Luminescence And Photoelectric Coupling Performance Of Rare Earth Ions Doped Ferroelectric Glass-ceramic

Enhancement and modulation of luminescence is one of the very important topics in the application of rare earth doped luminescent materials.The traditional method is to incorporate rare earth ions in different matrix materials.The experimenters studied the luminescence response and its mechanism in different host or ligand environments.Among them,the crystal symmetry of the main crystal is one of the important factors affecting the optical properties of the luminescent material.Based on the sensitivity of rare earth ions’luminescence intensity to the symmetry of the crystal structure,the physical and chemical methods can reduce the symmetry of the crystal field around the luminescent center,and can also be used to change the optical properties of luminescent materials.Many strategies that can change the symmetry of the crystal field can modify the luminous intensity of rare earth-doped luminescent materials,such as pressure,temperature,and composition modification.Pressure can induce distortion of the crystal field around rare earth ions in inorganic materials.However,GPa-level pressure is required,which is not easy to achieve under ordinary experimental conditions.the chemical methods are essentially irreversible,such as modifying components and adding dopant ions,but they are prone to introduce defects and chemical heterogeneity.So,looking for unique luminescent materials,this system can couple the crystal structure symmetry with external physical stimuli,such as electric and magnetic fields.The properties of optical materials doped with rare earth ions can be reversibly and dynamically modified by external stimuli.According to the above-mentioned principle,ferroelectric glass-ceramics have the property of electro-induced structural change,and domain inversion will cause the change of crystal structure symmetry,means that the electric field can induce changes in the crystal field symmetry around the active doped ion.Therefore,this dissertation mainly discusses the electric field induced large and reversible modulation of luminescence,which improve the optical properties of rare earth doped luminescent materials,and provide theoretical and experimental basis for high-performance optical materials.This dissertation consists six chapters,the main contents are summarized as follows:Chapter one mainly reviews the rare earth ions doped luminescent materials,including the spectral properties of rare earth ions,downconversion luminescence,upconversion luminescence and energy transfer modes between rare earth ions.For host materials,the first chapter introduces the properties of ferroelectric materials,classification and preparation of ferroelectric glass-ceramics.Foremore,we summarize the research progress of electric field modified luminescence.And based on the influence of the surrounding environment on the luminescence of rare earth ions,we review the research status of the development of multifunctional sensing materials.Chapter two summarizes the technical route,raw materials and instruments of the test.This chapter introduces the specific test methods and principles of the samples in detail,such as the morphology,physics,thermology,ferroelectricity,structure and spectral properties,as well as the theoretical calculation of structural parameters and energy transfer.Chapter three designs and develops a Nd³⁺doped ferroelectric glass-ceramic material with near-infrared luminescence,and we studied its optical and optoelectronic coupling characteristics.At room temperature,the luminescence intensity of Nd³⁺ions can be reversibly modified by an electric field,and its near-infrared luminescence is enhanced by 4.6 times.Furthermore,the mechanism of enhancement and reversible modification is explored from the perspective of structural changes.The（012）crystal plane diffraction peak of the sample shifted to a large angle after loading the electric field,indicating that lattice shrinkage occurred.The absorption peak of the absorption spectrum of the sample was enhanced after polarization,which verified that the absorption rate was higher under the 808 nm pump light source.The XRD,absorption spectrum and emission spectrum all prove the coupling between the electric field and the enhancement factor.This chapter demonstrates the potential value of rare earth ions doped ferroelectric glass-ceramics in the application of optoelectronic materials.Chapter four mainly studies the upconversion and downconversion near-infrared emission of Yb³⁺/Tm³⁺codoped Li Nb O₃ ferroelectric glass-ceramics.The electro-induced structural changes of the ferroelectric lattice are employed,which makes the strong coupling relationship between the electric field and the photonics properties of rare earth ions.The emission intensity of the Tm³⁺:³H₄-⁴H₆ and ³F₄-⁴H₆ transitions was exceptionally enhanced by 2.6 and 3.2 times via ferroelectric polarization,respectively.The change of XRD lattice parameters showed that Yb³⁺/Tm³⁺ions were incorporated into Li Nb O₃ crystals,and the sample obtained both downconversion and upconversion near-infrared luminescence under the excitation of 980 nm laser.The XRD and Raman spectrum of the sample were changed simultaneously after loading the electric field,which indicated that a nanoscale structural change occurred within the sample.In order to understand the effect of symmetry on photoluminescence,the Judd-Ofelt theory was used to further analyze the potential physical process of luminescence modified luminescence,it shows that the weaken of crystal field symmetry will increase the probability of rare earth ions’radiation transition.Meanwhile,the luminescence response presents excellent reversibility and nonvolatility.This study provides a unique proposal for designing highly integrated stimuli responsive photonic materials toward a variety of applications.Chapter five mainly designs multifunctional materials for the thermal and electric fields sensing.Thermal and electric field have a significant impact on the luminescence of rare earth ions doped ferroelectric glass-ceramics.The influence of the external environment on the luminescence of rare earth ions can be used to develop multifunctional sensing materials.The Yb³⁺/Er³⁺codoped Bi₄Ti₃O₁₂ nanocrystalline composite has been developed for sensing material.The introduction of Bi₄Ti₃O₁₂nanocrystals into the glass matrix exceptionally enhances the upconversion emission of Er³⁺ions.The Yb³⁺/Er³⁺codoped Bi₄Ti₃O₁₂ nanocrystalline composite enables online temperature measurement under low power excitation density（0.75 W/cm²）,which can reduce the thermal effect of the laser.Yb³⁺/Er³⁺codoped nanocrystalline composite has excellent precision of temperature sensing in the temperature range of293-573 K.The value of absolute sensitivity S_a is 5.2×10^-3 K^-1.The maximum value of the relative error between the measured temperature and the actual temperature does not exceed 0.4%in the reliability test.For electric field sensing,the luminescence modulation of rare earth ions has been demonstrated in Yb³⁺/Er³⁺codoped ferroelectrics glass-ceramics through an electric field.The changes in the luminescence of Yb³⁺/Er³⁺codoped Bi₄Ti₃O₁₂ glass-ceramics are used to reflect the changes in the electric field.The inclusion of nanocrystals in the glass matrix greatly enhances the electrical resistance.The upconversion green-light emissions of rare earth ions are effectively enhanced more than twice via polarization engineering.This chapter demonstrates that rare earth ions codoped ferroelectric glass-ceramics is a promising multifunctional sensing material.Chapter six is the concluding part of this dissertation,which summarizes the research results,and points out the shortcomings of experimental design and give some suggestions for future work.