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Abstract. Titania nanopowders obtained by hydrolysis of titanium alkoxides and consecutive hydrothermal treatment were compacted and sintered. The influence of preparation conditions (alkyl, pH of hydrolysis, temperature of hydrothermal treatment, compacting pressure, sintering temperature) on the porosity of powders, compacts and sintered bodies was investigated by nitrogen sorption and mercury intrusion. Optimum conditions are derived to prepare high-density ceramics at relatively low sintering temperature.Key words: titania, hydrothermal synthesis, pore volume distribution, density, compacting pressure.For industrial applications titania ceramics should be of high, homogeneous density [1]. This can be achieved at moderate sintering temperatures starting from appropiate powders.The hydrothermal treatment [21 is a suitable method to obtain titania powders with optimal properties concerning the production of ceramics for electronic components. But the properties of the titania powder and, consequently, of the compacts and ceramics depend on the physical and chemical conditions of the synthesis [3] e.g. pH, temperature during the precipitation, concentrations, dropspeed, freeze drying [4]. A controlled hydrolysis is important to get extreme small particles (submicron, nanopowders) and a close particle size distribution [5].The building of the structure of sintered ceramic compacts depends upon the properties of the primary powders used. Conventionally the green density of the used shapes seemed to be most important, but new results emphasize the significance of the influence of the * Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday ** To whom correspondence should be addressed arrangement of the initial nanopowder particles and the pore volume distribution in the green body. The pore volume distribution is an essential factor strongly influenced by the presence or absence of agglomerates.Variation in the processing parameters delivers in some cases powders with nearly the same properties concerning particle size distribution and surface area, but after compacting at identical pressure and identical sintering temperature, some have densities about 90 %, other 99% and more. The differences can be predicted by viewing the porosity of the green bodies and described with the characteristics of the porosity and the pore size distribution of the sintered pellets and shapes, respectively.The development of the porosity of titania shapes synthesized hydrothermally from titanium alkoxides was examined with regard to the dependence on pH and the temperature during synthesis, the compacting pressure of the green bodies, and the temperature at the sintering process. ExperimentalA solution of 0.15 mol titanium tetra-ethoxide in 11 ethanol was added gradually within 1 h to a boiling solution of 0.5 mol urea and 1.5mol demineralized water in 11 ethanol. Before mixing, the solutions were ultrafiltrated to exclude seeding particles. A precipitation occurs during the addition. Due to...