Vaporization of Lead Zirconate-Lead Titanate Materials |
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Authors: | DAVID A. NORTHROP |
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Affiliation: | Sandia Laboratory, Albuquerque, New Mexico 87115 |
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Abstract: | A thermogravimetric investigation of the vaporization of cold-pressed Pb(Zr0.65Ti0.35)O3 in vacuum from 690° to 1130°C shows that the vaporization occurs in two steps. An initial loss of 1 to 7 wt% proceeds by a mechanism with a logarithmic time dependence and represents the vaporization of the unreacted PbO that remains after the initial calcining. The second step proceeds by a slower, diffusion-controlled mechanism with a parabolic time dependence. It is shown that this rate-determining step is bulk diffusion across a thickening lead-depleted layer in the cold-pressed pellet, despite pore volumes of 24 to 42%. The rate constant, g/cm2 sec½, for the parabolic weight loss process is expressed by: log K = (3.37 ± 0.14) - (8.46 ± 0.16) (103/ T K). The activation energy is 38.7 ± 2.0 kcal/mole. |
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