Browsing by Author "Devanand Gupta"

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Effect of Bi modification on structural and dielectric properties of selenium-rich Se-In chalcogenide glasses
(Elsevier Ltd, 2025) Himanshu Meena; Saurabh Mishra; Devanand Gupta; Baniya R. Meena; Horesh Kumar
This work focuses on the structural and electrical characteristics of Se90In10-xBix (x = 0, 2, 4, 6, and 8) chalcogenide alloys that were synthesized using the traditional melt quenching method. The X-ray diffraction patterns of the prepared samples show that they are polycrystalline in nature. Transmission electron microscopy (TEM) backs the XRD phase identification and shows the formation of nanorods and nanoparticle clusters, which increase with the increasing bismuth concentration. Raman spectroscopy is used to further support the structural aspects, which were established by XRD and TEM analysis. In Se90 in10-xBix glass, the band gap decreases on increasing the Bi content, and the lowest band-gap value is observed in Se90In2Bi8 chalcogenide, which is attributed to the larger crystallite size. Measured electrical properties, such as dielectric constant, dielectric loss, and electrical conductivity, were found to depend on temperature (309–348 K) and frequency (100 Hz - 1 MHz). The undoped binary Se-In sample has the lowest dielectric constant and loss values at a given frequency and temperature, but with increasing Bi incorporation, an increment in dielectric constant and loss values is observed. For sample x = 6 (Se90In4Bi6), the maximum values of dielectric constant and loss are noted. On inclusion of Bi in place of In in the studied system, the conductivity of the sample increased significantly, and the highest conductivity value was noted for sample x = 6. Also, a change in the conduction mechanism was observed from the CBH model with IVPA to the CBH model with NVAP © 2025 Elsevier Ltd and Techna Group S.r.l.
Investigation of impact of antimony (Sb) nanoparticles incorporation on structural, dielectric, and electrical properties of Se76-xGe14As10Sbx (x = 0, 3, 6, 9, and 12) glasses
(Elsevier Ltd, 2025) Vijay Pratap; Surya Pratap; Devanand Gupta; Horesh Kumar
Chalcogenide glasses of composition Se76-xGe14As10Sbx (x = 0, 3, 6, 9, and 12 %) were prepared using Sb nanoparticles by traditional melt quenching procedure. Structural analysis reveals that Sb forms bonds with Se at lower atm.%, however, at higher atm.%, other heteropolar bonds are also formed. Their dielectric properties and a.c. conductivity were studied in the frequency range of 20.20 – 1010.10 kHz and the temperature range of 300 – 345 K, respectively. A temperature and frequency dependence of the dielectric constant was observed, indicating orientation polarization in the system. The dielectric constant increases with the incorporation of Sb nanoparticles. However, a slight decrease is noticed for x = 12. The variations in dielectric loss with temperature and frequency were explained by polaron hopping of charge carriers and conduction loss, as per the Elliot and Shimakawa hypothesis. The a.c. conductivity was found to be ∼ 10−4 (Ω-m)−1 for prepared alloys. The conduction mechanism shows a change from Correlated Barrier Hopping (CBH) to the Non-Overlapping Polaron Tunneling (NSPT) at a particular temperature for all the alloys. © 2025 Elsevier B.V.
Structural and optical studies of chalcogenide (Ge22As20Se58) doped with rare-earth Eu3+and Y3+ ions
(Springer, 2025) Amarendra Kumar Singh; Devanand Gupta; Sanjay Kumar Mishra; Horesh Kumar
This study investigates the effects of rare earth ion doping (Eu3+-doping, Y3+-doping, and Eu3⁺–Y3⁺ codoping) on the structural and optical properties of Chalcogenides (Ge22As20Se58) using the melt-quench approach. Structural and optical characterization studies, such as XRD and TEM study reveal that rare-earth doping enhances the amorphous character, with codoping leading to highest amorphosity. FTIR analysis suggests that codoping improves mid-infrared transmission transmission beyond 90%, attributed to reduced phonon energy and optimized local bonding. Further, Raman spectra investigation indicates dopant interaction with selenium atoms and modifications in vibrational modes in the glass samples. The UV–Vis DRS study confirms dual optical band gaps, with a transition from direct to indirect bandgap upon doping. While single doping reduces the bandgap due to increased disorder, codoping leads to a slight increase in bandgap compared to singly doped samples, suggesting reduced crystallinity and restricted resonant bonding. Moreover, these results provide information on tailoring the structural and optical characteristics of Eu3⁺–Y3⁺ codoped chalcogenide glasses, which can be explored further in photonic and optoelectronic applications. © The Author(s), under exclusive licence to The Optical Society of India 2025.
Structural, dielectric and electrical properties of Se96−xSn4Sbx(x = 0, 2, 4, 6, and 8) glassy alloys
(Elsevier Ltd, 2023) Rafiullah Ansari; Devanand Gupta; Horesh Kumar
Structural, dielectric and electrical properties of the Se96−xSn4Sbx (x = 0, 2, 4, 6, and 8) glassy alloys, which were prepared by conventional melt quench technique were investigated. The binary sample (x = 0) is polycrystalline, consisting of nanorods stuck with nanoparticles, while the ternary samples (x = 2, 4, 6, and 8) are amorphous. Measured properties, such as the dielectric constant, loss, and conductivity, are found to be functions of temperature and frequency. Dielectric constant and loss are maximum for x = 0 composition and decreased significantly on the inclusion of Sb (ternary compositions). DC and AC conductivities are thermally activated processes for all compositions. With the addition of Sb in place of Se in the studied system, both conductivities have been reduced by several orders of magnitude, accompanied by a change in the conduction mechanism from the CBH model with NVAP to the CBH with IVPA. © 2022 Elsevier B.V.
Thermal, optical, dielectric and electrical transport properties of nano-structured Se95-xIn5Prx (x = 2, 4, and 6) glassy alloys
(Elsevier Ltd, 2023) R. Ansari; Devanand Gupta; Pankaj K. Mishra; A.L. Saroj; H. Kumar
In the present study, Se95-xIn5Prx (x = 2, 4, and 6) alloys were prepared using the melt quench technique. X-ray diffraction (XRD) and Raman spectroscopy reveal that the glassy matrix of each sample consists of crystalline entities identified as a mixed phase of indium selenide (HCP) and praseodymium selenide (FCC). TEM images show that the crystalline entities are nanorods stuck to nanoparticles. The thermal stability and optical band gap (direct) decrease (1.974 eV to 1.425 eV) with Pr content. The dielectric constant and loss are maximums for x = 4 at any frequency and temperature (30°C-60 °C). AC conductivity follows the correlated barrier hopping (CBH) model (frequency exponent s<1, and decreases with temperature) with non-intimate valence alteration pairs (NVPA) for x = 2 and 6, and intimate valence alteration pairs (IVPA) for x = 4. AC activation energy decreases with Pr concentration at all frequencies in the study range. © 2023