Synthesis, structural and ferromagnetic properties of La1â€�?�ð�?�¥K𝑥MnO3 (0.0â‰�? ð‘�? 0.25) phases by solution combustion method

[摘要] We describe the solution combustion synthesis and characterization of La_{1â€�?�ð�?��?}K_ð‘�?MnO₃ (0.0 â‰�? ð‘�? â‰�? 0.25) perovskite phases, which is a low temperature initiated, rapid route to prepare metal oxides. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent LaMnO₃ compound crystallizes in the orthorhombic structure (space group 𝑃ð�?�ð�?��?�ð�?��?, No. 62). Potassium substituted compounds were crystallized with rhombohedral symmetry (space group ð‘�?�â€�?3c, No. 167). The ratio of the Mn³⁺/Mn⁴⁺ was determined by the iodometric titration. The Fourier transform infrared spectrum (FTâ€�?�IR) shows two absorption bands for Mnâ€�?�O stretching vibration (𝜈_s mode), Mnâ€�?�Oâ€�?�Mn deformation vibration (𝜈_b mode) around 600 cm^-1 and 400 cm^-1 for the compositions, ð‘�? = 0.0, 0.05 and 0.10. Four-probe electrical resistivity measurements reveal a composition controlled metal to insulator transition (ð‘�??_{Mâ€�?�I}}}$), the maximum ð‘�??_{Mâ€�?�I} was observed for the composition La_0.85K_0.15MnO₃ at 287 K. Room temperature vibrating sample magnetometer data indicate that for the composition up to ð‘�? = 0.10, the compounds are paramagnetic whereas composition with ð‘�? = 0.15, 0.20 and 0.25 show magnetic moments of 27, 29 and 30 emu/g, respectively.

[学科分类] 材料工程

[关键词] Perovskite;XRD;crystal structure;electrical properties;magnetic materials.