title: Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2Glass: Growth of an Oriented β-Y2Si2O7Layer and Epitaxial ZrO2.
abstract: The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7(YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2(Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2and ε-YS is proven and multiple twinning relationships occur in the YS phases.
authors.affiliation: Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, Jena 07743, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wisniewski
authors.affiliation: Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, Jena 07743, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Seidel
authors.affiliation: Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Walter-Huelse-Straße 1, Halle (Saale) 06120, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Patzig
authors.affiliation: Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, Jena 07743, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rüssel