1. by chemical solution process
2nd ENGE 2012 International Conference on Electronic Materials and Nanotechnology for Green Environment
Low-temperature synthesis and luminescence properties of alkaline-earth stannates phosphors prepared
by chemical solution process
Yong-Sang Jeon1, Young-Sun Jeon1, Seung-Dai Kim1, Seung Hwangbo2, Young-Hwan Lee3, Ju-Hyun Jeong4,
Tai-il Chol5, Jin-Tae Kim6, and Kyu-Seog Hwang1*
1Dept. of Biomed. Eng., Nambu Univ., 2Major in Photonic Eng., Honam Univ., 3Dept. of Automobile, Chunnam Techno College,
4Dept. of Ophthalmic Optics, Konyang Univ., 5Dept. of Photonic Eng., College of Eng., Chosun Univ., 6Dept. of Health Admin. Kwangju Women’s Univ.
Abstract
The Ca2SnO4:Re3+ (Re = Eu, Pr or Sm) phosphors prepared by sol-gel method at low temperature using a soluble inorganic salt. Mixed solution was pyrolyzed at 500℃ for 180 min in air. Final annealing was done at 800℃ for 180 min in air. The thermogravimetric-differential thermal analysis (TG-DTA) of the dried gels at 80℃ for 24 hrs was performed at 25 ~ 1000℃ to understand thermal decomposition process. Crystal structure and morphological variations were confirmed by an X-ray diffraction analysis and scanning electron microscope. The photoluminescence spectra were measured by a fluorescent spectrophotometer. Based on the crystallographical and surface morphological results, photoluminescence properties of rare-earth ion-doped Ca2SnO4 will be fully discussed.
Introduction
- Alkaline-earth stannates (CaSnO3) have received a considerable amount of attention over the past few years.
Ca2SnO4 is very easy to implant other ions into the host lattice and exhibit special luminescence properties. However, Ca2SnO4 can be prepared by convensional solid-state reaction at high temperature of 1300 ~ 1400℃.
Chemical solution process is an efficient technique for the preparation of phosphors; it has some advantages, such as good mixing of starting materials, relatively low reaction temperature and more homogeneous products.
- In this work, we report a red phosphor Ca2SnO4:Re3+ (Re = Eu, Pr or Sm) prepared by chemical solution process at lower temperature. The formation mechanism and luminescent properties were also investigated.
Processing
Sample Characterization
Thermogravimetric analysis (TGA) - DTG-60, Shimadzu, Japan - Decomposition and combustion of organics in starting sol
X-ray Diffraction (XRD) - D-Max-1200, Rigaku, Japan - Crystal structure of the annealed Ca2SnO4:Re3+(Re = Eu, Pr or Sm) powder Field Emission – Scanning Electron Microscope (FE-SEM) - S-4700, Hitachi, Japan - Surface morphology of the annealed Ca2SnO4:Re3+(Re = Eu, Pr or Sm) powder
Fluorescent Spectrophotometer - F4500, Hitachi, Japan - Excitation and emission spectra of the annealed Ca2SnO4:Re3+(Re = Eu, Pr or Sm) phosphors
Starting materials + Ethanol
Stirring for 30 min
Stirring for 180 min at 80C
Pyrolysis at 500C for 180 min in air
Annealing at 800C for 3 hrs in air
Experimental Results
TG-DTA Results
X-ray diffraction Results
:CaSnO3
:Unknown 
Ca2SnO4:Sm  
Intensity (arb.units)  
Ca2SnO4:Pr 
Ca2SnO4:Eu
2 (deg)
The TGA curve of the starting sol prepared by mixing- pyrolysis process.
XRD patterns of the Ca2SnO4:Re3+(Re = Eu, Pr or Sm) powders after annealing at 800℃.
FE-SEM Results
Luminescence Results
a) Ca2SnO4:Eu
b) Ca2SnO4:Pr
a) Ca2SnO4:Eu
a) Ca2SnO4:Eu
Ex = 314 nm
b) Ca2SnO4:Pr
b) Ca2SnO4:Pr
Ex = 314 nm
Intensity (arb.units)
Intensity (arb.units)
c) Ca2SnO4:Sm
c) Ca2SnO4:Sm
c) Ca2SnO4:Sm
Ex = 314 nm
Wavelength (nm)
Wavelength (nm)
FE-SEM images of Ca2SnO4:Re3+(Re = Eu, Pr or Sm) powders after annealing at 800℃.
Excitation spectra of Ca2SnO4:Re3+(Re = Eu, Pr or Sm) after annealing at 800℃.
Emission spectra of Ca2SnO4:Re3+(Re = Eu, Pr or Sm) after annealing at 800℃.
Conclusion
Ca2SnO4:Re3+ (Re = Eu, Pr or Sm) phosphors prepared by sol-gel method at low temperature using a soluble inorganic salt. The crystallographic and surface morphological results, photoluminescence properties of rare-earth ion-doped Ca2SnO4 will be fully discussed. The XRD pattern reveals that the samples single-phased and the doped various rare-earth ion have little influence on the host structure. The positions of the peaks in the XRD profiles shift to lower angles and some of the cell parameters increased.
The FE-SEM observation of the powder indicates that the sample has a bar-like shape and a little aggregation. The PL spectra at 314 nm near-UV excitation shows that four emission peak bands situated at 589, 613, 652 and 695 nm correspond to the characteristic transitions of Eu3+ from 5D07Fj (j = 1, 2, 3, and 4), namely the 5D07F1, 5D07F2, 5D07F3, and 5D07F4. The PL spectra at 314 nm near-UV excitation shows that the emission peak at 488, 540 and 626 nm are attributed to the transitions 3P03H4, 3P03H5 and the 1D23H4,6, respectively.