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In the dual‐emitting Eu3+‐activated Sr2NaMg2V3O12 garnet, vibrationally induced thermometric response and thermochromic luminescence are investigated for the first time. Based on the diverse thermal quenching of VO43− and Eu3+ along with the advantage of variation in the fluorescence intensity ratio, a potential phosphor for sensitive dual‐mode ratiometric and colorimetric temperature sensors is proposed in which maximum absolute and relative sensitivity of 0.0135 K−1 and 1.61% K−1 are obtained at 420 K with a temperature resolution <0.2 K. Efficient thermochromic luminescence in which colorific shift from white (300 K) to red (500 K) is observed such that the requirement of larger number of phonons weakens the nonradiative relaxation of Eu3+, resulting in slow quenching, substantiated by estimating radiative and nonradiative decay rates by the 4f–4f intensity method. In contrast, a strong vibrational coupling of excited electrons of the VO43− complex is identified and verified by means of temperature‐dependent Raman and photoluminescence excitation spectra for the first time. Consequently, an increased thermal population of vibrational levels favors rapid thermal quenching of luminescence of VO43− via crossover mechanism. Hence dual‐centered Sr2NaMg2V3O12:Eu is an efficient thermometric and thermochromic luminescent material for optical thermometry and safety sign applications in a high‐temperature environment.

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Monoclinic (P21/n) structure of B-site ordered double perovskites Ba2R2/3TeO6 (R = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) is elucidated from XRD, Raman and IR spectroscopy. The maximum relative temperature sensitivity of Ba2Y2/3TeO6:Eu3+ between 300–500 K is 0.18% K−1.