Insights on the Synthesis, Crystal and Electronic Structures, and Optical and Thermoelectric Properties of Sr1- xSbxHfSe3 Orthorhombic Perovskite

Moroz, Nicholas A.,Bauer, Christopher,Williams, Logan,Olvera, Alan,Casamento, Joseph,Page, Alexander A.,Bailey, Trevor P.,Weiland, Ashley,Stoyko, Stanislav S.,Kioupakis, Emmanouil,Uher, Ctirad,Aitken, Jennifer A.,Poudeu, Pierre F. P.

, p. 7402 - 7411 (2018)

Single-phase polycrystalline powders of Sr1-xSbxHfSe3 (x = 0, 0.005, 0.01), a new member of the chalcogenide perovskites, were synthesized using a combination of high temperature solid-state reaction and mechanical alloying approaches. Structural analysis using single-crystal as well as powder X-ray diffraction revealed that the synthesized materials are isostructural with SrZrSe3, crystallizing in the orthorhombic space group Pnma (#62) with lattice parameters a = 8.901(2) ? b = 3.943(1) ? c = 14.480(3) ? and Z = 4 for the x = 0 composition. Thermal conductivity data of SrHfSe3 revealed low values ranging from 0.9 to 1.3 W m-1 K-1 from 300 to 700 K, which is further lowered to 0.77 W m-1 K-1 by doping with 1 mol % Sb for Sr. Electronic property measurements indicate that the compound is quite insulating with an electrical conductivity of 2.9 S/cm at 873 K, which was improved to 6.7 S/cm by 0.5 mol % Sb doping. Thermopower data revealed that SrHfSe3 is a p-type semiconductor with thermopower values reaching a maximum of 287 μV/K at 873 K for the 1.0 mol % Sb sample. The optical band gap of Sr1-xSbxHfSe3 samples, as determined by density functional theory calculations and the diffuse reflectance method, is ～1.00 eV and increases with Sb concentration to 1.15 eV. Careful analysis of the partial densities of states (PDOS) indicates that the band gap in SrHfSe3 is essentially determined by the Se-4p and Hf-5d orbitals with little to no contribution from Sr atoms. Typically, band edges of p- and d-character are a good indication of potentially strong absorption coefficient due to the high density of states of the localized p and d orbitals. This points to potential application of SrHfSe3 as absorbing layer in photovoltaic devices.

Bayliss, S. C.,Liang, W. Y.

, (1982)