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Decorated Dislocations in Magnesia Crystals
Author(s) -
PULLIAM GEORGE R.
Publication year - 1963
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.1151-2916.1963.tb19772.x
Subject(s) - spinel , dislocation , materials science , vacancy defect , crystallography , ion , magnesium , lattice (music) , condensed matter physics , mineralogy , metallurgy , chemistry , composite material , organic chemistry , physics , acoustics
Diffusion of iron ions into magnesia single crystals at 1350° C in a moist atmosphere produces a host lattice of magnesiowüstite. Spinel dissolved in the lattice at this temperature precipitates on dislocations during cooling. The precipitates are large enough to be viewed with a transmission microscope. Reheat treatment of the crystals containing decorated dislocations in atmospheres of CO 2 ‐H 2 results in rather gross dendritic voids through the reduction of the ferric ion. Chemically induced vacancies were found to result in the formation of helical and prismatic loop dislocation arrangements typical of vacancy condensation mechanisms. The spacing of rows of prismatic loops was found to be in agreement with the values predicted by the equations of Bullough and Newman if one assumes a critical shear value of 5(10) −6 μ for magnesiowüstite at 1350°C.