Based on first-principles calculations,Boltzmann transport equation and semiclassical analysis,we conduct a de-tailed study on the lattice thermal conductivity κL,Seebeck coefficient S,electrical conductivity σ,power factor S2σ and dimensionless figure of merit,zT,for K3IO.It is found that K31O exhibits relatively low lattice thermal conductivity of 0.93 W·m-1·K-1 at 300 K,which is lower than the value 1.26 W·m-1·K-1 of the classical TE material PbTe.This is due to the smaller phonon group velocity vg and smaller relaxation timeτλ.The low lattice thermal conductivity can lead to excellent thermoelectric properties.Thus maximum zT of 2.87 is obtained at 700 K,and the zT = 0.41 at 300 K indicate that K31O is a potential excellent room temperature TE material.Our research on K3IO shows that it has excellent thermoelectric properties,and it is a promising candidate for applications in fields in terms of thermoelectricity.