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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