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Yttria Doping and Sintering of Submicrometer‐Grained α‐Alumina
Author(s) -
Sato Eiichi,
Carry Claude
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb08950.x
Subject(s) - yttrium , yttria stabilized zirconia , materials science , sintering , doping , activation energy , grain size , grain boundary , saturation (graph theory) , precipitation , composite material , metallurgy , mineralogy , microstructure , cubic zirconia , ceramic , chemistry , optoelectronics , mathematics , physics , combinatorics , meteorology , oxide
The sintering behavior of α‐alumina powders doped with magnesia (500 or 1500 ppm) and yttria (0, 500, or 1500 ppm) was investigated using constant‐heating‐rate dilato‐metric experiments. The apparent activation energies for the intermediate stage of sintering were 740, 800, and 870 kJ/mol for 0, 500, and 1500 ppm yttria doping levels, respectively; these were independent of magnesia doping. Yttria‐doped powder compacts exhibited systematic anomalous second peaks in the densification rate curves at certain grain sizes which were determined only by yttria doping levels. Before the anomalous peak, with lower yttrium contents at grain boundaries, yttrium in an atomic state delays densification and raises the apparent activation energy. Beyond the peak, with higher yttrium contents at grain boundaries, yttria‐rich precipitation delays the densification. Within the peak, yttrium segregation near the saturation level enhances densification.