**4. Sintering of TCO materials**

596 Sintering of Ceramics – New Emerging Techniques

1380 °C for theree hours. Colouration from yellow to green and XRD peaks of indium-tin-

An alternative ITO synthesis process is given in (Stenger, et al., 1999). Here molten metallic indium tin alloy has been reacted with oxygen in a plasma arc furnace. The product is subsequently quenched by a gas stream at cooling rates between 105 K/s to 108 K/s to a final temperature between +50 °C and +400 °C. Thereby mixed indium tin oxide powders were produced with specific surface area of 3 m2/g at maximum. As the powder tends to formation of large agglomerates the size of different ramifications has been analysed by electron microscopy and documented as primary particle size being in the range of 0.03 µm up to 1.0 µm. Hot melt spraying of indium tin melts in oxydizing atmospheres and subsequent quenching is also suitable to process indium tin oxide powders. The agglomerated particle are porous and reveal particle sizes up to 170 µm (see Figure 4).

Compared to this the commercial powder ZY-ITO (Dow Chemical Co. Ltd.) is composed of a mixture of 90 wt.-% In2O3 and 10 wt.-% SnO2, with a specific surface area of 32.0 m2/g and

Although various studies of synthesis, characterization and application of Al:ZnO thin layer systems are given in the literature (Stanciu, et al., 2001, Selmi, et al., 2008), there are only a few investigations referring to synthesis and processing of nanosized Al:ZnO particles. Flame spray pyrolysis of liquid Al- ad Zn precursors led to uncontrolled Al:ZnO stoichiometries and segregations of the spinel and wurzite phase combined with evaporation of the metallic Zn phase (Kim, 2008). Vapour condensation (Strachowski, et al., 2007) and spray pyrolysis (Hsiao, et al., 2007) as well as low-pressure spray pyrolysis (Hidayat, et al., 2008) resulted in highly agglomerated particles exhibiting poor redispersing

Fig. 7. Indium tin oxide powder produced by hot melt spraying and subsequent quenching:

The processing of suitable AZO particles for optoelectronic applications is therefore still challenging. Several alternative processing routes have been elaborated with limited

Pore volume of the powder as a function of particle size.

a mean primary particle size in the range of 3.4 µm.

**3.2 AZO powder synthesis** 

characteristics.

oxide without exception proved the complete transforma-tion to indium tin oxide.
