Thermal Transport and Mechanical Properties of Layered Oxychalcogenides LaCuOX (X = S, Se, and Te)
Ning Wang, Chen Shen, Zhehao Sun, Bingke Li, Haiyan Xiao, Xiaotao Zu, Hongbin Zhang, Zongyou Yin, Liang Qiao
Abstract
Layered LaCuOX (X = S, Se, and Te) have great potential for high-performance photoelectric (PE) applications, while little is known about their mechanical and thermal properties. The lack of this information will hinder understanding their transport mechanisms and applications as high TE/PE energy conversion efficiency devices. This study investigates the electronic, mechanical, and thermal properties of LaCuOX compounds. The investigated tetragonal crystals are all found to be mechanically stable. Besides, the mechanical stability and stiffness of layered LaCuOX weaken from LaCuOS to LaCuOTe, while their shear strain resistances are comparable. All the materials show good ductility and have ionic–covalent bonding. Since the Debye temperature and sound velocity decrease from LaCuOS to LaCuOTe, the thermal conductivity increases following the same order. Due to large Grüneisen parameters caused by strong phonon anharmonicity, ultralow thermal conductivities of LaCuOS, LaCuOSe, and LaCuOTe are found to be 2.58, 2.20, and 1.90 W/m K at 300 K, respectively. This work deepens the understanding of the physical properties of LaCuOX crystals, which may benefit in promoting their potential PE and thermoelectric applications.