Optical Thermometry Based on Vibration Sidebands in Y₂MgTiO₆:Mn⁴⁺ Double Perovskite

Mn⁴⁺-doped Y₂MgTiO₆ phosphors are synthesized by the traditional solid-state method. Powder X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectrometer are employed to characterize the samples. The Mn⁴⁺-doped Y₂MgTiO₆ phosphors show the far-red emission at ∼715 nm, which is assigned to the ²E_g → ⁴A₂ spin-forbidden transition of Mn⁴⁺. The temperature-dependent luminescent dynamics of Mn⁴⁺ is described by a complete model associated with electron-lattice interaction and spin-orbit coupling. The noncontact optical thermometry of Y₂MgTiO₆:Mn⁴⁺ is discussed based on the fluorescence intensity ratio of thermally coupled anti-Stokes and Stokes sidebands of the efficient ∼715 nm far-red emission in the temperature range of 10-513 K. The maximum sensor sensitivity of Y₂MgTiO₆:Mn⁴⁺ is determined to be as high as 0.001 42 K^-1 at 153 K, which demonstrates potential applications for the optical thermometry at low-temperature environments.