The existing phases in arc-melted HfO2-RO1.5 samples (R = Gd, Y and Yb) were investigated by Raman spectroscopy and X-ray diffraction. The compositional regions of the monoclinic phase, metastable 72-and γ1-forms, were 0-6, 4-9 and 8-10 mol.% YO1.5 respectively, in the HfO2-YO1.5 system. A metastable tetragonal (t′) form is obtained at or below 12 mol.% RO1.5 compositions. The lattice parameters a and c of the t′-HfO2-RO1.5 solid solution increases and decreases with increasing RO1.5 content, and coincided with each other at 14 mol.% RO1.5 regardless of dopant species R. The lattice parameter of tetragonal HfO2-x mol.% RO1.5 with a fixed dopant concentration x increases with an increase of the ionic radius of dopant R3+ ion.The Raman band intensity at 450-500 cm-1, which is characteristic of the tetragonal phase, decreases with an increase of RO1.5 content and seems to disappear at an RO1.5 content of approximately 18-20 mol.%. It can be interpreted that the t″-form, which is a tetragonal phase with an axial ratio of unity, appears in the compositional region of 14-18 mol.% RO1.5.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics