Sinterização e caracterização mecânica e microestrutural de cerâmicas de SiC aditivadas com misturas de AIN/Dy2O3 e AIN/Yb2O3

Rodrigues

Santos

et al. 2010

MSF

Applications of stabilized zirconia include uses related to its low thermal conductivity, strength and electrical properties. Rare earth oxides (REO) were used as additives to stabilize appropriate crystalline phases at zirconia compacts. In this work zirconia based solid electrolytes were sintered with 10, 15 and 20 wt % of REO as sintering aids. Samples were prepared by uniaxial cold press and sintered at 1400 °C, followed by electric properties determination via impedance spectroscopy. Complimentary characterization was made by X-Ray diffractometry and quantitative phase analysis by Rietveld refinement. The ionic conductivity is affected by the amount of REO additive and this effect is correlated to the existing tetragonal and cubic phases for each composition

Effect of Rare Earth Addition on Electrical Properties of Zirconia Based Ceramics

Rodrigues

Santos

et al. 2010

MSF

Study of Polymorphs of Zirconia in the System ZrO2: ƞ wt% Re2O3 Obtained by Polymeric Precursor Method

Rodriguez²,

Silva

2012

MSF

In this paper we propose the stabilization of zirconium oxide with controlled additions of a rare earth elements concentrate, in the system ZrO2: ƞ wt% Re2O3 (withƞ=5.36, 10.47, 13.74, 16.91 e 20) whereRe2O3is a rare earth elements concentrate composed mainly of 76.88% of yttrium oxide, 12.1% of Dysprosium oxide, 4.04% of Erbium oxide and 1.94% of Holmium oxide. The synthesis method used was the Pechini method. The results show that additions of 5.36 and 20 wt% of the concentrate are enough to stabilize the tetragonal and cubic zirconia phases respectively, and that zirconium oxide polymorphs can coexist with additions within these limit. In the characterization of the obtained powders are presented and discussed the following results: differential scanning calorimetry, transmission electron microscopy and X-ray diffraction. Also, it was necessary to make analysis by Rietveld refinement because they had severe overlap in the diffraction peaks. One of the most relevant results is obtaining a raw material, cheap to be used in many technological applications.

Synthesis of ZrO2: ƞ wt% Re2O3 Powders by the Heterogeneous Coprecipitation Technique

Rodriguez²,

Silva

2012

MSF

The zirconia in its cubic phase (C-ZrO2) has gained scientific and technological interest because it has high ionic conductivity and is useful in applications where the transport of oxygen ions prevails, for example, in the oxygen sensors and solid oxide fuel cells [1,. In the pure zirconia, the Zr4+ ion is too small to sustain the fluorite structure at low temperatures, so it has to be partially replaced by a higher atomic radius cation and lower valence number, for example, the Y3 +, Mg2 +, Ca2 + and the rare earth cations TR3 +, [. Currently there are several synthesis methods used to obtain cubic zirconia, the most popular being the mixture of oxides and coprecipitation used industrially in the research labs, but these methods provide powders with different characteristics which will be decisive for a specific application. In this context, the objective of this study was the preparation of homogeneous mixtures of zirconia-rare earth in different concentrations in order to stabilize the C-ZrO2, using the technique of heterogeneous coprecipitation for potential applications in oxygen sensors.