy in YP1-xVxO4:Eu3+ phosphor

Abstract

The redshift of the charge transfer band (CTB) edge of phosphor induced by temperature rise is pervasively accompanied by antithermal quenching. Accordingly, exploring the mechanism of the CTB redshift is thus not only propitious for optimizing the sensitivity of optical thermometry but also tenders a new idea for the design of antithermal quenching phosphors. Herein, a family of YP1-xVxO4:Eu3+ phosphors were designed via the V5+/P5+ ion substitution strategy. With the increase of the V5+ ratio, the relative integral intensity of the 5D0→7F2 transition multiplies from 1.25 to 28.67 times under CTB edge excitation. Moreover, by Gaussian fitting, the reduction degree of vanadate band gap energy 1E (1T1)→1B2 (1T2), 1A2 (1T1)→1B2 (1T2) increased from 0.122 eV and 0.065 eV to0.162 eV and 0.083 eV, respectively, in the range of 303–523 K. Both reveal an enhance in redshift of the excitation spectra. The decrease of charge transfer state (CTS) energy level and the alteration of photoelectron thermal population are two mechanisms that induce CTB redshift. Specifically, the decrease of the CTS level is dominant in the YPO4:Eu3+ sample, and the thermal population of the higher vibrational levels of the VO43−ground state is dominant in the presence of a tiny amount of V5+ doping. In addition, according to the experimental phenomenon, a dual-mode temperature sensing scheme based on excitation intensity ratio (EIR) and single band ratiometric (SBR) is proposed. Y0.9P0.1V0.9O4:0.1Eu3+ achieves a maximum sensitivity of Sr-max = 4.040 % K−1 and a minimum temperature determination uncertainty of δT = 0.124 K at 323 K, which excellent performance indicates that this is a promising non-contact optical thermometer.