Study On Preparation,Structure,Luminescence And Temperature Sensitive Properties Of Fluorapatite Transparent Glass-Ceramic Materials

Rare earth-doped fluorescent materials have broad prospects for special temperature measurement fields such as high-voltage power systems,oil wells,and biomedical testing,and have become a research hotspot in the world.Fluorapatite fluorescent transparent glass ceramics have the advantages of low phonon energy,high sensitivity,good thermal stability and easy preparation and processing,and have advantages in the above-mentioned application fields.Therefore,the development of fluorapatite fluorescent transparent glass ceramic materials has important theoretical significance and application prospects,which opens up new ways for the application of fluorescent materials and promotes the preparation and application of related optical temperature sensors.In this paper,rare earth doped CaF₂-ZnO-P₂O₅-B₂O₃,BaF₂-ZnO-P₂O₅-B₂O₃ phosphate and CaF₂-ZnO-P₂O₅-Ca O-Si O₂ silicate glasses were prepared by high temperature melting method.Fluoroapatite transparent glass ceramics were successfully prepared by controlled crystallization.The structure and thermal stability of the glass were analyzed by DSC,XRD,Raman spectrum and infrared spectrum.TEM characterization methods were used to analyze the structure and microscopic morphology of fluorapatite glass ceramics.The luminescent mechanism,optical properties and energy transfer process of rare earth doped glass and glass ceramics were studied by measuring the transmittance spectra,excitation spectra,emission spectra and fluorescence decay curves.The color coordinates and temperature of samples were calculated by CIE 1931 color coordinate software.Finally,the optical temperature sensitivity of the samples was studied by fluorescence intensity ratio technique.The main results are as follows.1.CaF₂-ZnO-P₂O₅-B₂O₃ system:the infrared and Raman spectra of Yb³⁺/Ho³⁺doped CaF₂-ZnO-P₂O₅-B₂O₃ system glass show that the glass sample has a disordered network structure,and the structural groups in the glass are[BO₄],[BO₃]and[PO₄].From the variable power emission spectra of Yb³⁺/Ho³⁺doped glass,it can be obtained that the number of laser photons n absorbed by Ho³⁺at 546 nm and 659 nm are 1.71 and 2.05,respectively,indicating that only two photons are involved in ⁵F₄/⁵S₂→⁵I₈ and ⁵F₅→⁵I₈ transition process.Under 980nm excitation,the absolute sensitivity of Yb³⁺/Ho³⁺doped glass is 0.05 K^-1 in the range of453-653 K,and the relative sensitivity reaches the maximum value of 9×10^-2%K^-1 at 653 K.In the Tb³⁺/Eu³⁺doped CaF₂-ZnO-P₂O₅-B₂O₃ system,the energy transfer of Tb³⁺/Eu³⁺in glass is analyzed in the form of Tb³⁺→Eu³⁺electric dipole interaction by fluorescence lifetime and Inokuuti Hirayama model theory.The absolute sensitivity of Tb³⁺/Eu³⁺doped CaF₂-ZnO-P₂O₅-B₂O₃ glass is 1.86%K^-1 at 403-753 K,and the relative sensitivity reaches the maximum of 1.24%K^-1 at 753 K.Tb³⁺/Eu³⁺doped CaF₂-ZnO-P₂O₅-B₂O₃ system glass was heat-treated at 660℃for 4h to precipitate fluorapatite（Ca₅（PO₄）₃F,FAP）nanocrystals,which greatly improved the fluorescence intensity.The absolute sensitivity of Tb³⁺/Eu³⁺doped fluorapatite glass ceramics is 1.90%K^-1 and the maximum relative sensitivity is 3.4%K^-1（753 K）under 378 nm near UV excitation.2.BaF₂-ZnO-P₂O₅-B₂O₃ system:The XRD patterns of Tb³⁺/Eu³⁺and Tb³⁺/Sm³⁺doped BaF₂-ZnO-P₂O₅-B₂O₃ system glasses show that the glass samples are all long-range disordered amorphous structures.Tb³⁺/Eu³ doped BaF₂-ZnO-P₂O₅-B₂O₃ system glass was heat-treated at 630℃for 4h to precipitate nano-fluorapatite（Ba₅（PO₄）₃F,B-FAP）.Tb³⁺/Eu³doped Ba₅（PO₄）₃F transparent glass ceramics are excited by 378 nm near-ultraviolet light,in the temperature range of 398-573 K,the maximum absolute sensitivity is 0.42%K^-1（398 K）,and the relative sensitivity is 3.4%K^-1.Tb³⁺/Sm³⁺doped BaF₂-ZnO-P₂O₅-B₂O₃system glass was heat-treated at 610℃for 4h to precipitate nano-fluorapatite（Ba₅（PO₄）₃F）.It can be seen from the spectral overlap between the absorption and emission spectra of Tb³⁺/Sm³⁺that the energy transfer ET of Tb³⁺/Sm³⁺in Ba₅（PO₄）₃F is from(Tb³⁺)donor to(Sm³⁺)acceptor.The Tb³⁺/Sm³⁺doped Ba₅（PO₄）₃F transparent glass ceramic has good temperature sensitivity in the temperature range of 298-573 K under the excitation of 378nm near-ultraviolet light.At 298K,the absolute sensitivity and relative sensitivity are both the largest maximum values,which are 0.36%K^-1 and 0.55%K^-1,respectively.3.CaF₂-ZnO-P₂O₅-Ca O-Si O₂ silicate system:the glass is heat-treated at 820℃for 4h to prepare transparent fluorapatite glass ceramics.The emission spectra of fluorapatite glass ceramic GC820 at different powers indicate that only two photons participate in the transitions(²H_11/2→⁴I_15/2),(⁴S_3/2→⁴I_15/2)and(⁴F_9/2→⁴I_15/2)and produce green and red UC emission.The energy transfer mechanism（ET）from Yb³⁺to Er³⁺is the most possible way for Er³⁺to up-convert the emission level.Yb³⁺/Er³⁺doped CaF₂-ZnO-P₂O₅-Ca O-Si O₂silicate system glass and Yb³⁺/Er³⁺doped fluorapatite glass ceramics have good temperature sensitivity in the temperature range of 303-678 K.The maximum absolute sensitivity of glass is 0.68%K^-1（678 K）,and the maximum relative sensitivity is 1.70%K^-1（303 K）.Yb³⁺/Er³⁺doped fluorapatite Ca₅（PO₄）₃F glass ceramics have a maximum Sa of 0.69%K^-1 at 678 K,and a maximum Sr of approximately 1.71%K^-1 at 303 K.The results show that Yb³⁺/Er³⁺-doped CaF₂-ZnO-P₂O₅-Ca O-Si O₂ silicate system glass and Yb³⁺/Er³⁺doped Ca₅（PO₄）₃F glass ceramics are potential materials for non-contact sensors.