Grain Boundary Segregation-Induced Phase Transformation in Yttria-Stabilized Tetragonal Zirconia Polycrystal

Abstract

ȬɋɐɲȪય‫ك‬ᓺᅀᇋɀɳȻɓȪএệᇋΧǽḩᨕіኝ◧Iᭀং ነ̡ӟ̘ɿগDŽЈ‫‬ɿগ⛡ᥴᗁɿ۱ᨀ⇠ೢଉ ɿ‫ڤ‬ғʶଉ ଉ ኇɅʀጋ‫ك‬༔‫⓯ݨ‬ƗȤࢫ746-8501 ୮‫ۑ‬᭔‫ٷܦ‬లϣ༔ᨊ 4560 ଉ ᴗ⒅შᗕ͆ᢼɿቦᄦᮾ᳣ᑿᐦቦᄦᮾ᳣ཀࢫ305-0047 ⇹᭔dzǞǿల٣ᥰ 1-2-1 ଉ ଉ ኇ̸গકগકрకકṾᮾ᳣ᲇἕ۰ᮾ᳣ᑿᐦࢫ113-8656 ኇ̸ȩᄙ̸ٚ೯᧯ 2-11-16The microstructure in 2.9 molಚ Y 2 O 3 -stabilized tetragonal zirconia polycrystal Y-TZP sintered at 1100c -1650c C was examined to clarify the role of Y 3ࢪ ions on the cubic-formation and grain growth processes. The cubic phase in Y-TZP stared to appear at 1300c C and the fraction of the cubic phase increased with the increasing sintering temperature. Scanning transmission electron microscopy and nanoprobe X-ray energy dispersive spectroscopy EDS measurements revealed that the Y 3ࢪ ion distribution in the grain interiors in Y-TZP was nearly homogeneous up to 1300c C and cubic phase regions in the grain interiors were formed clearly over 1300c C. The cubic phase region in the grain interior was extended as the sintering temperature increased. High-resolution electron microscopy and nanoprobe EDS measurements revealed that no amorphous layer existed along the grainboundary faces in Y-TZP, and Y 3ࢪ ions segregated at their grain boundaries over a width of ࣽ10 nm. The segregation peak of Y 3ࢪ ions was clearly seen at 1300c C, and above this temperature, Y 3ࢪ ions segregated at the grain boundaries not only between tetragonal grains but also between tetragonal and cubic grains. These results show that cubic phase regions started to be transformed from the grain boundaries andor the triple junctions in which Y 3ࢪ ions segregated. The cubic-formation mechanism in Y-TZP can be reasonably explained from the viewpoint of the Grain Boundary Segregation-Induced Phase Transformation model, and the grain-growth behavior is probably controlled by the solute drag effect of Y 3ࢪ ions segregating along the grain boundary.

Physical and mechanical properties of Ta2O5 doped zirconia-toughened alumina (ZTA) composites

“…The effect of sintering temperature on the composites bulk density is shown in Accordingly, the relative density of the studied bodies fired at 1650ºC increased with the increase in Ta [17]. Such defects promoted the diffusion rate and the jump frequency of Zr 4+ ions [18]. Ta 5+ ions will migrate by a vacancy diffusion mechanism [19].…”

Phase-transformation and grain-growth kinetics in yttria-stabilized tetragonal zirconia polycrystal doped with a small amount of alumina

“…[12][13][14] Therefore, 3 mol% Y-TZP specimens for grain-boundary energy measurement were prepared by the same pressing and sintering conditions as those described above, using the 3 mol% (5.2 mass%) Y-TZP powder without Al 2 O 3 and a 15 m 2 /g specific surface area (TZ-3Y grade, Tosoh, Tokyo, Japan). The specimens are termed 3Y.…”

“…[12][13][14] According to the phase diagram for the ZrO 2 -Y 2 O 3 system, the crystal phases in Y-TZP exit as the tetragonal-cubic (T-C) dual-phase at equilibrium temperatures above about 600 • C, and the mole fraction of cubic phase increases with increasing equilibrium temperature. 28 The segregation of Y 3+ ions in Y-TZP is caused by the driving force for T-C dual-phase partitioning.…”

Mechanical properties of zirconia toughened alumina with 10–24 vol.% 1Y-TZP reinforcement

“…This "solute drag" effect causes that tetragonal zirconia particles exhibit a stable shell and a transformable core. [22][23][24] In stabilizer coated powders this effect is even more pronounced. The beneficial coating concept has been successfully shown for TZP, ATZ and ZTA ceramics by the authors.…”