Structural, Electrical, and Magnetic Properties of High-Temperature-Sintered La1-xNaxMnO3 (0.05 <= x <= 0.35) Compounds

Abstract

The structural, electric, and magnetic properties of La1-xNaxMnO3 (0.05 <= x <= 0.35) compounds have been investigated. The compounds were prepared by a standard sol-gel method then sintered at 1400 degrees C for 24 h. The crystal structures were orthorhombic (Pbnm) for all Na concentrations, and the unit cell volumes, determined from the x-ray diffraction data, tended to decrease with increasing Na content. The high-temperature-sintering process resulted in a grainy structure with grain sizes of 5-30 mu m. The Curie temperature (T-C) increased with increasing Na concentration up to x = 0.20, then decreased with further increase in Na concentration. The maximum magnetic entropy change (-Delta S-M) under a field change of 1.6 T was calculated to be similar to 3 J/kg K for the sample containing 15% Na.