Rotational speed effect of the planetary ball milling on the particle size and crystal structure of CaMnO3 as a thermoelectric material.

CaMnO3 (Calcium Manganese Oxide) is a ceramic material from oxide that promises N-type thermoelectric. The CaMnO3 was synthesized using the solid-state reaction method by mixing the CaCO3 and MnO2 powder as raw materials then milling in the planetary ball mill. The rotational speed variations of the planetary ball mill were 148 rpm, 170 rpm, 192 rpm, and 212 rpm. The purpose of this research is to study the effect of rotational speed on the crystal structure and particle size of CaMnO3, characterized by X-Ray Diffractions (XRD) and measured by Particle Size Analyzer (PSA). The X-ray diffraction pattern showed that CaMnO3 crystals had formed at the diffraction angle of 33.8971°, which indicated an Orthorhombic crystal system. On the other hand, the new phase peaks are found at the diffraction angle of 23.8145° indicating the presence of the Dicalcium manganate (Ca2MnO4) as a secondary phase. The intensity peak of CaMnO3 increases with the rotational speed, followed by the particle size and influencing the reduction of the Dicalcium manganate phase. The increased rotational speed in the milling process result in varying ball movements and influencing the crystal structure and particle size. The relationship between the rotational speed, the crystal structure and particle size will be discussed further in this study. [ABSTRACT FROM AUTHOR]