Structural Characteristics,Luminescence Properties And Mechanism Of Ca₃Ga₄O₉ Optical Information Storage Materials

The charge carrier trapping material with multiple layers of deep traps provides promising application for erasable optical data storage,i.e.,information such as letters and patterns can be recorded in different depths of the media through UV/blue light and then read out by different energy of light or thermal stimulation.Optical data storage in this way has many obvious advantages,such as large capacity,fast speed et al.Therefore,it is very necessary to develop optical information storage materials with excellent performance.In this paper,a series of Ca₃Ga₄O₉:Bi³⁺samples with different Bi³⁺doping concentrations were prepared by high-temperature solid-phase method,Then,with the optimized Bi doping concentration(0.03mol),a series of Ca₃Ga₄O₉:Bi³⁺,Zn²⁺samples were synthesized by co-doping with different concentrations of Zn²⁺.X-ray diffraction(XRD),photoluminescence and isometric thermoluminescence spectra were collected to characterize these samples.The conclusions were obtained as follows:(1)For a series of Ca₃Ga₄O₉:Bi³⁺samples,they have different PL emission because Bi³⁺ions are easily affected by the crystal field.In the Ca₃Ga₄O₉ crystal structure,there are two different Ca²⁺lattice sites,which provide different coordination environments for Bi³⁺,making the sample display the yellow and green emission of Bi³⁺under different excitation wavelengths;Moreover,by changing the Bi³⁺doping concentration,the distortion of the crystal lattice in the Ca₃Ga₄O₉ crystal structure is caused,so as to realize the regulation of the light-emitting color of the Ca₃Ga₄O₉:Bi³⁺material.Through the three-dimensional thermoluminescence test,it is observed that the trap distribution of Ca₃Ga₄O₉has been modified by the doping of Bi³⁺.With the increase of Bi³⁺concentration,the thermoluminescence peak moves to the shallow side.(2)For a series of Ca₃Ga₄O₉:Bi³⁺,Zn²⁺samples,Zn²⁺codoping enhances the emmission of Ca₃Ga₄O₉:Bi³⁺,making the sample display three different emission of Bi³⁺under different excitation wavelengths and the excitation spectra of broaden to longer wavelength region due to the charge compensation and lattice distortion.Through the three-dimensional thermoluminescence,it is noticed that the incorporation of Zn²⁺makes up for the cation vacancies,reduces the number of shallow traps and increases the number of deep traps,which is more conducive to the storage of optical information.In conclusion,the research results of this thesis show that replacing Ca²⁺and Ga³⁺in Ca₃Ga₄O₉ with an appropriate amount of Bi³⁺and Zn²⁺can change the luminescence and trap properties of the material,and effectively improve the optical information storage performance of the sample.