Study On Mechanoluminescence And Its Enhancement Mechanism Of Bielemental Niobate Materials

Mechanoluminescence refers to the luminescence caused by some materials under mechanical force.Due to its characteristics of accurately presenting pressure distribution,luminescence intensity proportional to stress,presenting pressure value and low pressure threshold,Mechanoluminescence phosphors are favored by researchers and have made significant progress in artificial intelligence,Internet of things,biotechnology and other fields.Exploring new Mechanoluminescence materials,improving luminescence intensity,uncovering their internal luminous principles,and expanding their applicability to a wider range of scenarios remain significant challenges.Niobate materials are important members of the Mechanoluminescence materials family,which include Li Nb O₃,Na Nb O₃,and other products that have been developed through the addition of new elements to regulate their structure.In this study,we prepared a series of niobate materials basis on group-II elements and investigated their Mechanoluminescence properties.We then added Na⁺to these group-II elements niobate materials to further study their properties.Additionally,we described the defect properties and heterojunction properties of niobate materials using first principles calculations.The main focus of this paper is on these research endeavors.（1）MNb O₃:Pr（M=Mg,Ca,Sr,Ba）materials were synthesized and characterized for their crystal structures.A Mechanoluminescence composite elastomer was prepared by embedding the materials into an epoxy resin and their Mechanoluminescence properties were studied using a self-assembled experimental platform.It was found that only Sr₂Nb₂O₇:Pr exhibited Mechanoluminescence phenomena under the synthesis conditions described in the paper.Differences in defect properties between the samples were investigated using thermoluminescence and diffuse reflectance spectroscopy.Ca₂Nb₂O₇ and Sr₂Nb₂O₇ defect properties were calculated using first-principles calculations,providing a theoretical basis for understanding the differences in Mechanoluminescence performance between the different group-II elements in niobate materials.（2）By introducing Na⁺ions,the Mechanoluminescence properties of group-II elements in niobate materials were enhanced.Results showed that the Mechanoluminescence intensity of MgNb O₃:Pr and Ba Nb O₃:Pr increased after introducing Na⁺ions.Heterojunction models were established based on structural characterization.In addition,the electronic and defect properties of MgNb O₃:Pr doped with Na⁺ions were studied using diffuse reflectance spectroscopy,thermoluminescence,and positron annihilation spectroscopy,indicating the importance of heterojunction formation and defects in enhancing Mechanoluminescence intensity.Furthermore,the reason for the enhanced Mechanoluminescence intensity after introducing Na⁺ions in Sr₂Nb₂O₇:Pr was analyzed,providing guidance for the design of Mechanoluminescence materials.（3）First-principles calculations were used to analyze the defect properties of MgNb₂O₆/Na Nb O₃ crystals.The relationship between defects and Mechanoluminescence was established by calculating the density of states and formation energies of different defect types.Here,defect levels generated within the bandgap was observed.The heterojunction model of MgNb₂O₆/Na Nb O₃ was established,and its band edges,charge distribution,and density of states were calculated,revealing that enhanced Mechanoluminescence intensity was due to the high concentration of certain types of traps at appropriate positions within the bandgap.