chapter 3 experimental techniquesshodhganga.inflibnet.ac.in/bitstream/10603/7346/9/09_chapter...

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CHAPTER 3

EXPERIMENTAL TECHNIQUES

3.1 INTRODUCTION

Crystals grown by different methods have different applications. To find the utility of such grown crystals, they have to be characterized and evaluated for their properties and behaviour. The determination of physico-chemical, thermal, mechanical, optical, electrical, and opto-electronic properties of a material is referred to as ‘Characterization’. The necessary input for the characterization and the analysis of grown crystals is the adequate understanding of experimental methods and the instrumentation involved. The observations needed during the present investigation have been recorded employing different experimental techniques such as x-ray diffraction, energy dispersive analysis of x-rays, thermal analysis, measurements of magnetic susceptibility and micromechanical properties, resistivity, thermoelectric power, FTIR, UV-VIS-NIR spectroscopy. These techniques with experimental details and the apparatus required are succinctly outlined in this chapter. 3.2 X-RAY TECHNIQUES

Various x-ray techniques and methods are available for the analysis of materials which can be classified into three main categories, viz. x-ray absorption, x-ray fluorescence and x-ray diffraction. We are concerned here with the diffraction of x-rays to reveal atomic level structure. 3.2.1 X-RAY POWDER DIFFRACTION

X–ray diffraction is an important technique that has long been used to address all issues related to the crystal structure, including lattice constants and geometry, identification of unknown materials, orientation of polycrystals, defects and stresses etc1,2). In the present study, powder diffractometer consisting of a Cu target x-ray tube of 2 KV, 3373/00 Cu LEF was utilized for obtaining diffractograms. The diffracted radiation is detected by PW3001 (Miniprop.) detector which moves through an adjustable range of reflections. The essential features of a diffractometer are shown schematically in Fig. 3.1. Data collection with the diffractometer, in general, requires approximately 100 times of the substance than the conventional Debye-scherrer method. Compared with other photographic methods, the diffractometry, in most cases, offers essential advantages due to its higher sensitivity, the higher resolving power, the accuracy of the intensity measurements and the elimination of elaborate

Ch.3.Experimental technique

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work in dark room. Above all, the diffractometric records can be obtained in a much shorter time as well as more conveniently than with photographic methods and hence powder diffractometry was employed in the present investigation.

A diffractometer is designed somewhat like a Debye Scherrer camera, except

that a movable counter replaces the strip of film. In both the instruments, essentially monochromatic radiation is used and the x-ray detector placed on the circumference of a centered on the powder specimen. For obtaining the diffractogram from a powdered sample, the counter is set near 2θ = 0o and then connected to a counting-rate meter. The output of this circuit is fed to a strip-chart recorder. The counter is then driven at a constant angular velocity through increasing values of 2θ until the whole angular range is scanned. At the same time, the paper chart on the recorder moves at a constant speed so that the distances along the length of the chart are proportional to 2θ. This results in a diffractogram showing a record of counts per second (proportional to diffracted intensity) versus diffraction angle 2θ. Only those (h k l) planes which are parallel to the mount plane contributed to the diffracted intensity. 3.2.2 ENERGY DISPERSIVE ANALYSIS OF X-RAY “The Energy Dispersive Analysis of X-rays” is an inevitable tool to estimate the semiquantitative chemical composition of crystals. The EDAX spectrum gives information about the chemical elements present in the sample, irrespective of their state of chemical combination of phases in which they exist, unlike the x-ray diffraction which discloses various compounds and phases present in the sample. Hence the EDAX is a much more rapid method of chemical analysis and is non-destructive. The quantitative detection limit for homogeneously distributed element is often 0.1 – 0.01 atomic percentage. In the present investigation ‘Philips’ EM400 scanning electron microscope with an EDS attachment is used for the purpose of an elemental analysis by energy dispersion method. The EDS system is capable of identifying elements with atomic number Z≥ 4 in a few minutes, the details of which are described by Goldstein and Yokowitz3). The principle underlying EDAX is the same as that of electron probe analysis. When a beam of electrons strikes a specimen, a fraction of the incident electrons would excite the atoms of the specimen, and emission of x-rays occurs while they return to their ground states. The energies of these x-rays are strictly dependent upon the atomic number of the elements excited and their detection forms the basis of the elemental analysis in the electron microscope. The EDS detector collects the x-ray spectrum emitted by the sample and the peaks are separated on the basis of their


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energies by means of Si (Li) counter and multichannel analyzer (MCA); this counter produces pulses proportional in height to the energies in the incident beam, and then the MCA sorts out various pulse heights. Moseley’s law relates the characteristic energy of the x-ray peak and the atomic number of the element responsible for the peak. Hence, by determining the channel numbers (energy) of peaks in the spectrum, appropriate atomic numbers can be assigned for the elements present in the electron-irradiated region. Since there is no physical separation in space of the various wavelengths (energies) such a spectrometer is often called non-dispersive. 3.3 THERMAL ANALYSIS Thermal analysis is the measurement of a property of a crystalline sample as a function of temperature while the substance is subjected to a controlled temperature program. The thermal methods4) of investigation are generally referred to as thermoanalytical techniques. Modules available to perform are: TGA, DTA, DSC, TMA, DMA etc. 3.3.1 THERMOGRAVIMETRIC ANALYSIS (TGA) Thermogravimetry is a technique which records the weight of a substance in an environment heated or cooled at a control rate as a function of time or temperature. The measurements carried out in the presence of change environment, whether it is inert or oxidative, reflects the useful information of the sample. The TGA instrument ‘Perkin Elmer’, Model: TGA-7 (Fig. 3.2) is based on a rugged microbalance which is highly sensitive and allows the sensitive measurement of weight changes as small as few micrograms. It can employ a temperature range from room temperature to 1000 oC. It provides the analysis with a quantitative measurement of any weight changes associated with a transition on varying temperature. It can directly record the mass loss, if any, with temperature due to dehydration or decomposition. The sample under the experiment was packed uniformly in the molybdenum boat to be placed in the furnace of the TG analyzer, and the boat is attached to an automatic recording balance. The change in weight is simultaneously recorded with time when the temperature is increased at a known uniform rate. This permits recording the loss in weight as a function of both time and temperature. The heating is carried out until there is no further loss in weight. Thermograms obtained are characteristic of the unique sequence of physico-chemical changes which may occur over definite temperature ranges. 3.3.2 DIFFERENTIAL THERMAL ANALYSIS (DTA)


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The ‘Perkin Elmer’, Model: DTA-7 system shown in Fig 3.3 is used for

differential thermal analysis. The DTA makes direct quantitative measurement of endothermic and exothermic behavior of host sample material at temperatures ranging from ambient temperature to 1600 οC. The instrument measures temperature difference ∆T between sample and a reference material. Simultaneous operation with other thermal analyzers as TGA-7, DMA-7 & TMA-7 is possible. During the analysis, if a transition occurs in the sample, thermal energy is added or subtracted from the sample and the reference material at the same temperature. Since this energy input is precisely equivalent in magnitude to the energy absorbed or evolved with the particular transition, a recording of this balancing yields a direct calorimetric measurements of the transition energy. This energy difference is manifested as enthalpic change – either exothermic or endothermic. The DTA curve would be parallel to the temperature axis till the sample undergoes any physical or chemical change of state. However, as soon as the sample has reached the temperature of the change of state, the additional heat flux reaching the sample will not increase the sample temperature at the same rate as that of the reference, and the differential signal appears as a peak. The differential signal would return to the base line only after the change of state of the sample is completed and the temperature becomes equal to that of the reference material. 3.3.3 DIFFERENTIAL SCANNING CALORIMETRY (DSC)

The Differential Scanning Calorimetery (DSC) is the fundamental technology to study and analyse the properties such as melting, glass transition, thermal history, crystallization, curing point, reaction kinetics, oxidative stability. It is also used to find specific heat, purity, polymorphism, chemical reaction measurements. The DSC instrument ‘Perkin Elmer’, Model: Pyris-1 DSC (Fig. 3.4) is based on power compensation method which allows sensitive measurement of even microgram weight changes, in the temperature range from room temperature to 1500 °C having the rate of cooling as 2 to 110 °C/min. Its calorimetric sensitivity is 1µW. When an exothermic or endothermic change occurs in the sample material, power (energy) is applied or removed from the calorimeter. This amount of power involved is directly proportional to the energy change which is recorded. It is a unique method in the sense that it makes use of constantan disc as the primary means of heat transfer to the sample and reference positions. The cell temperature is controlled by using a silver heating block, a resistance wound heater and a closely coupled Platinel II control thermocouple. The block temperature is monitored by control thermocouple and an appropriate amount of power is supplied to the heater as determined by the difference


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signal between control thermocouple and the output of programmer. Heat from the block then flows radially through the constantan disc towards the sample and reference platforms. Temperatures at the raised sample and reference platform are monitored by Chromel-Constantan thermocouple. The difference signal between the two thermocouple junctions is fed to the amplifier and monitored on the Y-axis of the X-Y recorder. Variances in the sample property, energy absorption or release, weight or dimensional change etc. are read on the Y axis as a function of sample temperature on the X-axis of the recorder. 3.4 MEAREMENTS OF ELECTRICAL PARAMETERS 3.4.1 ELECTRICAL RESISTANCE

A portable dc instrument ‘MEGGER’, Megohmmeter MM29 from THORN EMI Instruments, UK, is used for the direct measurement of dc resistance of resistive elements and insulation resistance of non-conductors at stress voltages upto 1000V d.c. The instrument is powered by internal supply of 9V which provides (constant current) power only during measurement process. The assembly of the measurement set up is shown in Fig. 3.5. The Megohmmeter has practical ranges capable of testing most modern plastics and other insulating materials upto 100 tera-ohms at four test voltages 100V, 250V, 500V and 1000V d.c. Resistance down to 100KΩ can be measured at voltage of 100V, and currents as low as 1 pico-ampere may be sensed. Typical applications for which MM29 is suitable include the measurement of discrete high value resistors and the insulation resistance measurement of materials, also of motors, switches, cables, capacitors, etc. On devices where one connection is earthed such as transformers and motors, measurements can be made, as also in terms where multiple resistance paths exist, e.g. in multi-core cables or multiposition switches. The instrument may be used as an accurate ammeter for general sensitive ammeter applications, the measurement of ionization and photomultiplication currents, semiconductor leakage currents and the leakage current in pre-stressed insulators. It may also be used as a d.c. voltage source or as a d.c. millivoltmeter. 3.4.2 DIELECTRIC CONSTANT AND TANGENT LOSS

Multifrequency 4284A ‘Hewlett Packard’ precision LCR meter is a high performance fully automatic test instrument designed to make measurements simple and much easier of various component parameter values of an impedance element in the relatively low frequency region, covering 20 Hz to 1 MHz with a basic accuracy of 0.1 %. It can measure inductance 10 nH to 100 KH, resistance, capacitance 0.01 pF to 100 mF, dissipation factor, quality factor, conductance, susceptance, reactance 10


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mΩ to 100 MΩ and, in addition, the absolute value of the vector impedance (|Z|) and phase angle (θ) over a wide range of frequencies with high accuracy (0.1 to 10 %) and speed (10 ns to 100 s). It makes the best of microprocessor advantages to achieve all measurements with versatility, sophisticated control and powerful calculation capabilities. The assembly diagram of the experimental set up is shown in Fig. 3.6. The versatile capabilities of the meter are maximized by the availability of the special test fixtures and the installation of options providing internal d.c. bias supply and memory back up. We have used this instrument for the measurement of capacitance and dissipation factor at temperatures from 25 oC to 300 oC and frequency from 100 Hz to 1 MHz. In a specially prepared sample holder, two plates of stainless steel work as electrodes between which sample is placed and cromel-alumel works as a thermocouple. The tip of thermocouple is placed near the sample. The sample holder (Fig. 3.7) with the sample held appropriately is placed into the furnace. The temperature of the furnace is measured by a digital temperature controller. 3.5 MAGNETIC SUSCEPTIBILITY MEASUREMENT

Many instruments6) are employed for measuring magnetic properties: Faraday force balance, Vibrating Sample Magnetometer(VSM), AC Susceptometer and SQUID magnetometer. All methods for the determination of magnetic susceptibility depend upon measuring the force resulting from the interaction between a magnetic field gradient and the magnetic moment induced in the sample by the magnetic field. The Magnetic susceptibility is a phenomenon that arises when a magnetic moment is induced in an object of an external magnetic field. It is the ratio of magnetization, M (magnetic moment per unit volume) to the applied magnetic field, H. The magnetic moment can be measured either by force method, which involves the measurement of the force exerted on the sample by an inhomogeneous magnetic field, or by induction method where the voltage induced in an electrical circuit is measured by varying magnetic moment.

The Gouy method6) (Faraday force balance) is a standard tool based on the

principle that when a sample with magnetic moment M is placed in a magnetic field gradient dH/dx, it will experience a force, F of magnitude

F= M * dH/dx The primary magnetic magnetizing field, H, is produced by a horizontal electomagnet. The field gradient is made to be along the vertical direction, so that magnetic force will add to (or substract from) the sample weight, and can be detected with a sensitive


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microbalance. In order to determine the magnetic susceptibility of a given test sample, it is first finely powdered and then packed in a Gouy tube, which is a glass container with known susceptibility, whose weight is exactly measured using Gouy balance. The Gouy tube hangs in between the poles of an electromagnet and the electromagnet is energized by a DC power supply. The distance between the pole pieces can be varied. A digital balance is placed which carries a hook at the bottom for suspending the glass tube containing the sample material. The magnetic field between the pole pieces can be varied by changing the current through the coils using a DC power supply, the corresponding magnetic field is measured with the help of a Gauss meter (GM 101). The calibration of applied magnetic field, H measured corresponding to dc current passed is obtained. The change in weight of the sample after applying magnetic field is measured for the calculation of magnetic susceptibility.

The Vibrating Sample Magnetometer (VSM) is one of the most versatile instruments. It uses an induction technique. The ‘Lake Shore’ 7304 4-inch electromagnet VSM system7) is used for the measurement of the magnetic moment on varying the magnetic field. When a sample material is placed in a uniform magnetic field, a dipole moment proportional to the sample susceptibility times the applied field is induced in the sample. A sample undergoing sinusoidal motion as well induces an electrical signal in suitably located stationary pick – up coils. This signal which is at the vibration frequency is proportional to the magnetic moment, vibration amplitude and vibration frequency. The sample is first finely powdered and then packed in a sample holder whose weight is exactly measured using digital balance. The material under study is contained in a sample holder which is centered in the region between the pole pieces of the electro-magnet. A slender vertical sample rod connects the sample holder with sturdy, adjustable support rods. The transducer converts a sinusoidal vertical vibration of the sample rod, and the sample is thus made to undergo a sinusoidal motion in a uniform magnetic field. Coils mounted on the pole pieces of the magnet pick up the signal resulting from the sample motion. This AC signal at the vibration frequency is proportional to the magnitude of the moment induced in the sample. A servo system maintains constancy in the drive amplitude and frequency so that the output accurately tracks the moment level without degradation due to variations in the amplitude and frequency of vibration. The DC output is an analog of the moment magnitude alone, uninfluenced by vibration amplitude changes and frequency drift. 3.6 INCIDENT LIGHT OPTICAL MICROSCOPE


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‘Carl Zeiss’ (Germany) ‘Epignost’ optical microscope shown in Fig. 3.8 is utilized for rapid examination of the ground, polished as well as the as-grown crystal surfaces. The study of dislocation etchpitting and the growth mechanism are made with the help of this microscope. The photomicrography is carried out at relatively lower magnification. It affords every convenience called for our investigations. The microscope and the illuminant are an entity not confined for use in any definite place. Being an incident light type of microscope, the objective has an infinite intersectional distance i.e. the specimen lies in the front focal plane of the objective and its image is formed at infinity. The instrument contains a permanently inbuilt tube lens which, together with the eyepiece, forms a telescope; thus resulting in a factor of 0.63 for calculating the total magnification. Magnification upto 250 can be attained in certain steps (using different objectives) with this microscope. But it suffers from a limitation that rapid change of objectives is not possible, due to lack of lever and knob arrangement. A 6V, 15 W filament pointolite lamp serves as the source of light. Monocular observation through different eye-pieces does not spoil the good contrast of the image. 3.7 MICROHARDNESS STUDIES

In order to study microhardness of crystals the point indentation technique is employed. The necessary equipment (MHT-10 Vickers sensor) for the purpose is to be attached to the ‘Carl Zeiss’ Metallurgical microscope, shown in Fig. 3.9. For the purpose Anton Paar’s MHT-10 Microhardness Tester with Video Measuring System is used. The specimen to be indented is mounted on a horizontal platform inserted in the collect. The area on the surface of sample is selected using bright field objectives for the indentation. Then an objective is replaced by Vickers microhardness indenter sensor from the rotating nosepiece. A required load is applied using Anton Paar’s MHT-10 Microhardness System. The diamond tip approaches the specimen surface at a defined speed which is specified by the control unit depending on the preselected force. The maximum speed can be limited to 70 µm/s. The diamond tip indents into the specimen at a preselected force gradient. The actual force is permanently measured and approaches the preselected value without overshooting. Upon completion of the dwell time, the diamond tip is automatically retracted to the resting position. The status LED flakes when measuring is running. The end of the measurement is signalized acoustically; after that the control unit selects the calculate mode. The diamond indenter marks the print on the sample surface. By reversing the motion, the indenter is removed and the indented region examined with the reading


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objective through the filer eyepiece or CCD camera interfaced to HCL computer. The diagonal of the indentation mark measured for different loads, is fed to the tester, and thus it shows directly the calculated value of the hardness on the screen. Further the index of refraction was measured by ‘Rajdhani’ ABBE Refractometer. 3.8 ABSOPTION SPECTROSCOPY 3.8.1 INFRARED (IR) SPECTROSCOPY

Infrared spectroscopy is the study of the interaction of light with matter. It is one of the most powerful analytical techniques which offers the possibility of chemical identification8). One of the most important advantages of infrared spectroscopy over the other usual methods of structural analysis is that it provides useful information about the structure of molecules quickly, without tiresome and lengthy evaluation methods. After absorption of IR radiations, the molecules of a chemical substance vibrate at many rates of vibration, giving rise to close – packed absorption bands, called an IR absorption spectrum which may extend over a wide wavelength range. Various bands will be present in IR spectrum, which correspond to the characteristic functional groups and bonds present in a chemical substance. Thus, an IR spectrum of a substance is a fingerprint for its identification. The increase in energy on account of IR absorption may be in the range of electronic, vibrational or rotational energy of the molecule. Changes in the electronic energy involve large quanta. Changes in the vibrational energy involve even smaller quanta while the changes in rotational energy involve even smaller quanta. If a molecule absorbs in the microwave or infra-red region, only its rotational energy will change, no matter which vibrational or electronic state it is in. If the radiation is in the medium infrared region, both the vibrational and rotational energies of the molecule will change. If the energy of the radiation is much greater as in the case of ultraviolet light, there will be changes in the electronic, vibrational and rotational energies of the molecule. In the present investigation, the infrared absorption spectrum was obtained on Spectrum GX (Perkin Elmer) single beam spectrophotometer. The sample was prepared in the form of a pellet, by taking about 3 mg of substance mixed with 1 gm of analytical grade dry potassium bromide. The mixture was finely powdered and then it was taken in a die. The die was assembled and evacuated to a pressure of 3 Torr. Then it was subjected to an extremely high pressure (about 1200 kg.cm-2) for about five minutes. This process resulted into the formation of fine pellet. The pellet was removed from the die and was used for scanning of the spectrum. The instrument was set for 100% transmittance. For recording the spectra, the sample was placed in one


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beam of the spectrophotometer and the relative intensity of the light energy transmitted versus wavelength or wave number is measured. ‘Nernst Glower’ is the common light source for IR radiation, consisting of a moulded rod containing a mixture of oxides of zirconium, yttrium and erbium, when heated electrically to around 1000 – 1800 0C. For obtaining monochromatic light, either optical prisms or gratings are used; grating spectrophotometers give higher resolution. For optical prisms and cell containers, glass or quartz cannot be used, for they strongly absorb throughout the IR region, while metallic halides (like sodium chlorides or potassium bromide) are commonly used for these purposes. 3.8.2 UV – VIS – NIR SPECTROSCOPY

For the chemical analysis of liquids, gases and solids, a laboratory instrument Lambda 19 Spectrophotometer ‘Perkin Elmer’ is used. The instrument provides a means for analyzing substances through the use of radiant energy in the ultraviolet to near infrared regions of the electromagnetic spectrum. Analytical information can be revealed in terms of transmittance, absorbance or reflectance of energy in the wavelength range from 185 to 3200 mµ. The instrument utilizes a single beam of energy, which is chopped into alternate reference, and sample beams to provide a double beam system with the sample compartment. To eliminate inaccuracy due to effects such as source fluctuations, changes in amplifier gain, sensitivity of spectral response of the detector and presence of common absorbing gases in the sample and reference path, ratio recording (comparison of sample beam energy with reference beam energy) is used.

Fig. 3.10 shows the path followed by a single ray within the radiation beam. The beam is reflected from the condensing mirror (A) to the slit entrance mirror (B), which directs the beam to the chopper (C). The chopped beam passes through the adjustable entrance slit (D) and into the monochromator. The beam is reflected from the collimating mirror (E) in parallel rays through a reflecting quartz prism (F), which disperses the beam into its spectrum of successive wavelengths. The back surface of prism is aluminized so that the beam is reflected back through the prism and further dispersed as it emerges. Rotation of prism relative to collimating mirror changes the angle of incidence and enables selection of a particular group of wavelengths that comprises a spectral band. This band of radiation is directed back to the collimating mirror, which focuses the entrance slit image on the exit slit (G). Upon passing from the monochromator, the radiation energy is directed by lens (H) into the double beam optical system in the sample compartment.


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This instrument is a double beam ratio recording spectrometer, i.e. radiant energies transmitted by the reference and sample beam (J and M) are compared, and the ratio of the sample energy to the reference energy is recorded as a percentage transmission. The double beam optical system consists of two synchronized semicircular rotating mirrors (I and N) and two stationary mirrors (L and K) in the sample compartment. The rotating mirrors consequently deflect and pass the radiant energy so that it is directed alternatively into the sample and reference cells 15 or 12.5 times per second. The detector focuses energy transmitted by the sample and reference cells.

For obtaining the absorption spectra, thin flake of approximately 1 mm thickness was used. It was pasted between two thick black papers with a cut exposing it to the incident light. The reference used is a replica of the black paper, having the cut in exactly same size as the crystal flake. This arrangement is necessary because the crystal size is smaller than that of the sample compartment. Detection of transmitted radiant energy requires two detectors to cover the entire wavelength range of the instrument. One - the lead sulphide cell (P) – that responds in the region between 400 to 3500 mµ. For measurements in the wavelength range extending below 700 nm, a photomultiplier tube (Q) is used. Radiant energy that strikes the detector is converted to a proportional alternating current signal.

REFERENCES

1) B.D.Cullity, Elements of X-ray diffraction, 2nd Edition, (Addision-Wesley Pub.Com., Inc. USA, 1978)

2) L. V. Azaroff, Elements of X-Ray Crystallography, (MaGraw Hill Book Company, NY, 1968)

3) J. L.Goldstein and H.Yokowitz, Practical scanning electron microscopy, (Plenum Press, New York, 1977)

4) John P Sibilia, A guide to Materials Characterization and Chemical analysis, (VCH Pub., Inc. NY, 1988)

5) C. Kittle, Introduction to Solid State Physics, 5th Edition, (John Wiley, NY, 1976)

6) L. N. Mulay and I. L. Mulay, “Static Magnetic Techniques and Applications,” in B. W. Rossiter and J. F. Hamilton (eds.), Techniques of Chemistry: Vol. I, Physical Methods of Chemistry, part IV, chap.2 (Wiley Interscience, New York 1972)

7) Lake Shore 7304 Series, Vibrating Sample Magneometer system, User’s Manual (1992)

8) Brian Smith, Infrared Spectral Interpretation (CRC press, Washington D.C.1999)


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Fig. 3.1 Schematic features of an X-Ray Diffractometer

Fig. 3.2 ‘Perkin Elmer’ TGA – 7 Instrument


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Fig.3.3 ‘Perkin Elmer’ DTA-7 Instrument Fig.3.4 ‘PerkinElmer’ DSC-7 Instrument

Fig. 3.5 Experimental set up for dc conductivity measurement using ‘MEGGER’


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Fig. 3.6 Experimental set up for capacitance measurement using ‘Hewlett Packard’ LCR meter

Fig. 3.7 Sample holder used for electrical conductivity/capacitance measurement

1.Sample 2.Electrode 3.Thermocouple 4.Porcelaine plate 5.Connector 6.Metal


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Fig. 3.8 Optical microscope ‘Epignost’ for microtopographic studies

Fig.3.9 Microhardness Tester, MHT-10 Vicker sensor with “Carl Zeiss”

Metallurgical microscope

Ch.3.Experimental Techniques

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Hydrogen lamp

Tungsten lamp

Photomultiplier tube

Lead sulphide cell

D

GF

H

J

A

B

K

I

c

L

MN

OP

Q

E

Fig. 3.10 The schematic diagram of UV-VIS spectrophotometer ‘Perkin Elmer’, Model:Lambda 19 GX

chapter 3 experimental techniquesshodhganga.inflibnet.ac.in/bitstream/10603/7346/9/09_chapter...

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