Synthesis and characterization of LiZnP and LiZnAs semiconductor material

Research for a reliable solid-state semiconductor neutron detector continues because such a device has not been developed, and would have greater efficiency, than present-day gas-filled 3He and 10BF3 neutron detectors. Further, a semiconductor neutron detector would be more compact and rugged than most gas-filled or scintillator neutron detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78 MeV, a larger yield than the 10B(n,α)7Li, and is easily identified above background radiation interactions. Hence, devices composed of either natural Li (naturally 7.5% 6Li) or enriched 6Li (approximately 95% 6Li) may provide a semiconductor material for compact high-efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, known as Nowotny-Juza compounds (AIBIICV), are desirable for their cubic crystal structure and semiconducting electrical properties. These compounds were originally studied for photonic applications. In the present work, Equimolar portions of Li, Zn, and P or As were sealed under vacuum (10−6 Torr) in quartz ampoules with a boron nitride lining, and loaded into a compounding furnace. The ampoule was heated to 200 °C to form the Li-Zn alloy, subsequently heated to 560 °C to form the ternary compound, LiZnP or LiZnAs, and finally annealed to promote crystallization. The chemical composition of the synthesized starting material was confirmed at Galbraith Laboratories, Inc. by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), which showed the compounds can be reacted in equal ratios, 1-1-1, to form ternary compounds. Recent additions to the procedure have produced higher yields, and greater synthesis reliability. Synthesized powders were also characterized by x-ray diffraction, where lattice constants of 5.751±.001 Å and 5.939±.002 Å for LiZnP and LiZnAs, respectively, were determined.