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Diffusion of 110m Ag Tracer in Polycrystalline and Single‐Crystal Lead‐Containing Piezoelectric Ceramics
Author(s) -
Lewis Daniel J.,
Gupta Devendra,
Notis Michael R.,
Imanaka Yoshihiko
Publication year - 2001
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.1151-2916.2001.tb00914.x
Subject(s) - crystallite , activation energy , materials science , grain boundary diffusion coefficient , grain boundary , ceramic , diffusion , analytical chemistry (journal) , single crystal , crystallography , effective diffusion coefficient , enthalpy , condensed matter physics , mineralogy , chemistry , thermodynamics , microstructure , metallurgy , physics , medicine , chromatography , radiology , magnetic resonance imaging
We have conducted diffusion measurements of radioactive 110m Ag tracer in single‐crystal PbMgNbO 3 –PbTiO 3 (PMN‐PT) and in polycrystalline 50Pb(Ni 1/3 Nb 2/3 )O 3 ·35PbTiO 3 ·15PbZrO 3 (PNN‐PT‐PZ) piezoelectric ceramics. Both materials measured belong to the perovskite family. Diffusion in PMN‐PT is characterized by an activation energy of 277 kJ/mol and pre‐exponential factor of 0.0034 m 2 /s and compares well with cation diffusion in high‐temperature superconducting YBa 2 Cu 3 O 7–δ . Diffusion in polycrystalline PNN‐PT‐PZ, on the other hand, is many orders of magnitude faster and is attributed to grain boundaries. PNN‐PT‐PZ has a lower activation energy, 168 kJ/mol, and a combined pre‐exponential factor ( s δ( D b ) o , where s is the segregation factor of silver, δ the thickness, and ( D b ) o the pre‐exponential factor for grain boundaries) of 3.7 × 10 −9 m 3 /s. The unusually large combined pre‐exponential factor infers large segregation of silver at the grain boundaries and small solid solubility within the grains. It is possible, using a semiempirical model, to compute metal– (silver–) ceramic interface energies as a function of temperature, from which values of 90 kJ/mol and 0.9 R are obtained for enthalpy and entropy, respectively, for grain‐boundary segregation.