A method based on a hydrothermal process was applied to obtain not only ultrafine but also well-dispersed CeO₂ nanoparticles by the application of citric acid as a protective agent against particle growth. The well-defined crystallites have a narrow size distribution, and the mean size and BET specific surface area are 3.1 nm and 211 m² g⁻¹, respectively. A mixture of the condensation product of boric acid and 2,2′-iminodiethanol (diethanolamine) and cerium oxide nanoparticles has been found to yield turbostratic boron nitride (tBN) coatings on the cerium oxide surface after heating the mixture in a flow of ammonia. Formation of a tBN layer was identified using high-resolution electron microscopy and infrared and X-ray photoelectron spectroscopies. The surface tBN layer was found to be a few nanometres thick with a surface coverage of 51.2%. However, coating of cerium oxide with such a tBN layer is suitable both for whitening the colour whilst maintaining good ultraviolet absorption properties and for restraining the high oxidation activity of cerium oxide.

A novel Pt/CeO₂–ZrO₂–Bi₂O₃ catalyst was prepared to realize complete CO oxidation at room temperature or below even in the presence of moisture. Using this catalyst, a high CO oxidation activity and a high stability against moisture have been realized simultaneously.

Novel inorganic yellow pigments, Bi_{1−x−y−z}Ca_xZn_yLa_zVO_4−(x+y)/2 (0.04 ≤ x ≤ 0.12; 0.01 ≤ y ≤ 0.05; 0.01 ≤ z ≤ 0.10) were synthesized as environmentally friendly inorganic materials, and their color properties were characterized. All the pigments exhibited brilliant yellow colors, and using the CIE L*a*b* system, the most vivid yellow hue was obtained for Bi_0.85Ca_0.08Zn_0.02La_0.05VO_3.950 with a yellowness value (b*) of +93.5, which is much greater than that of a commercially available BiVO₄ pigment (b* = +76.9). Since BiVO₄ is an environmentally friendly inorganic yellow pigment, and Ca, Zn, and La are also nontoxic and safe elements, the Bi_0.85Ca_0.08Zn_0.02La_0.05VO_3.950 pigment could be an effective alternative to conventional toxic yellow pigments.