Study of the Local Structure Changes in PbTiO 3 by Pb L III EXAFS

The Pb L III -edge EXAFS for PbTiO 3 was measured in the temperature range from 20 K to 873 K. The structural changes in Pb-O and Pb-Ti atomic pairs through the critical temperature (763 K) due to the phase transition from tetragonal to cubic phase were discussed from the local point of view. Three types of atomic pairs, shorter Pb-O(1), medium Pb-O(2) and longer Pb-O(3) were analyzed independently. The former two Pb-O pairs show the "order-disorder" type phase transition; Pb-O distance does not change through T c . On the other hand the last one shows the "displacive" type; the interatomic distance decreases discontinuously at T c and the mean square relative displacement shows the soft mode behavior.

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