A variety of titanate gels were prepared from lead acetate and titanium isopropoxide in methoxyethanol. In the present study, 'H and 13C Fourier transform-nuclear magnetic resonance and mass spectroscopic techniques were used to identify the structure of the lead and titanium precursors formed from lead acetate and titanium isopropoxide, respectively, when refluxed in methoxyethanol. The lead and titanium precursors were determined to be Pb(OOCCH3) (OC2H40CH3) -xH20, where x < 0.5, and T~Z ( O C~H~O C H~)~, respectively. Similar spectroscopic procedures were applied to identify the lead titanium complex formed from the reaction between lead and titanium precursors. [

Zr02 powder was prepared by a sol-emulsion-gel method at temperatures below 140°C from ZrO(N03)2 * nH20. The asprepared powder was amorphous, but crystallized into the tetragonal structure by 600°C. The metastable tetragonal powder (600°C) was comprised of ultrafine 4-to 6-nm size particles. On heat treatment, the tetragonal form completely transformed into the monoclinic state at 1100°C. Preliminary studies indicate good sinterability with densities greater than 94% at 1100°C and with a grain size of 0.25 pm.[Key words: zirconia, sol-gel, emulsion, heat treatment, particles.] I. Introducation ARTICLE size, shape, and distribution are important fac-P tors for the densification of ceramic powders. Ultrafine powders containing submicrometer particles lead to lower sintering temperatures and finer grain size distributions. Improved properties result from the small grain sizes and high interfacial surface Nanosized particles can further increase sinterability at lower temperatures with smaller residual pores and grain sizes? Rapid diffusivities and enhanced solubilities in nanosized ceramics arise from the higher fraction of atoms in the grain-boundary regions. The majority of atoms are at or near the surface, and surface properties dominate. Recently, considerable effort has been expended in developing low-temperature routes for the chemical synthesis of ultrafine ceramic powders: Roy: Bowen: Mazdiyasni? and co-workers reported on the sol-gel processing8 of ultrafine ceramic powders derived from their corresponding metal alkoxides. In some cases, the fine particles were found to be agglomerated, which resulted in longer sintering times and higher sintering temperatures. To overcome this problem, Bowen and co-workers' used emulsion methods for the preparation of ultrafine, unagglomerated, soft powders.Another important aspect of powder preparation is the cost effectiveness of the method used. Most of the above studies used metal alkoxides as precursors, which can be somewhat expensive for the large-scale preparation of ceramic powders. In the present study, zirconyl nitrate, ZrO(N03)2. nHzO, a relatively inexpensive precursor, was used for the preparation of Z r O z powder. Z r O ( N 0 3 ) 2 . n H 2 0 was chosen over ZrOC12. nH20, since nitrogen-containing compounds lead to cleaner and easier burnout compared with chloride-containing compounds.In the present work, a combination of sol-gel and emulsion'" methods was used for the preparation of Z r 0 2 powders. In the sol-emulsion-gel method, water droplets containing zirconium ions are suspended and stabilized in an organic nonpolar solvent by addition of an appropriate surfactant. P. Morgan-contributing editoiThe emulsion droplets are gelled by ammonia gas, and the gel droplets are then stabilized by removing water during heterogeneous di~tillation.'~'~ The choice of the surfactant to be used in an emulsion is determined by the compatibility of the surfactant's hydrophobic-lipophilic balance (HLB) number '' and the composition of the suspension. In the present study,...

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