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TITLE
DEDICATION
CERTIFICATE
DECLARATION
ACKNOWLEDGEMENT
CONTENTS
Preface
1. CRYSTAL GROWTH: THEORY AND TECHNIQUES
1.1 Introduction
1.2 The Thermodynamics of Crystal Growth
1.3 Nucleation
Fig. I. 1 Free energy change of nucleus as a function of radius
1.4 Crystal Growth Theories
1.4.1 Surface energy theory
1.4.2 Diffusion theory
1.4.3 Surface nucleation model
Fig. 1.2 Possible lcttice sites for the attachment of absorbed atom
1.4.4 Screw dislocation theory
Fig. 1.3 Development of a spiral
1.5 Crystal Growth Techniques
1.5.1 Solid growth techniques
1.5.2 Growth from vapour
Physical vapour transport (PVT) )
Chemical vapour transport
1.5.3 Melt growth technique
1.5.4 Growth from solution
High temperature solution growrh
Hydrothermal methods
Low temperature solution growth
The gel method
References
2. RARE EARTH OXALATE CRYSTALS AND GEL TECHNIQUES
2.1 Introduction
2.2 History of Gel Method
2.3 Preparation of Hydrosilica Gel
2.4 The Mechanism of Gelation and the Structure of Gel
2.5 Advantages of Gel Medium
2.6 Crystallization in the Gel Medium
2.6.1 The chemical reaction method
2.6.2 Chemical reduction method
2.6.3 Solubility reduction method
2.6.4 Complex dilution method
Fig.2. 1 Crystallization by chemical reaction method.
2.7 Nucleation Control Methods
References
3. EXPERIMENTAL TECHNIQUES IN CHARACTERIZATION
3.1 Introduction
3.2 Optical Microscopy
3.3 Atomic Force Microscopy
Fig.3.1 Nanoscope 1 1 1 Block Diagram with AFM.
3.4 Micro Hardness Studies
3.5 X-ray Diffraction Methods
3.6 Infrared Spectroscopy
3.7 UV-Visible-Near Infrared Spectroscopy
3.8 Thermal Analysis
3.9 Electron Spectroscopy for Chemical Analysis
3.10 Energy Dispersive Analysis by X-rays (EDAX)
3.11 Vibrating Sample Magnetometer
References
4. THE GROWTH PROCESS
4.1 Introduction
4.2 The Chemistry of Reactions
4.3 Hydrosilica Gel as the Medium of Growth
4.4 Preparation of the Gel
Fig.4.1 Specific gravity of SMS solution Vs partial volume of water.
Fig. 4.2 Gelation period vs. pH of the medium
4.5 Preparation of the Supernatant Solution
4.6 Growth of Praseodymium Samarium Oxalate (PSO) Crystals
4.7 Growth of Neodymium Praseodymium Oxalate (NPO) Crystals
Fig.4.3 Growth system of NPO crystals under different stoichiometry
Fig.4.4 Growth system of NSO crystals under different stoichiometry
4.8 Growth of Neodymium Samarium Oxalate (NSO) Crystals
4.9 The Growth Kinetics
Fig. 4.5 Nucleation density for different gel density
4.9.1 Effect of gel density
Fig. 4.6 Variation of nucleation density with pH of the gel
4.9.2 Effect of pH of the gel
Fig. 4.7 Variation of nucleation density with age of the gel
4.9.3 Effect of ageing of the get
Fig. 4.8 Variation of nucleation density with concentration of the feed solution
4.9.4 Effect of concentration of the reactants
Fig. 4.9 Variation of nucleation density with acidityin feed solution
4.9.5 Effect of acidity of the feed solution
Fig. 4.10 Movement of crystalization zone withacid content in the feed solution
Fig.4.11 Growth system of PSO crystals with different acid concentration in the feed solution
Fig.4.12 Growth system of PSO crystal under concentration
4.9.6 Concentration programming
CONCLUSION
References
5. MICROTOPOGRAPHICAL STUDIES
5.1 Introduction
5.2 Morphology of the Crystals
5.3 Microscopic Studies
Fig.5.1 (100) face of PSO crystal with thin growth layer
Fig.5.2 (100) face of PSO crystal with thick growth layer (x 50)
Fig 5.3 Interaction of a thick growth layer on (100) face (x 200)
Fig.5.4 Mottled nature of (100) face
Fig 5.5. Crystallise aggregates in (100) face (x 200)
Fig.5.6 Impression of a detached foreign crystal (x100)
5.4 Micro topography by AFM
Fig.5.7 AFM photograph showing nanolayers and crack of NPO crystal
Fig 5.8 AFM photograph of a large crack on the surface of NPO crystal
Fig 5.9. AFM photograph of parallel cracks on the surface of NPO crystal
Fig.5.10 AFM photograph spreading layers on the surface of NPO crystal
Fig 5.11 AFM photograph showing hillocks on the surface of PSO crystal
Fig.5.12 AFM photograph showing cluster of hillocks on the surface of PSO crystal
5.5 Etching Studies
5.5.1 Formation of dislocation etch pits
5.5.2 Dislocation study of the crystals
5.5.3 Cleavage surfaces
5.5.4 Selection of the etchant
5.5.5 Etch pits on (100) face
Fig 5.13 Cleaved matched face of PSO crystal (x 50)
Fig 5.14 General nature of etch pits on (100) face (x 200)
Fig.5.15 (100) face etched for 20 seconds (x 50)
Fig.5.16 Continuous etching of (100) face for 40 seconds (x 50)
Fig.5.17. Continuous etching of (100) face for 60 seconds (x 50)
5.5.6 Etching of (110) face
5.5.7 Etching of cleaved surface
Fig.5.18 (110) face etched for 20 seconds (x 200)
Fig.5.19 Continuous etching of (110) face for 40 seconds (x 200)
Fig.5.20 Continuous etching of (110) face for 60 seconds (x 200)
Fig 5.21 Eccentric etch pits on (110) face (x 200)
Fig.5.22 Etch pits on a cleaved surface (x 100)
Fig.5.23 Etch pits on the cleaved matched surface (x 100)
5.5.8 Discussion on etching studies
5.6 Micro hardness Studies
5.6.1 Micro hardness studies of mixed rare earths oxalate Crystals
Fig. 5.24 Variation of microhardness with applied load
References
6. CHARACTERIZATION OF THE CRYSTALS
6.1 X-ray Analysis
6.1.1 Lattice parameters of PSO crystals
Fig.6.1 X-ray powder diffraction patterns of PSO crystals
Table 6. I. X-ray powder diffraction data for PrSrn (C2O4) 3 10 H20.
6.1.2 Lattice parameters of NPO crystals
Fig.6.2 X-ray powder diffraction patterns of NPO crystals
Table 6.2. X-ray powder diffraction data for NdPr (C204) 3 10 H20.
6.1.3 Lattice parameters of NSO crystals
Fig.6.3 X-ray powder diffraction piitterns of NSO crystals
Table 6.3. X-ray powder diffraction data for NdSm (C2O4) 3 10 H20.
Table 6.4. Comparative study of the lattice parameters of single and mixed rare earth oxalate crystals with La2 (c2o4) 3. 10H2O.
6.2 Infrared Absorption Studies
Table 6.5. Expected modes of vibration.
6.2.1 Water vibrations
6.2.2 Oxalate vibrations
6.2.3 Metal-oxygen vibrations
6.3 Thermal Analysis
63.1 Thermal analysis of PrSm (C2O4) 310H2O
6.3.2 Thermal analysis of NdPr (C2O4) 3 10H2O
6.3.3 Thermal analysis of NdSm (C2O4) 3. 10H2O
6.4 XPS Studies
6.4.1 XPS of PSO
6.4.2 XPS of NPO
6.4.3 XPS of NSO
6.5 Energy Dispersive X-ray Analysis (EDAX)
6.5.1 EDAX of PSO
6.5.2 EDAX of NSO
6.5.3 EDAX of NPO
6.6 Magnetic Susceptibility Measurements
References
7. LASER INTENSITY PARAMETERS OF NdPr (C2O4) 3.I0H2O
7.1 Introduction
7.2 The Rare Earth Ions
7.3 Optical Absorption Studies
7.4 Oscillator Strength
Fig.7.1 Visible absorption spectrum of NPO crystals
Fig.7.2 NIR absorption specma of NPO crystals
Tabel 7.1 Energy values and oscillator strengths of Nd3+ ions in the crystal.
Table 7.2 Energy values and oscillator strengths of pr3+ ions in the crystal.
7.5 Spectroscopic Parameters
7.6 Judd-Ofelt Model
Table 7.3 Calculated spectral parameters of Nd3+ and pr3+ ions in the crystal.
7.7 Radiative Properties
7.8 Results and Discussion
Table 7.4 Calculated values of Sed, Smd A, AT, ҐR, βR and σa for Nd3+ ion in the crystal.
7.8.1 Radiative properties of Nd3+ ion in NPO
7.8.2 Radiative properties of Pr3+ ion
7.9 Conclusions
References
8. GENERAL CONCLUSION