Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys

DOI: 10.5281/zenodo.17359760 This work is licensed under a Creative Commons Attribution 4.0 International License. This allows re-distribution and re-use of a licensed work on the condition that the author is appropriately credited and the original work is properly cited. Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. https://doi.org/10.5281/zenodo.17359760 CHAPTER 19 Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys Sunil Kumar Department of Physics, Government Post Graduate College, Bisalpur, Pilibhit 262201 Uttar Pradesh, India Corresponding author Email: [email protected] Received: 13 August 2025; Accepted: 13 October 2025; Available online: 15 October 2025 Abstract: Combining chalcogen elements usually selenium (Se), or tellurium (Te) sulfur (S), with other elements like tin (Sn), germanium (Ge), arsenic (As), indium (In) or antimony (Sb), produces chalcogenide glasses. The wide range of infrared transparency, nonlinear optical characteristics, and photonic uses of these glasses make them unique. These glasses can be prepared by using a number of techniques, including melt-quenching, vapour deposition and sol-gel but the melt-quenching approach is the most widely used. Analysis of various thermal parameters of chalcogenide glasses, including Tg (glass transition temperature) Tc (crystallization temperature), thermal stability parameter, Hruby Parameter, glass and crystallization activation energy for glassy and crystallization region, crystallization rate constant, enthalpy, etc by using DSC in non-isothermal conditions. Thermal transport properties of Sunil Kumar Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 276 chalcogenide glasses (CGs) thermal conductivity, thermal diffusivity and specific heat per unit volume are also observed by using transient plane source technique (TPS). Keywords: Differential scanning calorimetric (DSC), Thermal stability, Transient Plane Source Technique (TPS), Activation energy Thermal Conductivity and Thermal Diffusivity 1. Introduction Rapid cooling of melt to solidification prior to crystallization creates glassy solids. Although a glass has a random structure similar to that of a liquid, it has an extremely high viscosity (~10 13poise), which is almost the same as that of a solid (~1014.6poise). Because of a certain temperature known as the glass transition temperature, glasses vary from other non-crystalline materials. Rapid cooling below this temperature turns a liquid into glass. The VI group elements (S, Se, and Te) of periodic table are used to make chalcogenide glasses. These glasses function as semiconducting substances. The potential uses of these glasses in optical devices and solid-state electronics including, photolithography, non-linear optics, optical imaging, memory switching, phase change optical recording, and, have sparked interest in them in recent years.1–6 Digital X-ray imaging and TV pick-up tubes both use selenium-rich alloys. Long polymeric Sen chains are randomly combined to form amorphous Se with twofold coordination. Due to the size and the additional electrons in this orbit, Te causes modifications in interchain secondary bonds or Vander walls bonds when it is added to Se. The lower crystallization temperature, aging effect and lower thermal stability are characteristics the binary (CGs).7, 8 The addition of third element in binary (CG) work as chemical modifier and improve the thermal, optical and physical properties of theses glasses.9 As has been extensively explored in the literature, one method for examining crystallization kinetics is differential scanning calorimetry (DSC).10,11 Both isothermal and non-isothermal experiments can be used to study thermal changes in the glassy alloys.12,13 The heat evolved during the crystallization process is considered as a function of time in the isothermal system, which uses rapidly raising the sample's temperature above the Tg. In the non-isothermal method, the sample is heated at a fixed rate and the heat that forms is again measured as a function of temperature or time. The inability to instantly attain a test temperature and the inability to take measurements while the system is stabilizing are drawbacks of the isothermal technique. This disadvantage does not apply to an experiment with a constant heating rate.14 Finding the crystallization kinetics for a single alloy using several techniques is interesting. Impurity additions such as Sn are especially interesting since they have significantly altered the thermal, optical, and electrical, characteristics of (CGs). The manufacturing of the device, which may be altered by adding the tin (Sn), is largely dependent on the material's optical gap and lattice perfection. The crystallization kinetics and thermal stability of Se–Te–Sn-In multi-component (CGs) was reported by Kumar and Singh.15 Glass transition kinetics and thermal stability of Se90−xTe5Sn5Inx multi-component Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 277 (CGs) were reported by Singh and Kumar.16 The synthesis methods and thermal characteristics of chalcogenide glasses are covered in this chapter. 2. Synthesis Techniques for Chalcogenide Glasses (CGs) Although the melt quenching process is used to synthesis ChGs in bulk, thin film integration is necessary for the majority of ChG functional applications. According to the literature, there are a number of methods for creating chalcogenide glass in bulk and thin films. Certain devices, such as phase change memory devices, needed a thick, precisely thin film of a few nanometers to be deposited quickly and conformally coated.17-20 2.1. Melt Quenching Technique The process of melt quenching is essential when creating glasses. The necessary amounts of the high purity (99.999%) components for the melt quenching procedure were weighed using an electronic scale. The high-purity materials with the necessary mixture ratio of elements were sealed into quartz ampoules (length 5 cm and inside diameter 8 mm) under a vacuum of 10-6 Torr to guarantee the homogeneity of the samples. The ampoules were then heated to the required temperature in a furnace at a rate of 3–4 K/min, and they were kept there for 8–10 hours. The molten samples were then quenched with ice-cooled water. The quenched sample has the shape of glasses. The amorphous nature has been demonstrated by the X-ray diffraction pattern.16 2.2. Thin Film Techniques The literature has a number of thin film deposition methods that have been employed by various research communities. Based on their instrumentation and underlying physical and chemical principles of action, these approaches can be classified as either physical or chemical. Sublimation, evaporation, and ionic processes are examples of physical processes used in the physical vapor deposition (PVD) technology. When atoms are transferred from a solid or molten source onto a substrate, impingement is a crucial factor. These methods create thin films of elements, alloys, or compounds with thicknesses ranging from a few nanometers to micrometers. The two PVD processes that are most frequently employed are evaporation and sputtering. 2.2.1. Thermal Evaporation Technique Using a molybdenum boat and vacuum evaporation, thin films of a sample were applied to clean glass substrates while maintaining base pressure and the substrate at ambient temperature. Following a soap solution wash, trichloroethylene ultrasonography, and an acetone dip, the glass substrates were cleaned. Following a final cleaning with double-distilled water, the substrates were dried in an oven set at roughly 100°C. A quartzcrystal analyzer was employed to control the evaporation rates and film thickness. The films' thickness is μm. The thin films were kept at the proper temperature inside the deposition chamber to attain thermodynamic equilibrium, as advised by Abkowitz21 in chalcogenide glasses. In order to compare the results for various samples, the ambient conditions and deposition parameters were maintained Sunil Kumar Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 278 constant for each sample. A reference glass substrate was positioned in the path of one beam of a double beam spectrophotometer to measure the optical absorbance of films in the μm spectral band. 2.2.2. Flash Evaporation Technique Using a modified feeder in a coating machine, thin films of the sample were created using the flash evaporation technique on ITO-coated glass substrates at room temperature in a vacuum chamber at pressures lower than 5×10-6 mbar. A molybdenum boat was used to evaporate a 99.99% pure sample powder that was provided by Standard Company. The powder was put in one of the disk's bins. In order to evaporate the sample powder, it was moved into a boat that had been heated to a temperature of roughly 1500K. 40 nm and 800 nm thick thin films were made. Using an ultrasonic bath, the substrates were washed in acetone and methanol before being dried with nitrogen gas. Additionally, the substrates underwent glow discharge cleaning prior to sample deposition. About 15 centimeters separated the source from the substrate. The films were taken out of the coating chamber and let into the surrounding air after deposition.22 2.2.3. Sputtering Technique Atom by atom or in clusters, the surface atoms are physically removed off a solid surface by the momentum transfer of gaseous ions accelerated from plasma to create high-quality thin films. The process of vaporization is not thermal. This process has a shorter source-to-substrate distance than the vacuum deposition method. To use this deposition method, an intensive ion bombardment of a sputtering target in a high vacuum setting using an ion gun or low-pressure plasma. With this method, the sputtered particle experiences infrequent or no gas phase contacts between the target and the substrate. Wenpeng Chen and A. van der Jagt A thin layer of Tl2SeAs2Te3 chalcogenide glass was created using this method.23 The earliest methods of sputtering are also magnetron, DC, and radio frequency sputtering. 2.2.4. Chemical Vapour Deposition Technique This method involves transporting the gaseous chemical reactants to the reaction chamber (around the substrate) using thermally triggered or other means (such as plasma-assisted CVD or laser-induced CVD) so that the reaction can create a thin film on the substrate surface. Even on surfaces with complex forms, homogeneous films with low porosity can be deposited with this method. The main prerequisite for using this method to create thin films is a high vacuum. Numerous alternative techniques, such as the glow discharge method, spin coating technique, pulsed laser deposition technique, etc., can be used to create thin films from bulk materials.24,25 2.2.5. Glow Discharge Decomposition Technique This method is based on the formation of plasma in a low-pressure gas, just like sputtering, but instead of ions from the plasma ejecting material from the target, the gas itself undergoes a chemical breakdown, which leads to the deposition of a thin film on a plasma-preserved substrate. The plasma is created by applying an r.f. field using either an inductive or capacitive connection. The film deposited with this Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 279 technique is significantly influenced by the gas pressure, flow rate, substrate temperature, and chamber geometry.26 2.2.6. Spin Coating Method Curry and Mairaj27 used the spin coating technique to create a thin layer of chalcogenide glass in 2005. The fluid's deposition onto the substrate and the subsequent removal of the coated substrate are the two processes that go into making an amorphous thin film. The film thickness can be increased by the same amount or decreased by an order of magnitude by changing the experimental conditions. The composition can be changed to change the viscosity of glass.28 2.2.7. Pulsed Laser Deposition Technique Thin films were produced using pulsed laser deposition (PLD) on chalcogenide targets. Initially, bulk samples were made by synthesizing directly from pure components of evacuated silica ampoules.29 Samples were then sliced and polished to produce parallel-faced PLD targets after this process. The thin films were deposited on static substrates at room temperature. Si substrates were cleaned with ethanol and acetone using ultrasonic vibration prior to being put in the deposition chamber. The films were deposited using a vacuum. The laser beam's angle of incidence was selected to provide constant target ablation. Pulsed laser deposition (PLD) creates a plasma plume of the target material by ablation of the target's surface using a short laser radiation pulse. When the plume comes into contact with the substrate, its contents may cover it. Many studies have looked into the creation of thin films using pulse laser deposition technology. Numerous chalcogenide material types have been formed using this method.30 3. X-Ray Diffraction The X-ray diffraction pattern reveals the presence of several phases within the substance. Crystalline materials exhibit significant crystalline peaks in patterns of X-ray diffraction due to the systematic arrangement of their atoms. The X-ray diffraction patterns found in amorphous or non-crystalline materials, however, exhibit a broad hump. This significant hump in the X-ray diffraction pattern of an amorphous solid is caused by random or uneven atomic distribution inside materials. (see Fig.1). Fig. 1. XRD pattern of a particular chalcogenide glass Sunil Kumar Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 280 4. Thermal Properties Differential Scanning Calorimetry (DSC) Calorimetry was used to study the thermal properties of solids for over 100 years. It is still thought to be among the best methods for determining the kind of phase transitions that occur in glassy materials. Although calorimeters come in a wide variety nowadays, they can be broadly categorized into two groups. Devices in the first category measure the heat transfer between a sample and a thermal block while continuously adjusting the calorimeter's temperature. Most of them need a dummy sample (differential scanning calorimeter, DSC) in order to function differentially.The term "non-isothermal mode" describes these DSC observations. The calorimeters in the second group adiabatic, relaxation and ac calorimeters measure the sample's temperature when a very small quantity of heat is applied. The calorimeter's temperature is maintained during the measurement in these kinds of DSC equipment. First-order phase transitions are specifically investigated in DSC. DSC curve of particular glassy alloys at heating rate 15 K/min is shown in Fig. 2. The first endothermic-like phenomenon indicates the glass transition region, which arises due to an abrupt increase in the specific heat of the sample. The second is the exothermic peak, which arises due to the crystallization process of the sample. Fig. 2 shows that the glass transition temperature (Tg) crystallization temperature (onset) Tc and crystallization temperature (peak)Tp and (Tc-Tg) thermal stability. Fig. 2. DSC thermograms of the particular chalcogenide glasses at 15K/min heating rate. Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 281 Set-up description Differential scanning calorimetry, or DSC, is a technique for calculating the energy needed to produce almost zero temperature differences between a substance and an inert reference material. Following exposure to the identical temperature regimes in a controlled-rate heated or cooled environment, the two specimens are displayed in Fig. 3. In this type of DSC, the sample and reference are connected by a lowresistance heat flow path. A single furnace covers the assembly. The sample's temperature differs from the reference due to changes in enthalpy or heat capacity. The observed temperature differential is connected to the enthalpy change. Fig. 3. A schematic framework Heat flux DSC Working Principle of DSC In heat flux DSC, the reference and sample pans are stored in the same furnace. The difference in heat required to maintain the reference and sample at a nearly equal temperature causes the sample to undergo thermal change because of excessive energy conduction between them though an attached metallic disc. Because the temperature differential that forms between the sample and the inert reference pans corresponds to the heat flow between them, the system's thermal resistances vary with temperature. This shift was recorded in calibrated mode, which automatically adjusts the amplification with temperature to offer a nearly constant calorimetric sensitivity. Because the sample material is not in close contact with the thermocouples, several temperature variations between the specimen and thermocouples occur during the operation. Consequently, the precise T is not equal to 0 0RS TT − , where 0 R T and 0 S T are the temperatures of reference and sample respectively. The 0 0RS TT − deduce from allowing for the heat flow paths in the system, as block diagram shown in Fig. 4. Sunil Kumar Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 282 Fig. 4. A schematic framework of a Heating block of DSC The used terminologies are defined as; s T , r T = Temperature of the sample and reference platform in that order. TSp normally plotted as the abscissa of a DSC curve. f T = Temperature of the silver heating block. d R =Thermal resistance between the furnace wall and the sample or reference Platforms (units Cmin J-1). 0 S R , 0 R R = Thermal resistances between the sample and reference platform. 0 S C , 0 R C = Heat capacity of the sample and reference with particular containers. H = Imposed heating rate. 0 R T = Temperature lags of the reference platform relative to furnace. 0 S T = Temperature lags of the sample platform comparative to furnace. 0 l T = Temperature lags of the sample comparative to the sample thermocouple. 0 R T = 0 Rd CHR (1) 0 S T = 0 SdCHR (2) T = ( ) 0 0RSd CCHR − (3) Synthesis Techniques and Thermal Properties of Chalcogenide Glassy Alloys Materials Science: Advances in Synthesis, Characterization and Applications (Vol. 1) - Digambar M. Sapkal, Harshal M. Bachhav, Gaurav Mahadev Lohar, Sanjay P. Khairnar (Eds.) ISBN: 978-93-95369-55-8 (paperback) 978-93-95369-46-6 (electronic) | © 2025 Advent Publishing. 283 0 l T = 0 0SS CHR (4) 0 S T = TTR+ 0 (5) 0 l T = 0 0 Sd S TR R  (6) Temperature Calibration Under the DSC furnace configuration, the temperature curve has been drawn on the abscissa of a DSC data that corresponds to the emf produced by the thermocouples. Using identified calibration tables, the emf can be accurately converted to temperature units for normal thermocouple conditions. Calorimetric Calibration Measurements of the sample's changes in specific heat or enthalpy are used to perform calorimetric calibration. Equation (2) can be used to define the change in specific heat in order to use the DSC device in calibrated mode. The heat flux DSC system's balancing heat equation is as follows: ( ) 0 00 SRS d rs CHCC R TT dt Hd +−+ − =       −        + dt TT d R RR rs d Sd 0 (7) dt Hd  refers to the heat evolution of an exothermic transition; the first term on the right displays the area under the DSC peak with the baseline correction value. The second term on the right is the actual baseline that is utilized to determine specific heat. The third term, which is independent of the DSC peak area but could distort the peak form, explains that the specimen will use some of the evolved heat to heat itself. Equation (7) makes it evident that the second term can be utilized to calculate specific heat when the dt Hd  value of is equal to zero. By comparing the thermal lag of the reference and sample DSC pans, the approach can be used. To do this, the system must first be calibrated using a standard specimen that comes with the equipment. 00MH YE Cq = (8) where M0 is the mass of the sample, E is a calibration stable, C is the specific heat capacity of the standard sample, q is the Y -axis range and term Y is the variation in deflection between actual sample and standard sample. The enthalpy changes can be resolute by measuring the area under peak of the DSC curve. After all plot a relation ΔT against time, which verify the equation (1).