Study On Valence Regulation And Optical Application Of Manganese Doped Gallium Garnets

Transition metal manganese ion-doped luminescent materials have gradually penetrated various fields in daily production and life,and the optical properties of the doped luminescent materials are affected by the local coordination environment of manganese ions.When doped into the lattice of garnets,manganese ions will exhibit a variety of valences,including+2,+3,and+4.At present,most studies have reached a consensus on the emission characteristics of Mn4+ions in the garnets structure,and the related energy level transition lines can be identified.However,in related research reports,the attribution of the corresponding optical transition is still unclear in the optical analysis related to the Mn²⁺and Mn³⁺ion-doped garnets.This may be because the two manganese ions showing broad emission lines and overlapping peak positions of related emission spectra which will be increasing the difficulty of distinguishing ion spectra.Therefore,based on the above-mentioned problems,this work firstly determined the valence composition of manganese ions and the assignment of the emission peaks in the spectrum of the manganese-doped Y3Ga5O12（YGG）,and then further realized adjusting of manganese ions valence state by ion doping.The application potential of manganese ion-doped gallium garnet materials in temperature sensing has been studied and developed.The main experimental conclusions are as follows:（1）Mn:YGG powder was prepared by the high-temperature solid-phase method,the sintering atmosphere was air,and then annealed in the reducing atmosphere.As the excitation wavelength is 355 nm,the main peak of the Mn:YGG emission spectrum is located near 674nm wavelength,which comes from the transition of Mn⁴⁺.When the excitation wavelength is275 nm,the main peak of the emission spectrum wavelength is located near 613 nm,this ion transition spectrum here is still controversial.This work firstly used temperature-dependent photoluminescence spectroscopy,X-ray photon energy spectroscopy,electronic paramagnetic resonance spectroscopy test methods to characterize the characteristics of the ions,and determined that the emission peak at the 613 nm wavelength comes from Mn³⁺instead of Mn²⁺.Then,through the introduction of Zr⁴⁺to adjusted the valence state of manganese ions from+4to+2,so that manganese ions with+2,+3,and+4 valences can coexist in YGG.（2）The optical temperature sensing properties of manganese doped YGG and Lu GG were further studied.In the YGG1-y-Lu GGy system,when the smaller radius Lu³⁺are introduced,the emission spectra of Mn³⁺and Mn⁴⁺are both blue-shifted,and the resistance of Mn³⁺to thermally induced fluorescence quenching can be improved.Combining the ion transition characteristics of Mn³⁺and Mn⁴⁺,the samples of Mn:YGG1-y-Lu GGy exhibits excellent temperature sensing performance,which further proves that manganese ion-doped gallium garnet has great application potential in the field of temperature sensing.（3）High sensitivity is an important development direction of luminescence thermometers.For temperature sensing applications of manganese ions,a multi-ion co-doping method is used to improve its temperature sensing performance,the Nd³⁺and Mn⁴⁺ions are co-doped into YGG.The temperature-related spectroscopic investigations show that the ²Eg→⁴A2g transition of Mn⁴⁺ion and the ⁴F_5/2→⁴I_9/2 emission of Nd³⁺ion show strong fluorescence quenching and fluorescence enhancement respectively when the temperature is higher than 240 K.The obvious difference in fluorescence spectra between the two ions show excellent temperature-sensing performance.The obtained relative sensitivity showed a maximum value of 7.90%·K^-1 at 280K,and remained above 5.00%·K^-1 in the whole physiological temperature range（from 298 K to 323 K）.By rationally designing research ideas and experimental programs,the research results of this subject have very important guiding significance in the basic research related to the manganese-doped garnet materials and improving its performance in temperature sensing.