Zinc oxide, which has photocatalytic activity, is used as a white pigment for cosmetics, resulting in a certain amount of sebum on the skin to be decomposed by the ultraviolet radiation in the sunlight. In this work, zinc phosphates as novel white pigments for use in cosmetics were prepared from zinc nitrate and sodium dihydrogen phosphate, and then ball-milled under various conditions. The chemical composition, powder properties, photocatalytic activity, color phase, moisture retention, and smoothness of the zinc phosphates were studied. The zinc phosphate particle size was decreased by mechanical treatment. In particular, the sample treated with sodium lactate solution had much smaller particles. The milled zinc phosphates exhibited less photocatalytic activity than zinc oxide, and thus should not decompose sebum on the skin. The milled zinc phosphates showed sufficiently high reflectance within the range of visible light to act as novel white pigments. The sample treated with sodium lactate solution had higher water retention than the sample treated with water. Further, the slip resistance and roughness of the powder particles decreased as a result of treatment with sodium lactate solution.

Titanium dioxide is a photocatalytically active substance used as a white pigment for cosmetics. In sunlight, titanium dioxide catalyzes decomposition of a certain amount of sebum on the skin by ultraviolet radiation. Herein, a novel white pigment for use in cosmetics was developed from titanium dioxide and phosphoric acid at pH = 4 with and without glycerin, sodium lactate, lactic acid, and urea. The chemical composition, powder properties, photocatalytic activity, color phase, and smoothness of the samples were studied. Addition of glycerin led to a decline in the intensity of the X-ray diffraction (XRD) peak of TiO₂ relative to that of the other samples. The particle size of the materials prepared with and without additives was 0.3 μm; however, extensive aggregation was observed in the obtained materials. The photocatalytic activity of TiO₂ was inhibited by phosphoric acid treatment. The materials prepared with sodium lactate, lactic acid, and glycerin exhibited higher photocatalytic activity than that prepared without additives. The obtained materials showed a high reflectance in the range of visible light, and the L^* values in L^*a^*b^* color space were high (where L^* defines lightness, a^* denotes the red/green value, and b^* the yellow/blue value). These results indicate that the samples prepared in this work are suitable for use as white pigments.

Titanium phosphates were prepared from titanium chloride and sodium pyrophosphate at various pH in hydrothermal process as a novel white pigment for cosmetics. Their chemical composition, powder properties, photo catalytic activity, colour phase and smoothness were studied. The obtained materials had a higher Ti/P ratio than that used in preparation conditions because of the formation of titanium oxide and hydroxide. The samples prepared at pH = 4 had particles smaller than 100 µm. Titanium phosphates had less photo catalytic activity to protect the sebum on the skin. The obtained materials in hydrothermal process and their thermal products at 100 ℃ showed high reflectance in the range of visible light.

Titanium oxide that has photocatalytic activity is used as white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, as novel white pigment, titanium phosphates were synthesized with titanium sulfate and phosphoric acid for cosmetics. Their chemical composition, powder properties, photocatalytic activity, color phase, moisture retention, and smoothness were studied. These titanium phosphates had less photocatalytic activity to protect the sebum on the skin. Samples without heating and those heated at 100 ℃ showed high reflectance in the range of visible light. Sample prepared in Ti/P = 3/2 had higher moisture retention than samples prepared in other Ti/P ratios.

Bulk samples of lanthanum polyphosphate were synthesized through a hydrothermal hot-pressing (HHP) process. In this process, pressing temperature, pressure and volume of water were varied in order to improve the density and strength of the resulting materials. The strength of the bulk samples was estimated through drilling and ultrasonic treatments. In order to improve the strength of the materials, the use of microwave irradiation was examined. Lanthanum polyphosphate formed porous bulk samples with a filling factor of approximately 70%, which was calculated from real and theoretical densities. With respect to machinable strength, a drilled hole greater than 7.0 mm in diameter was obtained on some bulk samples, and the diameter of the samples was 14 mm. The HHP process is a useful method for obtaining bulk samples of lanthanum polyphosphate. Bulk lanthanum polyphosphate containing water crumbled easily to a powder form upon ultrasonication. However, these bulk samples retained their shape upon ultrasonication, despite containing water, after exposure to microwave irradiation, and also experienced minimal weight loss. Furthermore, to study the effect of microwave heating, bulk lanthanum orthophosphate, yttrium orthophosphate and polyphosphate were also examined.

The effects of cerium substitution, use of additives, and heating temperature on the chemical composition and catalytic activity of iron phosphate were evaluated. Iron–cerium phosphate was prepared from iron nitrate, ammonium cerium nitrate, and sodium phosphate in ethylene glycol using sodium dodecyl-sulfate or acetylacetone as additive. The chemical composition, particle shape and size distribution of the obtained samples were respectively evaluated based on ICP and XRD, SEM, and laser diffraction/scattering analysis. The catalytic activity was evaluated based on the decomposition of the complex formed from formaldehyde, ammonium acetate, and acetylacetone. XRD peaks corresponding to FePO₄ were observed for the samples heated at 600 ℃ whereas samples treated at lower temperatures were amorphous. Iron–cerium phosphates heated at 200 ℃ and 400 ℃ exhibited high catalytic activity for the decomposition of the aforementioned complex.