Investigation Of Rare Earth And Transition Metal Ions Codoped Dual-phase Functional Glass Ceramics

Oxyfluoride glass ceramics combine the advantages of low phonon energy environment of fluoride nanocrystal and high stability of oxide glass,so they are suitable as matrix materials of luminescent ions.However,there may exist energy transfer?ET?process between different ions,which may lead to fluorescence-quenching phenomenon when more than two kinds of luminescent ions are codoped into the conventional single-phase oxyfluoride glass ceramics.Therefore,this paper aims to develop a novel dual-phase oxyfluoride glass ceramics to solve this problem.By adjusting the composition of glass formula and optimizing the heat-treatment condition,we have exploited dual-phase oxyfluoride glass ceramics comprising NaYF₄ and NaAlSiO₄ nanocrystals.And three doping strategies of Yb³⁺/Er³⁺/Cr³⁺,Yb³⁺/Nd³⁺/Cr³⁺,Tm³⁺/Cr³⁺were adopted to explore the application of this novel dual-phase glass ceramics in the field of optical temperature sensing and ecological agriculture.The research content and results are as follows:?1?Yb³⁺/Er³⁺/Cr³⁺codoped dual-phase oxyfluoride glass ceramics were successfully fabricated through a melt-quenching method and subsequent heat-treatment.First,XRD and TEM show that the glass after heat-treatment at 670? for 2 h precipitated cubic phase NaYF₄ and orthorhombic phase NaAlSiO₄ nanocrystals,respectively.With the enhancement of heat treatment temperature,the grain size of NaYF₄ and NaAlSiO₄ increased.Then the photoluminescence?PL?spectra and lifetime decay curves of dual-phase glass ceramics and precursor glasses were tested,which suggested that Yb³⁺/Er³⁺entered into the NaYF₄nanocrystals to replace Y³⁺and Cr³⁺entered into NaAlSiO₄ nanocrystals to replace Al³⁺in Yb³⁺/Er³⁺/Cr³⁺codoped dual-phase glass ceramics.In order to further prove that Er³⁺and Cr³⁺entered into different nanocrystals respectively,we measured PL spectra of precursor glass and glass ceramics with various doping concentrations of Cr³⁺,which reveals ET from Er³⁺to Cr³⁺in precursor glass,while ET between Er³⁺and Cr³⁺in dual-phase glass ceramics is effectively inhibited due to spatial isolation.Finally,we analyzed the relationship between the optical properties of Er³⁺(Cr³⁺)and temperature.The results show that the fluorescence intensity ratio?FIR?between ²H_11/2?⁴I_15/25/2 and ⁴S_3/2?⁴I_15/25/2 transitions from Er³⁺monotonously increases with the increase of temperature and its sensitivity is better than many other Yb³⁺/Er³⁺codoped materials.FIR of Cr³⁺(I₇₀₄)to Er³⁺(I₆₆₈)increases monotonously with the increase of temperature and its relative sensitivity?S_R?reaches the maximum value of 1.64% K^-1 at 447 K.The fluorescence lifetime of Cr³⁺monotonously decreases with the increase of temperature and S_R reaches the maximum value of 0.58%K^-1 at 392 K.Therefore,Yb³⁺/Er³⁺/Cr³⁺codoped dual-phase glass ceramics have three modes to measure temperature based on FIR between²H_11/2?⁴I_15/25/2 and⁴S_3/2?⁴I_15/25/2 transitions from Er³⁺,FIR from Cr-Er non-thermally coupled system and fluorescence lifetime of Cr³⁺,which open up a new research direction in optical temperature sensing field.?2?Similarly,Yb³⁺/Nd³⁺/Cr³⁺codoped dual-phase glass ceramics were successfully synthesized by melting-quenching and heat-treatment.According to PL spectra and lifetime decay curves of precursor glass and glass ceramics,Yb³⁺/Nd³⁺entered into NaYF₄nanocrystals to replace Y³⁺and Cr³⁺entered into NaAlSiO₄ nanocrystals to replace Al³⁺.Subsequently,the relationship between the optical properties of Nd³⁺(Cr³⁺)and temperature was studied.The results show that Yb³⁺/Nd³⁺/Cr³⁺codoped dual-phase glass ceramics have three modes to measure temperature based on FIR between ⁴F_7/2/⁴S_3/2?⁴I_9/2/2 and ⁴F_3/2?⁴I_9/2transitions from Nd³⁺,FIR from Cr-Nd non-thermally coupled system and the fluorescence lifetime of Cr³⁺.FIR between ⁴F_7/2/⁴S_3/2?⁴I_9/2/2 and ⁴F_3/2?⁴I_9/2/2 transitions from Nd³⁺increases monotonously with the increase of temperature and S_R reaches the maximum value of1.05%K^-1 at 416 K so that its accuracy is better than that of many other rare earth doped materials.FIR of Cr³⁺(I₇₀₄)to Nd³⁺(I₇₅₀)decreases monotonously with the increase of temperature and S_R reaches the maximum value of 2.25%K^-1 at 385 K.The fluorescence lifetime of Cr³⁺decreases monotonously and S_R reaches the maximum value of 0.59%K^-1at389 K.According to temperature sensitivity,the temperature measurement performance of Yb³⁺/Nd³⁺/Cr³⁺codoped dual-phase glass ceramics is better than that of Yb³⁺/Er³⁺/Cr³⁺codoped dual-phase glass ceramics.In addition,high-sensitivity temperature ranges of these three modes are different.FIR from Cr-Nd non-thermally coupled system and the fluorescence lifetime of Cr³⁺are more suitable for the temperature range from room temperature to 400 K,while FIR between⁴F_7/2/⁴S_3/2?⁴I_9/2/2 and⁴F_3/2?⁴I_9/2/2 transitions from Nd³⁺is more suitable for the temperature range from 400 to 573 K.This multi-mode temperature sensor can combine the high-sensitivity temperature range of different sensing modes and generate the larger temperature range with high accuracy.Therefore,Yb³⁺/Nd³⁺/Cr³⁺codoped dual-phase glass ceramics have a great application prospect in the field of optical temperature sensing.?3?Tm³⁺/Cr³⁺codoped dual-phase glass ceramics were prepared and its application potential in ecological agriculture field was researched.By analyzing the relationship between PL spectra and the doping concentrations of TmF₃ and Cr₂O₃,it was found that the optimal doping concentrations of TmF₃ and Cr₂O₃ are 1.0 mol% and 0.1 mol%respectively.Similarly,Tm³⁺entered into NaYF₄ nanocrystals to replace Y³⁺ and Cr³⁺entered into NaAlSiO₄nanocrystals to replace Al³⁺.So that ET between Tm³⁺and Cr³⁺in dual-phase glass ceramics is effectively suppressed due to spatial isolation.Photoluminescence excitation?PLE?and PL spectra show that Tm³⁺/Cr³⁺codoped dual-phase glass ceramic converts ultraviolet and green light into blue and red light,so it is a dual-energy light conversion material.Since chlorophyll-?and chlorophyll-? mainly absorb blue and red light,this dual-energy light conversion glass ceramic,which is able to effectively promote the photosynthesis of green plants and improve the yield of crops,can be used as the building material for greenhouses.