CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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and constitutional hydroxyl groups respectively present with GaOOH samples. The weight loss is around 9% in the range of 350 to 420°C, confirming the dehydration from GaOOH phase [27]. Such dehydration processes are characterised by endothermic peaks around 230 and 400°C in the corresponding DTA pattern. Beyond 420°C, there is no significant change in the weight with increase in temperatures as is clear from the straight line with negligible slope observed beyond 420°C in the TG pattern shown in Fig.30 (a). However, the DTA pattern showed a broad exothermic peak in the region 640 to 1040°C. This is due to the conversion of α-Ga 2 O 3 phase to β-Ga 2 O 3 . Heat flow (μV) 1.0 0.5 0.0 -0.5 TG DTA 4 2 0 -2 -4 -6 -8 Weigth loss (%) Heat flow (μV) 0 -1 -2 -3 TG DTA 2 0 -2 -4 -6 -8 Weigth loss (%) -1.0 (a) 200 400 600 800 1000 Temperature (°C) -10 -4 (b) 200 400 600 800 1000 Temperature (°C) -10 Heat flow (μv) 1 0 -1 -2 TG (c) DTA 200 400 600 800 1000 Temperature (°C) 2 0 -2 -4 -6 -8 -10 -12 Weigth loss (%) Heat flow (μV) -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 TG DTA 200 400 600 800 1000 Temperature (°C) Fig.30. TG-DTA patterns of GaOOH nanorods prepared in presence of (a) 0 at % (b) 0.5 at % (c) 0.75 a t% and (d) 1 at % Eu 3+ ions. (d) 2 0 -2 -4 -6 -8 -10 -12 -14 Weigth loss (%) 74
Similar DTA peaks have been reported earlier [189, 192] for decomposition of GaOOH. The GaOOH sample prepared in presence of 0.5 at % Eu 3+ ions (Fig.30 (b)), both TG and DTA patterns are essentially similar to that of GaOOH nanorods shown in Fig.30 (a). However, the DTA peaks are slightly broadened for the Eu 3+ containing sample as can be seen from Fig.30 (b). Broadening of the peak has been attributed to distortion taking place with the Ga-O bonds associated with Ga-OH linkages brought about by its interaction with Eu 3+ ions. The percentage loss of weight is found to be around 9% over the region of 230 to 400°C, which is characteristic of the dehydration process in GaOOH. The initial dehydration step in the region 200-280°C is more predominant for GaOOH sample prepared with 0.75 at % Eu 3+ ions (Fig.30 (c)) as compared to the corresponding step for the GaOOH sample prepared with 0.5 at % Eu 3+ . In addition to this, the weight loss below 400°C is ~10 %, suggesting that another hydroxide species along with GaOOH phase is present with the sample. This is namely the Ga(OH) 3 phase formed by the collapse of a part of the layered GaOOH structure. But the DTA pattern is comparable with that of GaOOH sample prepared with 0.5 at % Eu 3+ . For GaOOH sample prepared with 1 at % Eu 3+ ions, both DTA and TG patterns significantly changed (Fig.30 (d)). The weight loss of ~12% is indicative of an increase in the extent of gallium hydroxide phase along with the GaOOH phase. The DTA pattern (Fig.30 (d)) is similar to that obtained for a group 13 metal hydroxides like In(OH) 3 [202, 203] and can be considered as overlapping of the DTA patterns of Ga(OH) 3 and GaOOH present in the sample. From these results it is inferred that GaOOH undergo complete decomposition in the presence of Eu 3+ ions at a concentration >1 at % forming Ga(OH) 3 species. Hence the TG-DTA results are in conformity with the inferences drawn from XRD and photo luminescence studies. 3.4. Effect of heat treatment on crystal phase and morphology of Ga 2 O 3 and Ga 2 O 3 :Ln 3+ nanomaterials: GaOOH nanorods on heating get converted to rhombohedral α-Ga 2 O 3 at 75
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SYNTHESIS AND CHARACTERIZATION OF L
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STATEMENT BY AUTHOR This dissertati
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Dedicated to ……… My beloved b
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also thankful to all the members of
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2.3 Synthesis of binary oxide nanom
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CHAPTER 5: Zinc Gallate ...........
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imaging, scintillators, lasers, etc
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morphology by heating at 500 and 90
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nanoparticles having hexagonal stru
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100°C and 185°C, respectively in
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into poly methyl methacryllate (PMM
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3. N. M. Dimitrijevic, Z. V. Saponj
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Fig.13: Fig.14: (a) Simplified ray
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Eu 3+ ions after heat treatment at
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615 nm Fig.50: FT-IR patterns (a) a
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area electron diffraction pattern a
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different amounts of Eu 3+ . Fig.86
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and 545 nm, respectively. Fig.106:
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List of Tables: Table 1: Variation
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CHAPTER 1: Introduction 1.1 Histori
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Rods, cylinders, wires and tubes ar
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must be supersaturated either by di
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- + - + charge stabilized nanoparti
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exothermic reaction between the met
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constant, ħ is h/2π, e is the ele
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these platinum complexes have been
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(IR), visible and ultra-violet (UV)
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in Ce 3+ , Pr 3+ , Tb 3+ and CT abs
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assisted by lattice phonons of appr
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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: These inferences are further substa
Page 115 and 116: GaOOH samples doped with different
Page 117 and 118: The cell parameters increases with
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
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lattice. Lanthanide ions occupying
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obtained after 275 nm excitation is
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The luminescence dynamics associate
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that the broad peak can be resolved
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espectively. Value of this integral
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ethylene glycol moiety (stabilizing
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Room temperature and 100°C synthes
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heavier metal ion as compared to La
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Similar studies were also carried o
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3+ 3+ faster decay component is ass
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the other hand the Eu 3+ lifetime h
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3+ 4.4.8 Luminescence studies on Sm
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CHAPTER 5: Zinc gallate (ZnGa 2 O 4
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In pure EG an amorphous product is
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water content in the reaction mediu
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nucleation, thereby leading to incr
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particles. Thus the TEM studies als
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value. The lattice parameters calcu
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Quantum yield of the blue emission
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5.5.2. Eu 3+ doped ZnGa 1.5 In 0.5
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CHAPTER 6: Tungstates [MWO 4 (M = C
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ionic radius of the metal cation ca
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lattice. Asymmetric ratio is ~ 12 f
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700 Intensity (arb.units) 600 λ ex
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Intensity (arb.units) 25000 20000 1
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Strong green emission has been obse
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consists of strong band at 255 nm a
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peak can be attributed to the cryst
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nm) is observed from Er 3+ doped Ga
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and Dy 3+ doped CaWO 4 nanoparticle
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REFERENCES 1. D. J. Barber, I. C. F
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32. K. A. Gschneidner, Jr., L. Eyri
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65. Z. Deng, F. Tang, D. Chen, X. M
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100. A. Rouanel, J. J. Serra, K. Al
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130. F. Li, W. Jianhuai, L. Jiongti
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166. L. Fu, Z. Liu, Y. Liu, B. Han,
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205. R. Sasikala, V. Sudarsan, C. S
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238. E. Oldfield, R. A. Kinsey, K.
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271. B. G. Hyde, S. Andersson, ”I
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B. S. Naidu, B. Vishwanadh, V. Suda
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9. Room temperature synthesis of mu
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CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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