Study of dielectric temperature spectrum characteristics for lithium hydride with defects based on the first principles calculations

Due to its lightweight and strong neutron shielding, lithium hydride (LiH) is a potential candidate shielding material in small modular reactors (SMR). However, the preparation of large-sized, thick-walled lithium hydride blocks using conventional methods faces challenges such as slow ramp-up rates, excessive grain growth, and large temperature gradients, and microwave sintering technology may offer a good solution to the above problems. The material's dielectric spectrum properties and thermal conductivity parameters were evaluated using first principles calculations, which may serve as a reference for exploring the lithium hydride microwave sintering mechanism. The static dielectric constant of lithium hydride was 4.4 and the optical dielectric constant was 1. The thermal conductivity at 300 K was 15.88 (W m- 1 k-1), which was consistent with the existing experimental value of 14.7 (W m- 1 k-1). Furthermore, we discussed the effect of temperature and vacancy defects on the dielectric temperature spectral properties of the material. The results showed that while the thermal conductivity decreased with increasing temperature, and the phonon thermal conductivity of LiH (vacancy defects) decreased. The presence of a vacancy defect in LiH leads to an increase in the number of free electrons near the Fermi level, thereby enhancing its electron thermal conductivity. The optimal sintering frequency of LiH with vacancy defects also decreased.