Color tunable Bi3+/Eu3+ co-doped La2ZnTiO6 double perovskite phosphor for dual-mode ratiometric optical thermometry

Rigorous temperature measurement employed to characterize physic-chemical state has compelled scientists to explore more novel materials for contactless optical thermometry, which must overcome the drawbacks of low sensitivity and poor signal discriminability. Here, a novel dual-mode optical thermometer La2ZnTiO6: Bi3+/Eu3+ is designed, prepared and characterized via XRD, XPS, EPR, SEM, EDS, PL spectra and decay time. Under 350 nm excitation, the energy transfer process from Bi3+ to Eu3+ allows the samples to demonstrate adjustable multi-color emissions. The temperature-dependent emission spectra display that the luminescence intensity of Bi3+ ions decreases quite faster than that of Eu3+ ions with temperature, leading to a significant chromaticity shift (∆E = 224 ×10−3 in 293–473 K) visible to naked eyes. Based on fluorescence intensity ratio of Eu3+ versus Bi3+ (FIR = IEu/IBi), the sample shows the maximum relative sensitivity (Sr) of ~1.50% K−1 at 293 K and excellent signal discriminability. Meanwhile, the 5D0→7F2 transition of Eu3+ ions shows a thermal-responsive lifetime with the optimal Sr of 1.23% K−1 at 573 K. This work suggests that the La2ZnTiO6: Bi3+/Eu3+ double perovskite phosphor has a great potential for dual-mode optical thermometry, being beneficial to obtain precise, sensitive and reliable temperature detection.