목차
1. 서론 1
2. 형광체의 장/단범위 구조분석법 원리 2
2.1. 장범위 구조분석법: Rietveld refinement 2
2.1.1. X-ray와 중성자 회절을 이용한 형광체의 구조분석 2
2.1.2. Maximum entropy method (MEM) 분석법 3
2.2. 단범위 구조분석법 3
2.2.1. Pair distribution function (PDF) 분석법 3
2.2.2. Extended X-ray absorption fine structure (EXAFS) 분석법 4
2.2.3. 핵자기 공명 분광법 (nuclear magnetic resonance, NMR) 4
3. 형광체의 장/단범위 구조분석 적용 5
3.1. Cs3CoCl5 구조의 형광체 5
3.2. Bredigite 구조의 형광체 연구 7
4. 결론 9
참고문헌 10
Table 1. Inter - atomic Distances of Both Mg - O Polyhedrons and Bond Valence Sums (BVS) Found in Ca13.7 Eu0.3 Mg1.7 Mn0.3 [SiO4]8 at Room Temperature 8
Fig. 1. Principle of Rietveld refinement using least-square minimization. 2
Fig. 2. Nuclear scattering lengths for thermal neutrons depending on the atomic weight. 3
Fig. 3. Simulation result of pair distribution function. (a) structure of graphene. Each r₁, r₂, r₃ represents 1st nearest-neighbor(NN), 2nd NN, 3rd NN distance. (b) PDF Result: r₁, r₂, and r₃ mean inter-atomic distances in structure of graphene. 4
Fig. 4. EXAFS region of X-ray absorption spectrum. 4
Fig. 5. Diffuse reflectance absorption, luminescence excitation, and luminescence emission spectra of La0.975Ce0.025Sr2AlO5. The intensity scale is linear and has been normalized. The absorption spectrum was obtained by Kubelka-Munk transformation of the optical reflectance. 5
Fig. 6. (a-c) MEM isosurface of the electron density depicted within the unit cell of LSA:Ce3+. (a) depicts a projection down the a axis of the unit cell, and (b) depicts a projection down the c axis, showing the plane containing the 8h site with (La/Sr1/Ce) with O1 at the center and corners.... 5
Fig. 7. Excitation and emission spectra of (i) SBAF:Ce3+ (x = 1.0) at room temperature compared with a (ii) com-mercial YAG:Ce3+ phosphor. 6
Fig. 8. Views of the structures of end-member compounds in the solid solution series viewed down the [010] direction of the unit cell: (a) Sr₃AlO₄F and (b) Sr3SiO5. Light grayspheres are Sr2 and dark grey spheres in (a) show amixed Sr2 site.... 6
Fig. 9. Mean Sr-O/F atomic distances obtained from Rietveld refinements of different Sr2.975Ce0.025Al1-xSixO4+xF1-x materials(x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) for each Sr1 and Sr2 polyhedron: (a) Sr1-O/F and (b) Sr2-O/F. Number of bonds are given in parentheses. 7
Fig. 10. Rietveld refinement of the powder X-ray diffraction profile of Ca13.7Eu0.3Mg2[SiO4]8. Data (points) and fit (lines), the difference profile, and expected reflection positions are displayed. Unit cell representation of the crystal structure of Ca14Mg2[SiO4]8 (CMS).... 7
Fig. 11. (a) XRD patterns of Ca13.7Eu0.3Mg2[SiO4]8 (CMS:Eu2+) and Ca13.7Eu0.3Mg1.7Mn0.3[SiO4]8 (CMS:Eu2+, Mn2+). The panel on the bottom displays the expected reflection positions for the CMS. (b) Rietveld refinement of the powder X-ray diffraction profile of Ca13.7Eu0.3Mg1.7Mn0.3[SiO4]8.... 8
Fig. 12. Rietveld refinement patterns of Ca13.7Eu0.3Mg2Si8O28+δ N4-δ (CMSN:Eu2+) using (a) neutron and (b) X-ray powder diffraction data. Black circle marks represent the observed intensities, and the solid line defines calculated intensities. A difference (obs.-cal.) plot is shown beneath. 9
Fig. 13. Si solid-state MAS NMR spectra of (a) CMS:Eu2+ and (b) CMSN:Eu2+. 9