The calcium sulfate double salt Na_4Ca(SO_4)_3 was prepared by high temperature synthesis method. The modern instruments such as XRD, TG-DTA and SEM etc., were used to research the processing steps of the double salt. The experimental results show the reaction steps were described as follows: CaSO_4+Na_2SO_4→(Na_(0.8)Ca_(0.1))2SO4→Na_4Ca(SO_4)_3. Na_4Ca(SO_4)_3 is a steady phase at high temperature. Optimal synthesis temperatures range is 800 ℃~1 100 ℃. Effect of incubation temperature and time on morphology of double salt was discussed. The crystal grows better when it is synthesized at 1000 ℃ for 2 h and then incubated at 945 ℃ for 5 h.
In this study, we present a novel layered material (LEuH-TTA) consisting of layered europium hydroxide (LEuH) and organic sensitizer 2-thenoyltrifluoroacetone (TTA) in a simple and environmental benign way and it was characterized by FT-IR and XRD. The luminescence intensity of LEuH-TTA increased significantly after modified with TTA, almost 8 times that of LEuH at 612 nm. The luminescence behavior of LEuH-TTA was investigated by luminescence analysis, the results showed that red emission is caused by energy transfer from the TTA ligand to the coordinated Eu3+ ions. Furthermore, the thickness of luminescence film was measured and the SEM showed that it is about 1 μm.
PVP/[Gd( NO3) 3 + Ga( NO3) 3 + Eu( NO3) 3]composite nanobelts were prepared via electrospinning,and Gd3Ga5O12∶ Eu3 + ( denoted as GGG∶ Eu3 + for short) porous luminescent nanobelts were fabricated by calcination of the prepared composite nanobelts. The samples were characterized by XRD,SEM,TEM, TG-DTA,FTIR and fluorescence spectroscopy. XRD results show that the composite nanobelts are amorphous in structure,and pure phase GGG∶ Eu3 + nanobelts were obtained by calcination of the relevant composite nanobelts at 800 ℃ for 8 h and GGG∶ Eu3 + nanobelts belong to cubic system with space group Ia3d. SEM analysis indicates that the surface of as-prepared composite nanobelts is smooth,the widths of the composite fibers are in narrow range,and the mean width and thickness are ca. 10 μm and ca. 100 nm,respectively, and there are no cross-linkages among nanobelts. The width and thickness of GGG∶ Eu3 + nanobelts are ca. 2. 5 μm and ca. 30 nm,respectively,and the length is greater than 500 μm. TEM analysis indicates that GGG∶ Eu3 + nanobelts possess porous,web-like and polycrystalline structure. TG-DTA analysis reveals that DMF,organic compounds and nitrate salts in the composite nanobelts are decomposed and volatilized totally, and the mass of the sample kept constant when sintering temperature was above 700 ℃,and the total mass loss percentage is 93. 1% . FTIR analysis manifests that pure inorganic oxides are formed at 800 ℃. Fluorescence spectroscopy results show that GGG∶ Eu3 + nanobelts emit strong red emission centering at 591 nm under the excitation of 254 nm ultraviolet ray,which is attributed to the transition of 5D0→7F1 energy levels of Eu3 + . The possible formation mechanism of the GGG∶ Eu3 + nanobelts was preliminarily discussed. This technique can be applied to fabricate other rare earth garnet-typed nanobelts.
H_2Ti_4O_9 nanocrystals with high specific surface areas were prepared by delamination and precip- itation process through ball milling combined with ion exchange reaction.The samples were characterized by X-ray powder diffraction,transmission electron microscope,thermal analysis,N_2 adsorption-desorption isotherm, and absorption spectrum.The crystallites of Ti_4O_9~(2-) in the form of titania nanosheets have lateral size less than 50nm.The specific surface area of H_2Ti_4O_9 nanocrystals depends on pH values of precipitation solution and ball milling time.The specific surface area of H_2Ti_4O_9 nanocrystals prepared by ball-milling of K_2Ti_4O_9 for 2h and suspending in 1mol/L HCl followed by precipitation at pH=8 can reach 328.4m~2·g~(-1).
PVA/[Gd(NO3)3+Yb(NO3)3+Er(NO3)3] composite nanofibers were fabricated by the combination of sol-gel method and electrospinning.Gd2O3:Yb3+,Er3+ upconversion nanofibers were obtained by the calcination of relevant composite nanofibers.The samples were characterized by using XRD,SEM,TG-DTA,FTIR and fluorescence spectroscopy techniques.The results show that the composite nanofibers are amorphous in structure,and Gd2O3:Yb3+,Er3+ upconversion nanofibers are cubic in structure with space group Ia3.The mean diameter of the composite nanofibers is 140nm.The Gd2O3:Yb3+,Er3+ upconversion nanofibers of 60nm in average diameter were acquired at 600℃.The water,organic compounds,nitrates in the composite nanofibers are decomposed and volatilized totally,and the weight of the sample keeps constant when sintering temperature is above 600℃,and the total weight loss percentage is 81%.The FTIR spectrum of the composite nanofibers is basically the same as that of the pure PVA,and Gd2O3:Yb3+,Er3+ upconversion nanofibers are formed above 600℃.In the excitation of a 980 nm continuous wave diode laser,the Gd2O3:Yb3+,Er3+ nanofibers emitt strong green and red upconversion emissions centered at 522nm,560nm and 659nm,respectively.The green emissions are attributed to the transitions of 2H11/2/4S3/2→4Il5/2 energy levels of Er3+ ions,and the red emission is assigned to the transition of 4F9/2→4Il5/2 energy levels of Er3+ ions.In the course of Gd2O3:Yb3+,Er3+ upconversion nanofibers formation,PVA acts as an oriented template.When the composite nanofibers are sintered,PVA is decomposed and evaporated,and rare earth nitrates are also decomposed and oxidized and then Gd2O3:Yb3+,Er3+ nanoparticles are formed.And these nanoparticles are mutually connected to form the Gd2O3:Yb3+,Er3+ upconversion nanofibers.
We incorporated carbon dots (CDs) into a SrAl2O4:Eu,Dy phosphor (SAO), and made use of the dual emission from the CDs and SAO within such a composite to realize ratiometric temperature sensing from 100 to 400 K.
The surface segregation of La 2O 3 in Mo La 2O 3 cathode was carried out by Auger electron spectroscopy. Lanthanum and oxygen ions (La 3+ and O 2- ) diffuse from the grain boundaries to the surface respectively, and these ions recombine into La 2O 3 molecules on the surface. The results were analyzed by kinetics of grain boundary diffusion. In the temperature range of 1 123～1 423 K, the diffusion coefficients of La 3+ and O 2- ions were found to fit with the following equations: D La =3.670 3×10 -16 exp(-1.016 39×10 5/ RT ) D O=1.512 2×10 -16 exp(-8.130 66×10 4/ RT ). [
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