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TITLE
DEDICATION
CERTIFICATE
DECLARATION
ACKNOWLEDGEMENT
CONTENTS
PREFACE
1. THEORIES AND TECHNIQUES OF CRYSTAL GROWTH
1.1 Introduction
1.2 The thermodynamics of crystal growth
1.3 Nucleation
1.4 Theories of crystal growth
1.4.1 Surface energy theory
1.4.2 Diffusion theories
1.4.3 Surface nucleation model
1.4.4 Screw dislocation theory
1.5 Crystal growth techniques
1.5.1 Solid state growth techniques
1.5.2 Growth from solution
1.5.2 (i) High temperature solution growth
1.5.2 (ii) Hydrothermal growth
1.5.2 (iii) Low temperature solution growth
1.5.2 (iv) The gel method
1.5.3 Growth from vapour
1.5.3 (i) Physical vapour transport (PVT)
1.5.3 (ii) Chemical vapour transport (CVT)
1.5.4 Melt growth techniques
1.5.4.1 (a) Bridgemann method
1.5.4.1 (b) Czochralski method
1.5.4.2 Zone growth method
References
2. CRYSTAL GROWTH BY GEL TECHNIQUE
2.1 Introduction
2.2 Advantages of gel technique
2.3 The structure and properties of gel
2.4 Preparation of hydrosilica gel
2.5 The gelling mechanism
2.6 Crystallisation process in gel medium
2.6.1 The chemical reaction method
Fig. 2. I Crystallisation in single tubes by chemical reaction method
Fig. 2.2. Crystallisation by gel method employing U tube
2.6.2 The chemical reduction method
2.6.3 Complexion decomplexion method
2.6.4 Solubility reduction method
2.7 Growth mechanism in gel
2.8 Control of nucleation in gel growth
2.9 Habit of the gel grown crystals
References
3. EXPERIMENTAL TECHNIQUES FOR CHARACTERISATION AND PROPERTY STUDIES OF CRYSTALS
3.1 Introduction
3.2 Optical microscopy
3.3 Etching studies
3.4 X-ray diffraction methods
3.5 FT-IR spectroscopy
3.6 Thermal analysis
3.6.1 Thermogravimetric analysis (TGA)
3.6.2 Differential thermal analysis (DTA)
3.7 Absorption and emission spectrometry
3.7.1 UV-Visible absorption spectroscopy
3.7.2 Emission spectrometry
3.8 Energy dispersive analysis by X-rays (EDAX)
3.9 Microhardness measurements
3.10 Magnetic measurements (VSM)
References
4. GROWTH OF MONO AND MIXED RARE EARTH HYDROGEN SELENITE CRYSTALS
4.1 Introduction
4.2 Chemical reaction associated with growth
4.3 Hydrosilica gel as growth medium
4.3.1 Preparation of hydrosilica gel
4.4 Preparation of feed (supernatant) solution
4.5 Observed growth kinetics of rare earth hydrogen selenite crystals
4.5.1 Praseodymium hydrogen selenite
4.5.1 (i) Effect of the pH value
4.5.1 (ii) Influence of the gel density and ageing
4.5.1 (iii) Influence of the concentration of reactants Growth of mixed hydrogen selenite crystals
4.5.2 Growth of mixed hydrogen selenite crystals
4.5.2 (i) Praseodymium neodymium hydrogen selenite
4.5.2 (ii) The effect of pH
Fig.4.8 The crystalliser containing the mono (single) rare earth hydrogen selenite crystals
Fig.4.9 The crystalliser containing the mixwd rare earth hydrogen selenite crystals
4.5.2 (iii) Influence of age and gel density
4.5.2 (iv) Effect of concentration of feed solution
4.5.3General features observed on the growth of mixed rare earth hydrogen selenite crystals
4.6 Conclusion
References
5. CHARACTERISATION OF THE GROWN CRYSTALS
5.1 Introduction
5.2 Surface study of crystals
5.2.1 Morphology of the rare earth hydrogen selenite crystals
Fig. 5.1 Morphology of rare earth hydrogen selenite crystals
Fig. captions
Fig.5.2 Different morphologies and etch pattern of grown crystals
5.3 Spectroscopic analysis
5.3.1 X-ray analysis
5.3.2 Infrared spectra of crystals
5.3.3 UV-Visible absorption and emission spectra of rare earth hydrogen selenites
Fig. 5.9 The experimental set-up for emission spectral studies
5.4 Energy dispersive X-ray analysis (EDAX)
5.4.1 EDAX of praseodymium neodymium hydrogen selenite
5.4.2 EDAX of praseodymium samarium hydrogen selenite
5.4.3 EDAX of neodymium samarium hydrogen selenite
5.5 Thermal analysis
5.5.1 Thermogravimetric analysis (TGA)
5.5.2 The differential analysis (DTA)
5.6 Conclusion
References
6. MICROHARDNESS STUDIES OF GROWN CRYSTALS
6.1 Introduction
6.2 Vickers test
Fig. 6.1. Vickers pyramid having square shaped base and depth of indentationcorresponds to: l/71h of the indentation diagonal
6.3 Corrections in measurements
6.4 Microindentation studies at low loads
6.5 Results and discussion
6.5.1 Variation of hardness with load
6.5.2 Influence of rare earth on the hardness of mixed crystals
6.6 Conclusion
References
7. MAGNETIC PROPERTIES OF RARE EARTH HYDROGEN SELENITE CRYSTALS
7.1 Introduction
7.2 Theories of atomic paramagnetism
7.3 Paramagnetism
Table 7.1 Diamagnetic susceptibility per gram ion of the elements and groups used for crystallisation.
7.4 Magnetic properties of rare earth ions
7.5 Magnetic measurements
7.5.1 Stationary coil method
7.5.2 Moving-coil (extraction) method
7.5.3 Rotating-coil method
7.5.4 Vibrating coil magnetometer
7.5.5 Vibrating sample magnetometer (VSM)
Fig. 7.3 The schematic diagram of VSM
7.6 Results and discussion
7.7 Conclusion
References
8. GENERAL CONCLUSION
8.1 Introduction
8.2 Conclusions
8.3 Scope for future research
References