High‐purity zirconium diboride (ZrB2) powders with submicrometer particle size were synthesized by borothermal reduction of nanometric ZrO2 powders in vacuum. The reaction process was experimentally and thermodynamically assessed. B2O3 was identified as a possible intermediate reaction product. ZrO2 completely converted to ZrB2 when thermally treated at 1000°C for 2 h in a vacuum, but the removal of residual boron‐related species required a temperature above 1500°C. ZrB2 powders obtained at 1000°–1200°C showed a faceted morphology, whereas those prepared above 1500°C had a nearly spherical morphology. The particle size that was calculated from the measured surface area increased with the increasing synthesis temperature from 0.15 μm at 1000°C to 0.66 μm at 1650°C. The oxygen content of the ZrB2 powders synthesized at 1650°C was as low as 0.43 wt%.

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The composite Ag 3 PO 4 /CeO 2 photocatlyst, a novel p-n type heterojunction, has been successfully fabricated through a facile hydrothermal process combined with a successive in situ precipitation technique. The X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV-visible diffuse reflectance spectra (DRS) were used to characterize the as-obtained products. The SEM and TEM image show that CeO 2 particles have been successfully loaded and well distributed in the surface of Ag 3 PO 4. The photocatalytic activities of the p-Ag 3 PO 4 /n-CeO 2 heterojunctions were investigated for their efficiency on the degradation of Rhodamine B (RhB) under ultraviolet light and visible light irradiation, and the results showed that the p-Ag 3 PO 4 /n-CeO 2 heterojunctions possessed remarkable photocatalytic activities. The enhanced photocatalytic activity can be attributed to the extended absorption in the visible light region resulting from the Ag 3 PO 4 and the effective separation of photogenerated carriers driven by the internal electrostatic field in the junction region.

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