CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

More documents

Recommendations

Info

All the samples show three bands centered around 345, 482 and 675 cm -1 . The peak width increases with increase in Eu concentration and this has been assigned to the increased distortion in the Ga 2 O 3 lattice brought about by Eu 3+ incorporation. The bands also shifted towards lower wave numbers for the samples doped up to 0.75 at % Eu 3+ (for the samples doped above 0.75 at %, the peak is so broad that shifting of the peak maxima could not be clearly observed). This can be explained based on the difference in the mass of gallium and lanthanide ions. Red shift in the peak maxima can be explained based on the heavier mass of Eu 3+ ions compared to Ga 3+ ions, indicating the formation of Ga-O-Eu type of linkages. Increase in broadening of the IR peaks beyond 0.75 at% is due to the conversion of crystalline Ga 2 O 3 to an amorphous gallium oxide phase. However, samples heated at 900°C show the crystalline nature beyond 1 at % lanthanide ions doping (Fig.35). For the samples doped with 3 at % or more Eu 3+ , a small peak started appearing at 2θ value of 28.4° and 32.2°. These peaks are attributed to Eu 2 O 3 . Unit cell parameters are calculated by least square fitting of XRD patterns of 900°C heated samples (Table 3). * * 5 at % Eu (11 nm) Intensity (arb.units) * * 3 at % Eu (14 nm) 1 at % Eu (16 nm) 0.75 at % Eu (18 nm) 0 at% Eu (19 nm) 20 30 40 50 60 70 2θ/ o Fig.35. XRD patterns of β-Ga 2 O 3 doped with 0, 0.75, 1, 3 and 5 at % of Eu 3+ (peak marked * correspond to Eu 2 O 3 ). Values in brackets show average crystallite size. 78
The cell parameters increases with increase in the lanthanide ion concentration up to 0.75 at % and above that they started decreasing. Although, lattice parameters start decreasing, they are larger than the undoped sample. From the above results, it is inferred that lanthanide ions are replacing Ga 3+ ions up to 0.75 at % and above that a separate phase namely Eu 2 O 3 is formed. The average crystallite size calculated by using Scherrer formula for samples doped with different percentage of lanthanide ions are given in the Table 3. The average crystallite size decreases with increase in the lanthanide ions concentration. To confirm this fact, TEM measurements were carried out and the results are discussed below. Table.3. Variation in the lattice parameters of β-Ga 2 O 3 samples prepared in presence of different amounts of Eu 3+ ions. Numbers in bracket indicate the errors. at % Eu 3+ Avg. Crystal β-Ga 2 O 3 size (nm) a (Å) b (Å) c (Å) β (°) Cell volume (Å 3 ) 0 19 12.237(1) 3.031(2) 5.802(2) 103.865(3) 208.93(2) 0.5 19 12.242(2) 3.038(1) 5.809(3) 103.940(2) 209.70(1) 0.75 18 12.249(1) 3.042(3) 5.820(2) 104.018(2) 210.40(2) 1 16 12.249(2) 3.039(2) 5.812(1) 104.012(1) 209.94(2) 2 15 12.242(2) 3.038(3) 5.809(2) 103.875(2) 209.67(3) 3 14 12.240(3) 3.038(1) 5.810(1) 104.077(3) 209.60(3) 5 11 12.210(2) 3.038(2) 5.807(2) 103.969(3) 209.04(2) Figure 36 shows the TEM images of 900°C heated samples containing different concentrations of Eu 3+ ions. The shape and size of the Ga 2 O 3 nanomaterials changed after doping with lanthanide ions. Undoped Ga 2 O 3 shows uniform nanorods with length 2.3-2.8 mm and width 0.2-0.3 mm. whereas 0.75 at % Eu doped samples exhibit the formation of both nanorods and nanoparticles with a broad size distribution. For the Ga 2 O 3 samples with 3 at % Eu 3+ ions, only nanoparticles with irregular shapes are observed instead of nanorods. The size of the nanoparticles is further reduced on increasing the Eu 3+ concentration to 5 at %. This can be explained based on structural changes taking place in GaOOH lattice after doping with 79
Page 1 and 2:
SYNTHESIS AND CHARACTERIZATION OF L
Page 3 and 4:
STATEMENT BY AUTHOR This dissertati
Page 5 and 6:
Dedicated to ……… My beloved b
Page 7 and 8:
also thankful to all the members of
Page 9 and 10:
2.3 Synthesis of binary oxide nanom
Page 11 and 12:
CHAPTER 5: Zinc Gallate ...........
Page 13 and 14:
imaging, scintillators, lasers, etc
Page 15 and 16:
morphology by heating at 500 and 90
Page 17 and 18:
nanoparticles having hexagonal stru
Page 19 and 20:
100°C and 185°C, respectively in
Page 21 and 22:
into poly methyl methacryllate (PMM
Page 23 and 24:
3. N. M. Dimitrijevic, Z. V. Saponj
Page 25 and 26:
Fig.13: Fig.14: (a) Simplified ray
Page 27 and 28:
Eu 3+ ions after heat treatment at
Page 29 and 30:
615 nm Fig.50: FT-IR patterns (a) a
Page 31 and 32:
area electron diffraction pattern a
Page 33 and 34:
different amounts of Eu 3+ . Fig.86
Page 35 and 36:
and 545 nm, respectively. Fig.106:
Page 37 and 38:
List of Tables: Table 1: Variation
Page 39 and 40:
CHAPTER 1: Introduction 1.1 Histori
Page 41 and 42:
Rods, cylinders, wires and tubes ar
Page 43 and 44:
must be supersaturated either by di
Page 45 and 46:
- + - + charge stabilized nanoparti
Page 47 and 48:
exothermic reaction between the met
Page 49 and 50:
constant, ħ is h/2π, e is the ele
Page 51 and 52:
these platinum complexes have been
Page 53 and 54:
(IR), visible and ultra-violet (UV)
Page 55 and 56:
in Ce 3+ , Pr 3+ , Tb 3+ and CT abs
Page 57 and 58:
assisted by lattice phonons of appr
Page 59 and 60:
decay-time reduction is much easier
Page 61 and 62:
nanocrystals is shown in Fig.10 [58
Page 63 and 64:
depends strongly on the nature of t
Page 65 and 66: corresponding emission and excitati
Page 67 and 68: doped nanomaterials of the above me
Page 69 and 70: will be formed and subsequently it
Page 71 and 72: Eu 3+ ions were also subjected to s
Page 73 and 74: transferred into a two-necked RB fl
Page 75 and 76: Where λ is the wavelength of X-ray
Page 77 and 78: Micro-structural characterization b
Page 79 and 80: electrons (i.e. diffraction mode).
Page 81 and 82: diffraction spots. By tilting a cry
Page 83 and 84: surface. The contact mode can obtai
Page 85 and 86: three types lines in the scattered
Page 87 and 88: solids tend to be broadened because
Page 89 and 90: sample fluoresce. The fluorescent l
Page 91 and 92: pulse frequency) as excitation sour
Page 93 and 94: Lanthanide ions doped Ga 2 O 3 nano
Page 95 and 96: atoms at three corners and the lone
Page 97 and 98: Figure 19 (a-d) shows SEM images of
Page 99 and 100: Based on these results, it can be i
Page 101 and 102: almost normal to the equatorial pla
Page 103 and 104: Table 2. Summary of important modes
Page 105 and 106: systematic disappearance of these t
Page 107 and 108: comparison, Eu 3+ ions alone in wat
Page 109 and 110: the samples, suggesting that Eu 3+
Page 111 and 112: These inferences are further substa
Page 113 and 114: Similar DTA peaks have been reporte
Page 115: GaOOH samples doped with different
Page 119 and 120: strong emission compared to corresp
Page 121 and 122: curves are shown in Fig.39. Lifetim
Page 123 and 124: Similar results are also observed f
Page 125 and 126: intensity of XRD peaks correspond t
Page 127 and 128: compared to the bulk material and a
Page 129 and 130: is almost 1½ times that of peak B1
Page 131 and 132: 3.8 Interaction of Eu 3+ ions with
Page 133 and 134: The spectrum shows strong emission
Page 135 and 136: The decay curves are found to be bi
Page 137 and 138: As prepared undoped Sb 2 O 3 sample
Page 139 and 140: Intensity(arb.units) 1.0 0.8 0.6 0.
Page 141 and 142: 3+ having surface lanthanide ions.
Page 143 and 144: diffraction patterns from the GaPO
Page 145 and 146: 5 D 0 7 F 2 level to 7 F 7 7 1 , F
Page 147 and 148: The second possibility is the excha
Page 149 and 150: chemical shift anisotropy is much h
Page 151 and 152: not have strong interaction with th
Page 153 and 154: (001) (110) (011) (101) (020) (101)
Page 155 and 156: growth centre compared to higher vi
Page 157 and 158: observed after excitation at 250 an
Page 159 and 160: 3+ 3+ concentration quenching. Tb l
Page 161 and 162: Compared to the selected area elect
Page 163 and 164: lattice. Lanthanide ions occupying
Page 165 and 166: obtained after 275 nm excitation is
Page 167 and 168:
The luminescence dynamics associate
Page 169 and 170:
that the broad peak can be resolved
Page 171 and 172:
espectively. Value of this integral
Page 173 and 174:
ethylene glycol moiety (stabilizing
Page 175 and 176:
Room temperature and 100°C synthes
Page 177 and 178:
heavier metal ion as compared to La
Page 179 and 180:
Similar studies were also carried o
Page 181 and 182:
3+ 3+ faster decay component is ass
Page 183 and 184:
the other hand the Eu 3+ lifetime h
Page 185 and 186:
3+ 4.4.8 Luminescence studies on Sm
Page 187 and 188:
CHAPTER 5: Zinc gallate (ZnGa 2 O 4
Page 189 and 190:
In pure EG an amorphous product is
Page 191 and 192:
water content in the reaction mediu
Page 193 and 194:
nucleation, thereby leading to incr
Page 195 and 196:
particles. Thus the TEM studies als
Page 197 and 198:
value. The lattice parameters calcu
Page 199 and 200:
Quantum yield of the blue emission
Page 201 and 202:
5.5.2. Eu 3+ doped ZnGa 1.5 In 0.5
Page 203 and 204:
CHAPTER 6: Tungstates [MWO 4 (M = C
Page 205 and 206:
ionic radius of the metal cation ca
Page 207 and 208:
lattice. Asymmetric ratio is ~ 12 f
Page 209 and 210:
700 Intensity (arb.units) 600 λ ex
Page 211 and 212:
Intensity (arb.units) 25000 20000 1
Page 213 and 214:
Strong green emission has been obse
Page 215 and 216:
consists of strong band at 255 nm a
Page 217 and 218:
peak can be attributed to the cryst
Page 219 and 220:
nm) is observed from Er 3+ doped Ga
Page 221 and 222:
and Dy 3+ doped CaWO 4 nanoparticle
Page 223 and 224:
REFERENCES 1. D. J. Barber, I. C. F
Page 225 and 226:
32. K. A. Gschneidner, Jr., L. Eyri
Page 227 and 228:
65. Z. Deng, F. Tang, D. Chen, X. M
Page 229 and 230:
100. A. Rouanel, J. J. Serra, K. Al
Page 231 and 232:
130. F. Li, W. Jianhuai, L. Jiongti
Page 233 and 234:
166. L. Fu, Z. Liu, Y. Liu, B. Han,
Page 235 and 236:
205. R. Sasikala, V. Sudarsan, C. S
Page 237 and 238:
238. E. Oldfield, R. A. Kinsey, K.
Page 239 and 240:
271. B. G. Hyde, S. Andersson, ”I
Page 241 and 242:
B. S. Naidu, B. Vishwanadh, V. Suda
Page 243:
9. Room temperature synthesis of mu
show all

CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?