Post-ball-milling-assisted solid-state synthesis of Bi4O4SeCl2: A low thermal conductivity material

Abstract

This study investigates the synthesis of Bi4O4SeCl2 through a cost-effective ball-milling-assisted solid-state reaction method. The as-grown samples predominantly consisted of the Bi12O15Cl6 phase, with minor contributions from BiOCl and Bi4O4SeCl2. A systematic post-ball-milling process was applied to enhance the formation of the Bi4O4SeCl2 phase. Prolonged milling time led to the progressive dominance of the Bi4O4SeCl2 phase, resulting in significant improvements in electrical conductivity and reductions in thermal conductivity. After 30 min of milling, the carrier concentration increased notably from −2.23 × 1016 cm−3 (as-grown) to −1.01 × 1018 cm−3, while electrical conductivity rose from 0.14 S/cm (as-grown) to 2.26 S/cm. Simultaneously, thermal conductivity decreased from 0.65 W m−1 K−1 (as-grown) to 0.35 W m−1 K−1. These findings demonstrate that post-ball-milling is a scalable and economical method for synthesizing Bi4O4SeCl2 with low thermal conductivity, highlighting its potential as a promising material for thermal barrier coatings and thermoelectric applications.