certificate -...

i

Dr. C.M. PADMA, M.Sc.,M.Phil.,Ph.D.

(Supervisor)

Associate Professor and HOD of Physics

Women's Christian College

Nagercoil - 629 001

Tamilnadu, India

and

Dr. C.K. MAHADEVAN, M.Sc.,Ph.D.,D.Sc.,M.N.A.Sc. (Co-Supervisor)

Associate Professor of Physics (Retired)

S.T.Hindu College

Nagercoil – 629 002

Tamilnadu, India

CERTIFICATE

This thesis entitled “STUDIES ON II-VI COMPOUND ADDED ADP

SINGLE CRYSTALS” submitted by J.ANITHA HUDSON for the award of

Degree of Doctor of Philosophy in Physics of Manonmaniam Sundaranar

University is a record of bonafide research work done by her and it has not been

submitted for the award of any degree, diploma, associateship, fellowship of any

University / Institution.

Place : Nagercoil

Date : June 20, 2014

Signature of Co-Supervisor Signature of Supervisor

ii

J. ANITHA HUDSON, M.Sc., M.Phil., B.Ed.

Physics Research Centre


Nagercoil - 629 001

Tamilnadu, India

DECLARATION

I hereby declare that the thesis entitled “STUDIES ON II-VI

COMPOUND ADDED ADP SINGLE CRYSTALS” submitted by me for the

Degree of Doctor of Philosophy in Physics is the result of my original and

independent research work carried out under the Guidance of Dr. C.M. PADMA,

Head of the Department of Physics, Women's Christian College,

Nagercoil - 629 001 and Co-guidance of Dr. C.K. MAHADEVAN, Associate

Professor of Physics (Retired), S.T.Hindu College, Nagercoil - 629002 and it has

not been submitted for the award of any degree, diploma, associateship, fellowship

of any University or Institution.

Place : Nagercoil

Date : June 20, 2014 J. ANITHA HUDSON

iii

ACKNOWLEDGEMENT

First and foremost, I raise my heart in profound gratitude to God Almighty

for his love and grace all through my life and especially during the course of this

research study.

I express my deep sense of gratitute to my guide, Dr. C.M. Padma (Head

of the Department of Physics, Women's Christian College, Nagercoil) for her

goodwill to be friendly, motivating, supporting, encouraging and guiding me at

every stage of my work and also I appreciate her generous willingness for the

successful completion of my research work. I am equally indebted to

Dr. C.K. Mahadevan, (Associate Professor of Physics (Retired), S.T.Hindu

College, Nagercoil) who spent much of his valuable time to sharpen my ideas that

enabled me to undertake this research work with courage and confidence .

I record my thanks to the Management of Women's Christian College for

extending the facilities to my research work. I am grateful to

Dr. Nirmala Nallathamby, the Principal of Women's Christian College, Nagercoil

for her encouragement and help.

I am greatly indebted to Dr. J. Daisy Magdaline, Department of Physics,

Rani Anna College, Tirunelveli for her timely help and suggestions. I would like

to extend my heartfelt thanks to the faculty members in the Physics Department of

Women's Christian College and S.T.Hindu College for their kind support and co-

operation during my research work. My special thanks to Dr. K.U. Madhu,

Dr. M. Meena and Dr. G. Jenita Christobel.

iv

I would like to extend my heartfelt thanks to my friends, fellow researchers

and former full time Ph.D Scholars Mrs. O.V. Mary Sheeja, Dr. S. Nagaveena,

Dr. C. Latha, Mrs. S.I. Srikrishna Ramya, Dr. R. Sunitha, Dr. I.S. Prameela

Kumari, Dr. D. Shiney Manoj, Dr. G. Deepa, Dr. K. Usha for their kind

encouragement and support.

I acknowledge the love, concern and moral support rendered by my

husband Mr. Y. Kevin Isaad, my affectionate children K. Ana Jessica and

K.Aaron Joshua, my beloved parents and in-laws during the tenure of my

research work.

My special thanks to Miss.Malar, Print Land, Nagercoil for her sincere

efforts in drafting of my thesis.

Finally, I extend my gratefullness to all those who have helped me directly

or indirectly in various ways throughout my research work.

J. ANITHA HUDSON

v

ABSTRACT

Name of the Candidate : J.ANITHA HUDSON

Research Centre and : Physics Research Centre,

Institution Women's Christian College,

Nagercoil – 629 001,

Tamil Nadu, India.

Submitted to : Manonmaniam Sundaranar University,

Tirunelveli – 627 012.

Field of study : Solid State Physics - Crystal Growth and

Characterization

Subject : PHYSICS

Guided : Dr. C.M. PADMA

Head of the Department of Physics


Nagercoil - 629 001

Co-Guided : Dr. C.K. MAHADEVAN

Associate Professor of Physics (Retired)

S.T. Hindu College

Nagercoil - 629 002

Title of the Thesis : STUDIES ON II-VI COMPOUND ADDED

ADP SINGLE CRYSTALS

No. of pages : xxiii + 218 + 20 (paper copies)

Key words : Ammonium dihydrogen phosphate; Slow

evaporation solution growth technique; II-VI

Compounds; Cadmium sulphide; Zinc

sulphide; Single crystals; X-ray diffraction;

FTIR; AAS; UV-Vis-NIR; Microhardness;

SHG; TG/DTA; Dielectric constant;

Dielectric loss; AC and DC electrical

conductivities.

vi

Most of the extraordinary achievements in modern technology have been

accomplished through the development of microelectronic, optoelectronic and

optical devices made of artificial crystals. The emergence of new high quality

single crystals remains a challenging endeavour of material science. Hence, the

discovery, growth and characterisation of novel materials and their design

especially in single crystal form is an urgent need.

Ammonium dihydrogen phosphate (ADP) is a commercially available

material with numerous laser based applications. ADP crystals exhibit excellent

dielectric, piezoelectric, electro-optic, nonlinear optical and antiferroelectric

properties. ADP crystals are commonly used in frequency conversion applications

such as second, third and fourth harmonic generation and in electro-optic

modulation. Easy growth of large single crystals, a broad transparency range and

relatively low production cost are the qualities that make this crystal attractive and

well suited to a variety of applications.

Dopants play an important role in improving the properties of a crystal.

Now a days the synthesis and properties of highly luminescent II-VI compound

semiconductor nanoparticles cadmium sulphide and zinc sulphide have been

extensively investigated from the basic research point of view to the application

field. But generally II-VI compounds including CdS and ZnS do not dissolve in

water. Now, the challenging problem is to find a way to dissolve II-VI compounds

CdS and ZnS and use them as dopants. Literature review also reveals that II-VI

compounds as additives have improved material properties.

vii

Therefore, with an aim of improving the quality of ADP crystals with better

nonlinear optical properties for both academic use and industrial applications, pure

and II-VI compounds (CdS and ZnS nanoparticles) doped ADP single crystals

were grown by using the slow evaporation solution growth technique at room

temperature. The dopants (CdS and ZnS) used in the present study were

synthesised by a simple microwave assisted solvothermal method. Ethylene

diamine was used as a capping agent to enhance their solubility in water. The

solubility of CdS and ZnS nanoparticles were found by the gravitational method.

A total of eleven crystals were grown and characterized.

The identity test of the crystal starts with X-ray diffraction studies, powder

X-ray diffraction studies were carried out to characterize the grown crystals

structurally. FTIR spectral analysis was carried out to identify the functional

groups of the grown crystals and band assignments were done for the crystals

grown in the present study. Atomic absorption spectral analysis was carried out

for the doped crystals to estimate the amount of metal ions present quantitatively.

The UV-Vis-NIR spectral study was carried out which reveals the wide

optical transmission window possessed by the grown crystals, an essential property

for NLO crystals. The initial testing of materials for second harmonic generation

was done with Kurtz-Perry powder technique to confirm the SHG efficiency of the

grown crystals. The crystals were also subjected to thermogravimetric (TG) and

differential thermal analysis (DTA) to understand their thermal stability.

DC and AC electrical measurements were carried out along both a- and c-

directions by the two probe-method and parallel plate capacitor method

viii

respectively. Measurements were carried out at various temperatures ranging from

40-150 0C. DC and AC activation energies were also determined.

Ethylene diamine capped CdS and ZnS nanoparticles show enhanced

solubility. Results show that there is a significant enhancement of SHG efficiency

and CdS and ZnS doping helped in tuning significantly the optical and electrical

properties of ADP crystal.

A report of this research work is presented in this thesis.

ix

LIST OF TABLES

TABLE

NO. TITLE

PAGE

NO.

1.1 Recent trends in crystal growth 65

3.1

The estimated average lattice parameters (the e.s.d.s are

given in parentheses) and metal atom contents in the doped

crystals

118

3.2 FTIR wavenumbers and their vibrational assignments for

Pure ADP, CADP-5 and ZADP-5 crystals 121

3.3

The estimated work hardening co-efficients (n), optical cutoff

wavelengths, optical transmission percentages and SHG

efficiencies (in ADP unit) for pure and doped ADP crystals

131

3.4 Dielectric constant values for pure and CdS doped ADP

crystals along 'a' direction 134

3.5 Dielectric constant values for pure and CdS doped ADP

crystals along 'c' direction 134

3.6 Dielectric constant values for pure and ZnS doped ADP


3.7 Dielectric constant values for pure and ZnS doped ADP


3.8 Dielectric loss factor values for pure and CdS doped ADP


3.9 Dielectric loss factor values for pure and CdS doped ADP


3.10 Dielectric loss factor values for pure and ZnS doped ADP


3.11 Dielectric loss factor values for pure and ZnS doped ADP


3.12 AC electrical conductivity values for pure and CdS doped

ADP crystals along 'a' direction 150

3.13 AC electrical conductivity values for pure and CdS doped

ADP crystals along 'c' direction 150

x

TABLE

NO. TITLE

PAGE

NO.

3.14 AC electrical conductivity values for pure and ZnS doped


3.15 AC electrical conductivity values for pure and ZnS doped


3.16 DC electrical conductivity values for pure and CdS doped


3.17 DC electrical conductivity values for pure and CdS doped


3.18 DC electrical conductivity values for pure and ZnS doped


3.19 DC electrical conductivity values for pure and ZnS doped


3.20 Activation energies estimated for pure and CdS doped ADP

crystals 163

3.21 Activation energies estimated for pure and ZnS doped ADP

crystals. 163

C-1 Indexed PXRD data for pure ADP 207

C-2 Indexed PXRD data for CADP-1 208





C-7 Indexed PXRD data for ZADP-1 213





xi

LIST OF FIGURES

Figure

No. Title

Page

No.

1.1 Classification of solid materials 5

1.2 Estimated shares of world crystal production in 1999 5

1.3 Inter-disciplinary nature of crystal growth technology 12

1.4 Categories of crystal growth techniques 12

1.5 Solubility diagram showing different levels of saturation 24

1.6 Schematic diagram of the apparatus for the slow cooling

method 28

1.7 Schematic diagram of the apparatus for the temperature

gradient method 28

1.8 Experimental set up for the SR method 30

1.9 Schematic diagram of a simple apparatus for the slow (free)

evaporation method 30

1.10 The external morphology of ADP single crystal 36

1.11 The (100) projection of ADP structure 36

1.12 The picture of ADP molecule 38

1.13 The unit cell structure of ADP crystal 38

1.14 The bond graph of ADP 38

2.1 Photographs of the as-prepared CdS nanoparticles: (a) with

capping and (b) without capping 76

2.2 Photographs of the as-prepared ZnS nanoparticles: (a) with

capping and (b) without capping 76

2.3 Powder sample diffracts X-ray beam in cones 83

xii

Figure

No. Title

Page

No.

2.4 The diffractometer beam path in θ/2θ mode 83

2.5 A photograph of the powder X-ray diffractometer 83

2.6 Schematic diagram of the atomic absorption process 89

2.7 The calibration graph between concentration and absorbance 89

2.8 Schematic diagram of FTIR spectrometer 89

2.9 Schematic diagram of Vicker's pyramid indendation mark 97

2.10 Schematic diagram of resistance to motion of dislocations 97

2.11 Vicker's hardness tester 97

2.12 Energy level diagram with electronic transitions 107

2.13 Photograph of an experimental set up for UV-Vis-NIR

spectral recording 107

2.14 Schematic experimental set up for SHG efficiency

measurement 107

2.15 Photograph of an LCR meter 111

2.16 Photograph of a million megohm meter 111

3.1 Photograph of the pure and CdS doped ADP single crystals 115

3.2 Photograph of the pure and ZnS doped ADP single crystals 115

3.3 Indexed PXRD patterns of pure and CdS doped ADP crystals 117

3.4 Indexed PXRD patterns of pure and ZnS doped ADP crystals 117

3.5 FTIR spectra observed for Pure ADP, CADP-5 and ZADP-5

crystals 121

3.6 Variation of Vicker's hardness number with load for pure and

CdS doped ADP crystals 124

xiii

Figure

No. Title

Page

No.

3.7 Variation of Vicker's hardness number with load for pure and

ZnS doped ADP crystals 124

3.8 Plots of log P vs log d for Pure and CdS doped ADP crystals 125

3.9 Plots of log P vs log d for Pure and ZnS doped ADP crystals 125

3.10 TGA and DTA thermograms of Pure ADP crystal 128

3.11 TGA and DTA thermograms of CADP-5 crystal 128

3.12 TGA and DTA thermograms of ZADP-5 crystal 128

3.13 UV-Vis-NIR transmission spectra for pure and CdS doped

ADP crystals 130

3.14 UV-Vis-NIR transmission spectra for pure and ZnS doped

ADP crystals 130

3.15 Variation of dielectric constant with temperature for pure and

CdS doped ADP crystals along 'a' direction 136


CdS doped ADP crystals along 'c' direction 136


ZnS doped ADP crystals along 'a' direction 137


ZnS doped ADP crystals along 'c' direction 137

3.19

Plots showing impurity concentration dependence of dielectric

constant for pure and CdS added ADP crystals along 'a'

direction

138

3.20


constant for pure and CdS added ADP crystals along 'c'

direction

138

3.21


constant for pure and ZnS added ADP crystals along 'a'

direction

139

xiv

Figure

No. Title

Page

No.

3.22


constant for pure and ZnS added ADP crystals along 'c'

direction

139

3.23 Variation of dielectric loss with temperature for pure and CdS

doped ADP crystals along 'a' direction 143

3.24 Variation of dielectric loss with temperature for pure and CdS

doped ADP crystals along 'c' direction 143

3.25 Variation of dielectric loss with temperature for pure and ZnS

doped ADP crystals along 'a' direction 144

3.26 Variation of dielectric loss with temperature for pure and ZnS

doped ADP crystals along 'c' direction 144

3.27 Plots showing impurity concentration dependence of dielectric

loss for pure and CdS added ADP crystals along 'a' direction 145


loss for pure and CdS added ADP crystals along 'c' direction 145


loss for pure and ZnS added ADP crystals along 'a' direction 146


loss for pure and ZnS added ADP crystals along 'c' direction 146

3.31 Variation of AC conductivity with temperature for pure and








3.35

Plots showing impurity concentration dependence of AC

conductivity for pure and CdS added ADP crystals along 'a'

direction

154

xv

Figure

No. Title

Page

No.

3.36


conductivity for pure and CdS added ADP crystals along 'c'

direction

154

3.37


conductivity for pure and ZnS added ADP crystals along 'a'

direction

155

3.38


conductivity for pure and ZnS added ADP crystals along 'c'

direction

155

3.39 Variation of DC conductivity with temperature for pure and








3.43

Plots showing impurity concentration dependence of DC

conductivity for pure and CdS added ADP crystals along 'a'

direction

160

3.44


conductivity for pure and CdS added ADP crystals along 'c'

direction

160

3.45


conductivity for pure and ZnS added ADP crystals along 'a'

direction

161

3.46


conductivity for pure and ZnS added ADP crystals along 'c'

direction

161

3.47 Plots of log σac versus 1000/T (K

-1) for Pure ADP crystal:

(a) along 'a' direction and (b) along 'c' direction 164

xvi

Figure

No. Title

Page

No.


-1) for CADP-1 crystal:















-1) for ZADP-1 crystal :






-1) for ZADP-3 crystal:



-1) for ZADP-4 crystal:





3.58 Plots of log σdc versus 1000/T (K

-1) for Pure ADP crystal:






-1) for CADP-2 crystal :





xvii

Figure

No. Title

Page

No.






















xviii

CONTENTS

CHAPTER

NO. TITLE

PAGE

NO.

1. INTRODUCTION 1

1.1 Crystalline State 1

1.2 Natural and Artificial (Synthetic) Crystals 3

1.3 Crystal Growth and Its Importance 4

1.4 Significance of Single Crystals 6

1.5 Crystal Growth Technology 8

1.6 Methods of Crystal Growth 10

1.6.1 Growth from solid 11

1.6.2 Growth from vapour 13

1.6.3 Growth from liquid 13

1.7 Growth from Melt 14

1.7.1 Czochralski technique 14

1.7.2 Bridgeman – Stockbarger technique 15

1.7.3 Vernueil technique 15

1.7.4 Zone melting technique 16

1.7.5 Skull melting process 16

1.7.6 Shaped crystal growth technique 17

1.8 High Temperature Solution Growth (Flux Growth) 17

1.9 Hydrothermal Growth 18

1.10 Low Temperature Solution Growth 19

1.10.1 Criteria for growth 19

1.10.2 Metastable zone width 19

xix

CHAPTER

NO. TITLE

PAGE

NO.

1.10.3 Crystal-medium interface 20

1.10.4 Solvents 20

1.10.5 Impurities 21

1.10.6 Stirring 22

1.10.7 Growth temperature 22

1.10.8 Solubility and supersaturation 23

1.11 Classification of Low Temperature Solution Growth

Methods

25

1.11.1 Slow cooling method 25

1.11.2 Temperature gradient method 26

1.11.3 Gel method 26

1.11.4 SR method 27

1.11.5 Slow evaporation method 29

1.12 Nonlinear Optics and Crystalline Materials 31

1.13 ADP Single Crystals 34

1.14 Structure of ADP 35

1.15 Review of Studies on ADP Single Crystals 40

1.15.1 Growth techniques 40

1.15.2 Growth rate, structural properties and

phase transition

43

1.15.3 Electrical properties 55

1.15.4 Optical properties 57

1.15.5 Mechanical properties 60

1.16 Recent Developments in the Field of Crystal Growth 60

1.17 Present Work 66

xx

CHAPTER

NO. TITLE

PAGE

NO.

2. MATERIALS AND CHARACTERIZATION

TECHNIQUES

70

2.1 Materials Used 71

2.2 Preparation of II-VI Compound Nanoparticles

(Dopants)

72

2.2.1 Importance of II-VI compound nanoparticles 72

2.2.2 Applications of CdS and ZnS nanoparticles 73

2.2.3 Challenging problem 73

2.2.4 Synthesis of water soluble ethylene diamine

capped CdS and ZnS nanoparticles

75

2.2.5 Visible colour change 77

2.2.6 Solubility of as-prepared CdS and ZnS

nanoparticles

78

2.3 Growth of Sample Crystals 78

2.4 Characterization Techniques 80

2.5 X-ray Diffraction Technique 81

2.5.1 Powder X-ray diffraction analysis 82

2.5.2 Powder X-ray diffraction instrumentation 84

2.6 Atomic Absorption Spectroscopy 85

2.7 Fourier Transform Infrared (FTIR) Spectroscopic

Technique

88

2.8 Microhardness Measurement 93

2.8.1 Factors obstructing the motion of dislocations 96

2.8.2 Vicker's hardness test 98

2.9 Thermal Studies 99

2.9.1 Differential thermal analysis 101

xxi

CHAPTER

NO. TITLE

PAGE

NO.

2.9.2 Thermogravimetry 102

2.10 Ultraviolet-Visible-Near Infrared (UV-Vis-NIR)

Spectroscopic Technique

103

2.11 Second Harmonic Generation Test 105

2.12 Electrical Measurements 108

2.12.1 AC electrical (dielectric) measurements 108

2.12.2 DC conductivity measurements 112

3. RESULTS AND DISCUSSION 114

3.1 General Properties 114

3.2 Lattice Variation and Impurity Concentration 116

3.3 AAS Data 119

3.4 FTIR Spectra 120

3.5 Mechanical Properties 122

3.6 Thermal Properties 126

3.7 Optical Properties 127

3.7.1 UV-Vis-NIR spectra 127

3.7.2 SHG efficiencies 129

3.8 Electrical Properties 132

3.8.1 Dielectric constants 132

3.8.2 Dielectric losses 140

3.8.3 AC electrical conductivities 147

3.8.4 DC electrical conductivities 148

3.8.5 Activation energies 162

4. SUMMARY AND CONCLUSIONS 172

xxii

CHAPTER

NO. TITLE

PAGE

NO.

5. SUGGESTION FOR FUTURE WORK 178

REFERENCES 179

APPENDIXES 203

A. Resume of the Candidate 203

B. Publications Made By the Candidate 204

C. Indexed PXRD Intensity Data 207

D. Published Papers 218

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