Thermal stability study of transition metal perovskite sulfides

Abstract

Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials.Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, a-SrZrS 3 , b-SrZrS 3 , BaZrS 3 , Ba 2 ZrS 4 , and Ba 3 Zr 2 S 7 . These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden-Popper phases.Differential scanning calorimeter and thermo-gravimetric analysis measurements were performed up to 1200°C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 600°C.

First–Principles Investigation of the Structural, Elastic, Electronic, and Optical Properties of α– and β–SrZrS3: Implications for Photovoltaic Applications

“…The band gap energies of αand β-SrZrS 3 are predicted at 1.38, and 1.95 eV, respectively. The predicted values are in close agreement with the estimated optical band gaps from diffuse-reflectance measurements: α-SrZrS 3 (1.52 eV) and β-SrZrS 3 (2.05 eV) [16]. It is evident from the projected density of states (Figure 5a,b) that the conduction band edge, in both phases, is dominated by Zr-d states.…”

“…We can see that clear differences between the assigned peaks of α-SrZrS 3 and β-SrZrS 3 , which is consistent with the difference in their lattice parameters. All the peaks in the simulated DFT spectrum match very closely with the experimental XRD measurement from the work of Niu et al [34], as shown (Figure 2b). We consider that the assigned reflection peaks in the DFT XRD spectrum may become useful in clarifying future experiments, for instance to distinguish between the α-SrZrS 3 and β-SrZrS 3 phases.…”

“…Compared to lead halide perovskites, chalcogenide perovskites materials are more environmentally friendly (component elements are earth-abundant and non-toxic) and possess superior electronic and optical properties, suggesting their potential ideal for low-cost tandem solar cell application. So far, a number of transition metal chalcogenide perovskites have been successfully synthesized experimentally and investigated theoretically [3,[13][14][15][16][17]. Sun et al [3] in their theoretical studies, predicted that the band gaps of CaTiS 3 (1.0 eV), BaZrS 3 (1.75 eV), CaZrSe 3 (1.3 eV), and CaHfSe 3 (1.2 eV) having the distorted perovskite structure are suitable for making single-junction solar cells.…”

“…The α-and β-SrZrS 3 phases both crystallize in the orthorhombic crystal structure with space group Pnma. The optical band gaps were estimated to be 1.52 and 2.05 eV for the α-SrZrS 3 , and β-SrZrS 3 phases, respectively, from diffuse-reflectance measurements [16]. Thermal stability investigations by Niu et al [20] on synthesized α-SrZrS 3 , β-SrZrS 3 , BaZrS 3 , Ba 2 ZrS 4 and Ba 3 Zr 2 S 7 show that these chalcogenide perovskites possess excellent thermal stability in air for a temperature range up to 550 • C [16].…”

“…The optical band gaps were estimated to be 1.52 and 2.05 eV for the α-SrZrS 3 , and β-SrZrS 3 phases, respectively, from diffuse-reflectance measurements [16]. Thermal stability investigations by Niu et al [20] on synthesized α-SrZrS 3 , β-SrZrS 3 , BaZrS 3 , Ba 2 ZrS 4 and Ba 3 Zr 2 S 7 show that these chalcogenide perovskites possess excellent thermal stability in air for a temperature range up to 550 • C [16]. The fundamental atomic-level insights into the mechanical and structural characteristics, as well as the electronic and optical features of SrZrS 3 materials, albeit, poorly understood and inconclusive.…”