Development of TiO2 white glazes for ceramic tiles☆

The thermal and microstructural behavior of a R2O–RO–(ZnO)–Al2O3–(TiO2)–SiO2 based macro-crystalline raw glaze system

“…Moreover, the white final color and suitable chemical composition of the porcelain bodies improve the crystalline formation and final appearance [6,7]. Besides the firing schedule and substrate composition, other factors such as glaze thickness and viscosity also affect the crystallization, resultant reflectance, and color of the porcelain glazes [8]. During sintering, the melted glaze diffuses into the pores by capillary forces and creates an interface layer.…”

“…The presence of TiO 2 has a favorable effect, and might act as a nucleating agent or an opacifier due to its amount in the glaze batch. Depending on the TiO 2 level, either individual crystals or a more overall matt crystalline effect occurs on the glaze surface [5,8]. The introduction of a nucleating agent in the glaze system enhances homogeneous crystal nucleation rates by increasing bulk free energy (ΔG), reducing crystal-liquid interfacial free energy (σ), or increasing the diffusion rate.…”

Structure property relations in multicomponent oxide systems with additions of TiO2 and ZrO2 for glaze applications

“…In the case of glazes with TiO 2 (anatase and rutile) the presence of rutile was observed, explained by the anataserutile transformation during the thermal treatment [9]. From a melt the high temperature stable phase always crystallizes, that is rutile here.…”

“…The shift of the main band maximum from 1100 cm 1 to lower frequencies may be related to a decreased degree of polymerization of the SiO 4 groups [30]. In terms of the effect of composition on the glaze properties it is known that ZrO 2 improves the wear rate of the glazes and TiO 2 decreases the glaze viscosity and improves acid resistance [9,31,32]. 29 Si MAS NMR results show that the glazes have a tetrahedral framework structure with a wide range of local coordinations Q 4 (0Al), Q 4 (1Al), Q 4 (2Al) and Q 4 (3Al) present producing broad spectral lines.…”

“…The high refractive indices for TiO 2 (rutile 2.76 and anatase 2.52) and ZrO 2 (2.20) compared to that of typical glaze materials (1.50-1.55) make them a good choice for potentially inducing opacity of glazes. TiO 2 addition to ceramic glazes also improves their acid resistance and decreases their viscosity [9]. Monoclinic zirconia (baddeleyite) might be used in complex ceramic glaze formulations as a nucleating agent, with the aim to promote zircon devitrification, which confers opacity and/or an improvement of mechanical properties [5].…”