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ARTICLE

Influence of Germanium Substitution on the DC Electrical Properties and Energy Density of States in Pb_50−xGe_xTe₅₀ Ternary Chalcogenide Alloys

Muayed Khaleel Ibrahim¹, Shaymaa Hashim Aneed², Nidhal Saleh Mohammed², Kareem Ali Jasim², Mudatheer M. Al-Slivani^3,*

1 Department of Energy Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq
2 Department of Physics, College of Education for Pure Sciences, Ibn Al-Haitham, University of Baghdad, Baghdad, Iraq
3 Department of Physics, College of Education for Pure Sciences, Al-Furqan University, Mosul, Iraq

* Corresponding Author: Mudatheer M. Al-Slivani. Email:

(This article belongs to the Special Issue: New Horizons in Structural Design and Experimental Synthesis of Chalcogenide-based Materials for Energy Storage and Conversion)

Chalcogenide Letters 2026, 23(7), 1 https://doi.org/10.32604/cl.2026.082607

Received 19 March 2026; Accepted 04 June 2026; Issue published 07 August 2026

Abstract

This study investigates the structural evolution and DC electrical properties of Pb_50−xGe_xTe₅₀ ternary chalcogenide alloys with varying germanium concentrations (x = 5, 10, 15, 20). Synthesized via the melt-quenching technique, the alloys were characterized using Scanning Electron Microscopy (SEM) and temperature-dependent electrical resistivity measurements within the range of 290–475 K. Microstructural analysis revealed that increasing Ge substitution significantly promotes matrix densification, reducing porosity and improving inter-granular connectivity. The DC conductivity exhibits a systematic increase with Ge content up to x = 15, attributed to the increased density of defect states. For instance, as Ge content increases from x = 5 to x = 15, the DC conductivity increases, corresponding to an activation energy (ΔE₁) shift from 0.203 eV to 0.281 eV at high temperatures. However, for the sample with x = 20, a non-monotonic shift in conductivity parameters is observed, evidenced by a significant reduction in the pre-exponential factor ( σ 01 ) compared to the intermediate compositions, which indicates a alteration in the conduction pathways. The conduction data were analyzed using the Mott and Davis model, identifying three distinct mechanisms: hopping between localized states near the Fermi level at low temperatures, hopping within band-tail states at intermediate temperatures, and excitation into extended states at high temperatures. Furthermore, calculations of the density of states (DOS) indicated that Ge incorporation increases the density of extended and localized states while simultaneously narrowing the band tail width ( Δ E ), thereby reducing structural randomness. These findings highlight the efficacy of germanium doping in tuning the electronic structure of Pb-Ge-Te alloys, suggesting their suitability for advanced optoelectronic and semiconductor applications.

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