As important materials in modulating the polarization of light, birefringent crystals have attracted considerable attention and played crucial roles in the field of optical communication and the laser industry. Limited by the transparency range, few birefringent crystals can be used in the deep-ultraviolet (DUV) region, except for α-BaBO (α-BBO). However, the application of α-BBO in the DUV range is restricted by the relatively high cutoff edge and low transmittance rate below 200 nm. In this paper, we design and synthesize a new fluoroborate, NaBOF, by introducing fluorine into borate system. It possesses a short cutoff edge of 169 nm and birefringence larger than 0.080 at 589.3 nm. The NaBOF crystals with sizes up to 3.0 mm × 1.5 mm × 0.2 mm have been grown with good quality by a high-temperature solution method in the open system. First-principles calculations were carried out to understand the optical properties.

Human exploration of the Moon is associated with substantial risks to astronauts from space radiation. On the surface of the Moon, this consists of the chronic exposure to galactic cosmic rays and sporadic solar particle events. The interaction of this radiation field with the lunar soil leads to a third component that consists of neutral particles, i.e., neutrons and gamma radiation. The Lunar Lander Neutrons and Dosimetry experiment aboard China’s Chang’E 4 lander has made the first ever measurements of the radiation exposure to both charged and neutral particles on the lunar surface. We measured an average total absorbed dose rate in silicon of 13.2 ± 1 μGy/hour and a neutral particle dose rate of 3.1 ± 0.5 μGy/hour.