Luminescence Properties Of ?-SrGaBO₄:xMn²⁺ And CeO₂:0.05Eu³⁺,M²⁺?M=Ca,Sr,Ba?

Luminescent materials are the most widely usedfunctional materials in our life.How to improve the properties of luminescent materials has always been a hot topic for researchers in many countries.Host and activator are the main components of inorganic solid luminescent materials,and the host is the most important part of them.As the host of luminescent materials,some compoundscan not only have energy transfer with activators to enhance the luminescent intensity of activator ions or groups,but also have appropriate band gaps or defectsto bring about self-luminescence phenomenon.In recent years,researches on self-luminescence materials have attracted increasing attention.Compared with the host,the doping amount of activator is small,but it is the main component of the luminescent center,which plays a decisive role in the luminescent properties.So the key to improvingthe luminescent performanceis to increase the luminous efficiency ofactivator ions or groups.The concrete research content is as follows:1.A host material?-SrGaBO₄ was synthesized by high temperature solid-state reaction.PL results showed that under 408 nm excitation?-SrGaBO₄ presents self-luminescence at 540 nm.Further studies showed that there are oxygen defects and two different trap depths in?-SrGaBO₄ host.So the cause of self-luminescence of?-SrGaBO₄ host is electron-hole recombination,that is,the oxygen defects can absorb the holes from the valence band to form the lower energy level.Then the holes in the low energy levels will recombine with electrons,releasing energy to emit light.2.?-SrGaBO₄:xMn²⁺?x=0,0.001,0.002,0.003,0.004,0.005,0.006?samples were successfully synthesized by high temperature solid-state reaction.XRD results showed that the as-synthesized samples belong toorthorhombic system.PL results indicated that the best Mn²⁺doping amountis 0.003.This is because Mn²⁺ions are in the tetrahedral crystal field,its have an overlapping emission range with?-SrGaBO₄.So optimum Mn²⁺content level can greatly enhance luminescent intensity.If Mn²⁺ions doping concentration x>0.003,the luminescent intensity of?-SrGaBO₄:xMn²⁺will significantly decrease due to energy transfer between the nearest Mn²⁺ions.According to the diffuse reflectance spectrum analysis,we can know that the[⁴A₁?⁴G?+⁴E?⁴G?]energy level of Mn²⁺is inside the conduction band,indicating that energy transfer will occur between the host?-SrGaBO₄ and Mn²⁺through conduction bands.?-SrGaBO₄was successfully synthesized by high temperature solid-state reaction and microwave-assisted solid-state reaction.This study showed microwave-assisted solid-state synthesis can decrease reaction temperature and shorten the synthesis time.XRD results showed that both methods can synthesize pure phase?-SrGaBO₄,which belongs to orthorhombic system.Through SEM tests we can see that the particle size of?-SrGaBO₄ is smallerand the aggregation of samples synthesized bymicrowave-assisted solid-state reaction is significantly reduced.PL results and fluorescence lifetime tests showed that?-SrGaBO₄ prepared by microwave-assisted solid-state method has stronger luminescence intensity and longer fluorescence lifetime.3.CeO₂:0.05Eu³⁺,0.05M²⁺?M=Ca,Sr,Ba?samples were synthesized by high temperature solid-state reaction.XRD results showed that the as-synthesized samples belong to cubic system.SEM images indicated that the synthesized particles are nearly spherical,and the doped of Ca²⁺,Sr²⁺,and Ba²⁺ions all increased the grain size of the sample.When the doped ion was Ca²⁺,the grain size was the largest.PL results showed that under 375 nm and 467 nm excitation,the CeO₂:0.05Eu³⁺,0.05M²⁺?M=Ca,Sr,Ba?can obtain ⁵D₀?⁷F₁?592 nm?and ⁵D₀?⁷F₂?611 nm?characteristic transition emission belong to Eu³⁺.It was found that the co-doped samples have stronger luminescence intensity and longer fluorescence lifetime than the undoped samples,and the luminescence intensity was the strongest when the co-doped ion was Ca²⁺.4.CeO₂:0.05Eu³⁺,x Ca²⁺?x=0,0.05,0.10,0.15,0.20,0.25?samples were synthesized by high temperature solid-state reaction.The relation between Ca²⁺ions doping concentration and luminescent intensity was further investigated.When x=0.10,the characteristic transitionemission intensity of Eu³⁺⁵D₀?⁷F₁?592 nm?and⁵D₀?⁷F₂?611 nm?reached the highest,and the fluorescence lifetime was the longest.Moreover,the emission color of CeO₂:0.05Eu³⁺,xCa²⁺is related to the amount of Ca²⁺ions.When x?0.10,as Ca²⁺ions doping concentration increases,the luminescence color of the samples was getting closer to the orange-red region;when x>0.10,the luminescence color began to tend to the orange-yellow region.