Structure of Alumina and Zirconia Nanoparticles Synthesized by the Karlsruhe Microwave Plasma Process

Abstract

Applying the Karlsruhe Microwave Plasma Process, alumina and zirconia particles with particle sizes in the range from 2 to 5 nm were synthesized. Additionally, the influence of small amounts of iron(III)-oxide, chromia, and magnesia on the crystallization and phase transitions in alumina powders was investigated. It is shown that these dopants may influence the crystallization behavior significantly. Especially, the addition of 1 mol% iron(III)-oxide reduced the temperature of the formation of a-alumina from 1200 °C to 300 °C.

Effect of iron doping on the properties of nanopowders and coatings on the basis of Al2O3 produced by pulsed electron beam evaporation

“…In contrast to the results [17], the multiphase nanocrystalline powders containing α and γ phases of Al 2 O 3 and a series of other unidentified phases were obtained in our case during the deposition of NPs on the cold glass substrate. No amorphous phase was found in NPs using XRD.…”

“…It is known that there is a large number of works on the preparation of amorphous and amorphous nanoc rystalline (A NC) films [7,8], coatings [9,10], and submicron and NPs (NPs) [11,12] on the basis of Al 2 O 3 using different high temperature methods: pulsed laser evaporation [13,14], continuous and pulsed elec tron evaporation [15,16], different modifications of magnetron sputtering [9,10], plasma chemical technol ogies [17,18], detonation synthesis [19,20], etc.…”

“…On the one hand, the introduction of different dopants into Al 2 O 3 makes it possible to control the crystallization temperature of the amorphous phase [25]; on the other hand, iron doping may lead to unex pected phase transformations during further anneal ing, e.g., amorphous phase → α phase Al 2 O 3 [17]. In [17], amorphous NP Al 2 O 3 doped with 0.1 mole Fe was obtained using the plasma chemical method, which was transformed into the stable α phase of Al 2 O 3 at a record low temperature of 143°C after annealing in air.…”

“…In [17], amorphous NP Al 2 O 3 doped with 0.1 mole Fe was obtained using the plasma chemical method, which was transformed into the stable α phase of Al 2 O 3 at a record low temperature of 143°C after annealing in air. The typical transformation of the amorphous phase into the γ phase of Al 2 O 3 was observed with the increase in the iron concentration of up to 0.6 mole.…”

“…The plasma chemical method [17] and evapora tion by means of pulsed electron beam (PEB) make it possible to produce nanoparticles (NPs) of a similar size (2-8 nm); therefore, it was interesting to repro duce the achievements of [17] by means of the electron evaporation and to simultaneously study the effect of iron on the different characteristics of the Al 2 O 3 Fe 2 O 3 samples at a low doping level, which is studied insufficiently.…”