Sb concentration dependent structural and resistive properties of polycrystalline Bi-Sb alloys

TL;DR

This study investigates how varying antimony concentration affects the structural and electrical properties of polycrystalline Bi-Sb alloys, revealing a transition from direct to indirect band gap around 12% Sb content.

Contribution

It provides detailed structural analysis and establishes the relationship between Sb concentration, lattice parameters, and electronic band structure in Bi-Sb alloys.

Findings

Lattice parameters decrease with increasing Sb content.

Maximum band gap occurs at 12% Sb.

Transition from direct to indirect band gap near 12% Sb.

Abstract

Polycrystalline Bi-Sb alloys have been synthesized over a wide range of antimony concentration (8 at% to 20 at%) by solid state reaction method. In depth structural analysis using X-Ray diffraction (XRD) and temperature dependent resistivity measurement of synthesized samples have been performed. XRD data confirmed single phase nature of polycrystalline samples and revealed that complete solid solution is formed between bismuth and antimony. Rietveld refinement technique, utilizing MAUD software, has been used to perform detail structural analysis of the samples and lattice parameters of synthesized Bi-Sb alloys have been estimated. Lattice parameter and unit cell volume decreases monotonically with increasing antimony content. The variation of lattice parameters with antimony concentration depicts a distinct slope change beyond 12 at% Sb content sample. Band gap has been estimated from the thermal variation of resistivity data, with the 12% Sb content sample showing maximum value. It has been observed that, with increasing antimony concentration the transition from direct to indirect gap semiconductor is intimately related to the variation of the estimated lattice parameters. Band diagram for the polycrystalline Bi-Sb alloy system has also been proposed.