Long afterglow materials release energy in the form of prolonged continuous emission after the excitation source stops.The mechanism of persistent luminescence of long afterglow materials is different from that of fluorescent materials.The process of persistent luminescence involves the capture,storage and release of charge carriers by traps.ZnGa2O4 has the advantages of stable chemical properties,wide band gap(4.4~4.8 e V),easy doping,etc.A large number of reports have confirmed that ZnGa2O4 is a good long afterglow matrix.Especially,the Cr-doped ZnGa2O4 system shows excellent performance and great potential.At present,the research of long afterglow materials is still limited to the form ofpowders.In the face of the harsh environment in the actual applications,long afterglow transparent ceramics which have high strength,high temperature resistance,good wear resistance,acid and alkali corrosion resistance and other characteristics,have a wider range of application scenarios.The performance of the long afterglow transparent ceramics is superior to the form of powders.The macroscopic tuning of the afterglow properties can be achieved by changing the volume size of the long afterglow transparent ceramics(the external excitation light can penetrate the sample,thus inducing the formation of the carrier inside the transparent ceramics).In order to give full play to the advantages of long afterglow transparent ceramics,a series of high transmittance ZnGa2O4-based long afterglow ceramics were successfully prepared in this work.The main content of this work includes the following aspects:(1)Starting from the preparation of pure ZnGa2O4 powders by co-precipitation method,the effect of different dosage of precipitator on the powders of ZnGa2O4 was systematically studied.The powders with pure phase of zinc gallate and average particle size of 43 nm was synthesized by ammonium carbonate precipitator solution with concentration of 0.5 mol/L.The powders will be formed by 20 MPa dry pressing and250 MPa cold isostatic pressing.The molded green body was pre-sintered at 1150℃for 5 h in a muffle furnace.The 0.5 at.%Cr:ZnGa2O4 ceramics pre-sintered by air were treated with HIP at 200 MPa in an argon atmosphere of 1100℃×3 h.0.5 at.%Cr:ZnGa2O4 long afterglow transparent ceramics were successfully prepared for the first time.The in-line transmittance of the long afterglow transparent ceramics at 800nm is 66.4%(1.3 mm thick),and the average grain size is 515 nm.Ceramics can be effectively excited at 200 nm to 650 nm to generate a peak of 700 nm near infrared light narrowband emission.After HIP,the transparent ceramics produced the visible afterglow attenuation for tens of minutes after sunlight excitation(>0.32 mcd/m2).(2)Using the same technological process,ZnGa2O4 transparent ceramics doped with different concentrations of Cr3+were prepared.A certain amount of Cr3+doping can improve the optical quality of Cr:ZnGa2O4 ceramics.The in-line transmittances of 0.5at.%,0.75 at.%,1.0 at.%and 1.25 at.%ZnGa2O4 transparent ceramics at 800 nm are60.1%,66.3%,69.3%and 66.4%(1.3mm thick)respectively.The average grain size of HIP post-treated ceramic samples is about 700 nm.The ceramics before and after HIP can be effectively excited from 200 nm to 650 nm to produce red light.The 1.0 at.%Cr doped ZnGa2O4 transparent ceramics showed the best afterglow performance.The fast decay lifetimeτ1 and slow decay lifetimeτ2are 62.2 s and 1290.5 s,respectively.(3)Cr,Bi:ZnGa2O4 ceramics were prepared by introducing Bi3+as co-doped ion.The excitation peak shape of Cr,Bi:ZnGa2O4 ceramics is consistent with that of ZnGa2O4ceramics with single doping of Cr,and can be effectively excited by the light at 200 nm to 650 nm to produce red emission.Bi3+doping does not significantly improve the afterglow properties of Cr,Bi:ZnGa2O4 ceramics,and Bi3+doping is not conducive to the transparency of ceramics.(4)1 at.%Eu:ZnGa2O4 long afterglow transparent ceramics were prepared.The average grain size of the HIP post-treated ceramics is 1.5μm,and there are some long and narrow pores inside the ceramic,and the second phase can be seen obviously.The second phase may be Eu2O3.The in-line transmittance of the ceramics at 800 nm is14.5%(1.3 mm thick).The afterglow properties of HIP post-treated ceramics did not improve.(5)0.1 at.%Bi:ZnGa2O4 long afterglow transparent ceramics were prepared.The average grain size is 700-800 nm.At 800 nm the in-line transmittance is 63%(1.3 mm thick).However,the afterglow performance of transparent ceramics is poor due to the presence of internal impurities.(6)2 at.%Dy:ZnGa2O4 long afterglow transparent ceramics were prepared.There are some pores in 2 at.%Dy:ZnGa2O4 transparent ceramics,the grain size distribution is not uniform,and there is obvious second phase Dy2O3.The in-line transmittance of2 at.%Dy:ZnGa2O4 transparent ceramics at 800 nm is 47.9%(1.3 mm thick).The persistent luminescence of transparent ceramics is improved compared with that of pre-sintered ceramics. |