Phase quantification of mullite–zirconia and zircon commercial powders using PAC and XRD techniques

Abstract

The short range technique of the Perturbed Angular Correlation (PAC) and x-ray diffraction (Rietveld) methods have been employed to determine the phase content in commercial mullite-zirconia and zircon raw materials that are ordinarily used to produce ceramic materials. The PAC technique, which probes zirconiumcontaining compounds at nanoscopic level, showed that zircon contains crystalline ZrSiO 4 and an important amount of a structurally distorted zircon, which is also observed accompanying monoclinic zirconia in mullite-zirconia. This particular zircon phase was not detected by the long range x-ray diffraction-Rietveld technique. After an annealing treatment, important changes in crystalline contents of the powders allow confirming, by the x-ray diffraction-Rietveld method, the preexistence of this particular zircon phase. This fact must be taken into account when preparing multicomposites based on the present raw materials.

Structural Characterization of Natural and Processed Zircons with X-Rays and Nuclear Techniques

“…The decrease is higher for the SUD than for the USA and AUS zircon sands. The comparison of the values in Table 3 and Figure 4 shows that the most relevant hyperfine interaction ( 1 , 1 = 101 Mrad/s and 40 < 1 % < 49) corresponds to Zr lattice site in crystalline zircons in agreement with quadrupole frequency values reported previously [19,27]. With significant relative abundance (20 < 2 % < 35) very asymmetric and slightly distributed interaction 2 of quadrupole frequency ( 2 = 104-109 Mrad/s) similar to that of the crystalline zircon is also observed in the analyzed samples.…”

“…The above-mentioned interactions are accompanied by the interactions of similar or lower abundance 3 (11 < 3 % < 22) and 4 (8 < 4 % < 9). PAC studies on synthetic zircon and mullite-zirconia system [27] determined the presence of a similar 3 interaction associated with aperiodic regions. This interaction which exists in synthetic zircons cannot be attributed to the metamict state.…”

A short and long range study of mullite–zirconia–zircon composites

“…Mullite-zirconia-zircon multicomposites were prepared following reference [14] and using the commercial raw materials characterized by PAC in reference [4]. Mixtures of electrofused mullite-zirconia, named MZ, (MUZR, Elfusa LT, Brazil) powder milled to D 50 = 5 μm and 15, 25, 35 and 45 wt.% of zircon powder, named z, (Mahlwerke Kreuts, Mikron, Germany, D 50 = 2 μm) were consolidated by slip casting and dried at 110 • C. The resulting compacts, hereinafter labeled MZz15, MZz25, MZz35 and MZz45, were fired at 1,600 • C for 2 h at heating and cooling rates of 10 • C/min.…”

“…The existence of regions of aperiodic domains has been reported in some ceramic materials only when investigated by such short range techniques as perturbed angular correlations (PAC) [3,4] or extended X-ray absorption fine structure (EXAFS) [5]. The PAC method [6], in particular, has proved to be an efficient tool in the investigation of zirconia-based ceramics because it allows the determination of different atomic configurations around zirconium sites, hardly resolvable by other techniques.…”

“…The PAC technique has been recently applied to the study of mullite-zirconia and zircon raw materials [4]. It was found that both of them exhibited a novel hyperfine interaction describing non diffracting regions of zircon quite distinguishable from those depicting crystalline zircon [21], monoclinic zirconia and a distorted monoclinic zirconia already found in milled zirconias [22].…”