Luminescence of Mn⁴⁺ in a Zero-Dimensional Organic–Inorganic Hybrid Phosphor [N(CH₃)₄]₂ZrF₆ for Dual-Mode Temperature Sensing

Searching for new low-dimensional organic–inorganic hybrid phosphors is of great significance due to their unique optical properties and wide applications in the optoelectronic field. In this work, we report a Mn4+ doped zero-dimensional organic–inorganic hybrid phosphor [N(CH3)4]2ZrF6, which was synthesized by a wet chemical method. The crystal structure, thermal stability, and optical properties were systemically investigated by means of XRD, SEM, TG-DTA, FTIR, DRS, emission spectra, excitation spectra, as well as decay curves. Narrow red emission with high color purity can be observed from [N(CH3)4]2ZrF6:Mn4+ phosphor, which maintains effective emission intensity even at room temperature, indicating its potential practical application in WLEDs. In the temperature range of 13–295 K, anti-Stokes and Stokes sidebands of Mn4+ ions exhibit different temperature responses. By applying the emission intensity ratio of anti-Stokes vs. Stokes sidebands as temperature readout, an optical thermometer with a maximum absolute sensitivity of 2.13% K−1 and relative sensitivity of 2.47% K−1 can be obtained. Meanwhile, the lifetime Mn4+ ions can also be used for temperature sensing with a maximum relative sensitivity of 0.41% K−1, demonstrating its potential application in optical thermometry.