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In this study, we have demonstrated the application of sodium manganese oxide for the chemisorption of toxic acidic gases at room temperature. The fabricated alkali ceramic has Na 0.4 MnO 2 , Na 2 Mn 3 O 7 , and Na x MnO 2 phases with a surface area of 2.6 m 2  g -1 . Na-Mn oxide was studied for oxidation of H 2 S, SO 2 , and NO 2 gases in the concentration range of 100-500 ppm. The material exhibited a high uptake capacity of 7.13, 0.75, and 0.53 mmol g -1 for H 2 S, SO 2 , and NO 2 in wet conditions, respectively. The material was reusable when regenerated simply by soaking the spent oxide in a NaOH-H 2 O 2 solution. While the H 2 S chemisorption process was accompanied by sulfide, sulfur, and sulfate formation, the SO 2 chemisorption process yielded only sulfate ions. The NO 2 chemisorption process was accomplished by its conversion to nitrite and nitrate ions. Thus, the present work is one of the first reports on alkali ceramic utilization for room-temperature mineralization of acidic gases., (© 2023. The Author(s).)

We report composition dependent structure evolution from SrTiO3 to SrFe0.5Ta0.5O3 by powder X-ray and neutron diffraction studies of SrTi1-2xFexTaxO3 (0.00 ≤ × ≤ 0.50) compositions. Structural studies reveal cubic (Pm3m) perovskite-type structure of the parent SrTiO3 for x up to 0.075 and cation disordered orthorhombic (Pbnm) perovskite-type structure for x ≥ 0.33. A biphasic region consisting of a mixture of cubic and orthorhombic structures is found in the range for 0.10 ≤ × ≤ 0.25. Dielectric studies reveal transformation from a normal dielectric to relaxor like properties with increasing Fe(3+) and Ta(5+) concentration. Dielectric response is maximum at x = 0.33 in the series. The results establish a protocol for designing new lead-free relaxor materials based on the co-substitution of Fe(3+) and Ta(5+) for Ti(4+) in SrTiO3. A complex interplay of strain effects arising from distribution of cations at the octahedral sites of the perovskite structure controls the dielectric properties.