Research Of Agricultural Light Conversion Materials Based On 3CaO-2SiO₂-CaF₂ Glass

facility agriculture has become an important part of modern agricultural industry With the increasing demand for agricultural industrialization and the continuous development of modern agricultural science and technology.It has developed and applied rapidly as the focus of agricultural development in various countries.Glass greenhouse that can adjust the light environment to control plant life activities is an important technology in the field of modern plant cultivation.Because of the using silica gel and organic resin,the traditional agricultural conversion materials,such as optical conversion film and LED plant growth lamp,have many practical problems.Due to the low thermal conductivity and poor thermal stability of organic resin and silica gel,the yellowing and aging rate will be significantly accelerated due to the working environment and temperature during long-term use,which will eventually lead to the drift of luminous color coordinates of light conversion materials and shorten the actual service life.Therefore,it is a meaningful work to develop the light conversion glass,which can control the sunlight wavelength to develop solar energy effectively.In this paper,a new type of 3Ca O-2Si O₂-Ca F₂ glass was prepared by traditional melting method.The luminescence properties of 3Ca O-2Si O₂-Ca F₂ glasses doped with rare earth ions and transition metal ions were prepared and studied to discuss the changes of optical properties of doped luminescent ions with different concentrations.The energy transfer between ions was studied by preparing and studying3Ca O-2Si O₂-Ca F₂ glasses codoped with rare earth ions and transition metal ions.The3Ca O-2Si O₂-Ca F₂ glass ceramics were prepared by heat treatment.The effects of heat treatment on luminescence and energy absorption of different doped luminescent ions glasses were studied.According to the light demand of plant photosynthesis,the main research contents are as follows:（1）Eu³⁺doped 3Ca O-2Si O₂-Ca F₂ glasses were successfully prepared with no crystallization occurred,indicating that the high doping solubility of the glass.Eu³⁺in the sample can be excited by ultraviolet and blue light in the range of 355-420nm,emit strong red light,and form a wide emission band in the range of 570-640nm.Due to the f→f transition of Eu³⁺,the doping concentration has little effect on the luminescence properties.（2）Ce³⁺and Eu²⁺doped glasses were successfully prepared.Ce³⁺doped glass samples can be effectively excited by UV and near-UV light in the range of 230-400nm,emit strong blue light in the range of 350-550nm.Eu²⁺doped glass samples can be effectively excited by blue light,UV light and near-UV light in the range of280-500 nm,and form a wide yellow green light emission band in the range of450-750 nm.With the increase of the concentration of doped Ce³⁺and Eu²⁺,the emission spectra have a regular red shift trend,which shows that light conversion glass materials with adjustable emission spectra can be prepared by adjusting the concentration of doped Ce³⁺and Eu²⁺.（3）Mn⁴⁺and Mn²⁺doped glasses were successfully prepared.Both Mn⁴⁺and Mn²⁺ can be effectively excited by near ultraviolet and blue light in the range of 330-600nm,and form a wide red emission band in the range of 500-850 nm.The luminescence intensity of Mn²⁺doped glass samples is higher than Mn⁴⁺doped glass.Mn²⁺doped glass samples also have a red shift trend with the increase of doping concentration.（4）The 3Ca O-2Si O₂-Ca F₂ glasses co-doped with Eu²⁺/Mn²⁺and Ce³⁺/Mn²⁺were successfully prepared.Under 350 nm excitation,the energy transfer efficiency between Ce³⁺and Mn²⁺increases with the increase of Mn²⁺doping concentration,and there are wide blue and red emission peaks in the overall emission spectrum.Under400 nm excitation,the energy transfer efficiency between Eu²⁺and Mn²⁺also shows an upward trend,and the overall emission spectrum shows a widening trend.When doped with 1.0mol%Mn²⁺,the FWHM of the overall emission spectra reaches267nm,has strong emission in both yellow and red light（5）Different ions doped glass ceramics were prepared by heat treatment,all glass samples had good transparency.After heat treatment,Ca F₂ crystals were precipitated from all glass ceramics samples,and the luminous ions were enriched to Ca F₂microcrystals.Because the d→d transition of Eu³⁺is less affected by the matrix,glass ceramics has little effect on the luminescence properties.The excitation and emission spectra of Ce³⁺and Eu²⁺doped glasses show an obvious blue shift trend.These results show that rare earth ions effectively enter Ca F₂ crystallites.Because of the stronger crystal field and lower phonon energy of Ca F₂,rare earth ions have higher luminescence intensity and excited state lifetime due to the reduced non radiation loss and multi phonon relaxation of rare earth ions.The excitation and emission spectra of Mn⁴⁺and Mn²⁺doped glasses did not change significantly after heat treatment.The results show that although transition metal ions can effectively enter the Ca F₂ lattice position,the formation of a small amount of lattice can not change the whole matrix environment of transition metal ions,which make the changes of luminescence and lifetime not obvious.