ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Creep and conductivity were measured for polycrystalline α-Al2O3 doped with titanium or iron plus titanium. Both series of samples show a transition from acceptor domination to donor domination at the point where the concentrations of titanium and acceptors are approximately equal. Parameters in the expression for the creep rate $$\dot \varepsilon $$ ∞S nd-PPr O 2 exp (-QlkT) (whereS is the applied stress,d the grain size,Q an activation energy andn, p, r are constants characterizing the creep mechanism) indicate limitation by bulk diffusion in the acceptor-dominated samples and in the donor-dominated samples at low [Ti]. In the latter samples the ratelimiting species isO ″ i at highP O 2, VA ′″ Al at lowP O 2, with involvement of e′ at mediumP O 2. At higher titanium concentrations the creep rate is limited by generation/recombination of defects at grain boundaries. Iron appears to increase the rate of these grain-boundary reactions. When second-phase particles of Al2TiO5 are present, $$\dot \varepsilon $$ is decreased but ionic conductivity is increased.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01082112
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