Doping GeSb₂Te₄ with Cr³⁺: Structure and Temperature‐Dependent Physical Properties

Abstract

Abstract The tellurides Ge 0.94 Cr 0.04 Sb 2 Te 4 and Ge 0.88 Cr 0.08 Sb 2 Te 4 were synthesized in sealed silica glass ampoules. Rietveld refinements show that they crystallize in the 21 R ‐In 3 Te 4 structure type ( R m ), similar to undoped GeSb 2 Te 4 . The composition and phase purity were confirmed by ICP‐AES as well as by SEM and TEM, including EDX measurements. EPR spectroscopy reveals the valence state +III for the Cr atoms ( g = 1.990) in Ge 0.88 Cr 0.08 Sb 2 Te 4 , which agrees well with the Cr 3+ content calculated from the inverse magnetic susceptibility. The material exhibits a ferromagnetic fluctuations with a paramagnetic Curie temperature of 70 K ± 20 K and is a metallic conductor. Compared to GeSb 2 Te 4 , the electrical conductivity is increased by a factor of 2.5. As Cr doping further leads to a higher Seebeck coefficient, the thermoelectric figure of merit ZT reaches values of up to 0.3 at 500 °C, i.e. three times the value of undoped material.