Novel Zintl phases exhibiting promising thermoelectric properties have garnered considerable traction, largely attributed to the accuracy of computational estimates. In the present investigation, the density functional theory-based WIEN2k code is employed to analyze the structural, optoelectronic, and transport behavior of the BaAg2X2 (X = S, Se, Te) Zintl phase. All these compositions belong to the stable trigonal phase with nominal expansion in the unit cell with the replacement of S with Se and Te. A negative value of enthalpy of formation of -2.30, -2.0, and -1.80 for BaAg2S2, BaAg2Se2, and BaAg2Te2, respectively, assures their thermodynamic stability. These compositions demonstrate dynamic stability, as evidenced by the nonexistence of negative (-ve) frequency values in their phonon spectra. Increasing the size of chalcogens enhances the spin-orbit coupling and reduces the bandgap value from 2.10 - 1.55 eV. The examination of optical response suggests that studied compositions display high absorption and low energy loss in the visible range, rendering them suitable for optoelectronic devices. The temperature-dependent transport behavior is computed using BoltzTrap code, and the RT value of power factor is recorded as 0.89 × 1011, 0.65 × 1011, and 0.54 × 1011 Wm− 1K− 2 for BaAg2X2 (X = S, Se, Te). A high power factor value at elevated temperatures indicates the promising efficacy of studied compositions in thermoelectric device applications.
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