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A facile route for the preparation of WO 3 • 0.33H 2 O hexagonal-shaped nanodiscs composed of nanosheets via hydrothermal treatment of an aqueous peroxo-polytungstic acid solution has been demonstrated for the first time. The hexagonalshaped nanodiscs obtained have an average diameter of 200 nm and a mean thickness of several tens of nanometers. The effects of the preparation conditions such as the hydrothermal temperature and precursor concentration on the crystalline phase and morphology of the products have been studied systematically. The WO 3 • 0.33H 2 O nanodiscs with an orthorhombic structure and regular hexagonal morphology can be synthesized in a wide hydrothermal temperature range from 100 to 200 °C. However, in the absence of hydrogen peroxide, monoclinic tungsten oxide square nanoplates are obtained. The hexagonal-shaped nanodiscs morphology have been well explained based on the crystal structure of orthorhombic WO 3 • 0.33H 2 O. It is expected that this material with a well-defined and accessible crystal surface may find applications in catalysis, gas sensors, and other research areas.

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The boron phosphide (BP) semiconductor has many remarkable features, including high thermal neutron capture cross section of the 10 B isotope, making it attractive for neutron detection applications. Effective and efficient neutron detection require BP to also have high crystal quality with optimum electrical properties. Here, we present the heteroepitaxial growth of high quality BP films on a superior aluminum nitride(0001)/sapphire substrate by chemical vapor deposition. The effect of process variables on crystalline and morphological properties of BP was examined in detail. BP deposited at high temperatures and high reactant flow rate ratios produced films with increased grain size and improved crystalline orientation. Narrower full width at half-maximum values of BP Raman peaks (6.1 cm −1 ) and ω rocking curves (352 arcsec) compared to values in the literature confirm the high crystalline quality of produced films. The films were n-type with the highest electron mobility of 37.8 cm 2 /V·s and lowest carrier concentration of 3.15 × 10 18 cm −3 . Rotational twinning in BP due to degenerate epitaxy caused by 3-fold BP(111) on 6-fold AlN(0001) was confirmed by synchrotron white beam X-ray topography. This preliminary study showed that AlN is an excellent substrate for growing high quality BP epitaxial films with promising potential for further enhancement of BP properties.