Raman spectroscopy has been used to study the ferroelectric tetragonal to paraelectric cubic phase transition Tc in undoped BaTiO3 (BT) and (Ba0.92A0.08)TiO3 [where A=Ca (BCT), Sr (BST), and Pb (BPT)]. In BT and BPT, mode characteristic of the tetragonal phase at 303 and 710cm−1 persisted until >50°C above Tc, indicating the presence of local dynamic polar clusters well above the displacive phase transitions, ∼120 and ∼149°C, respectively. However, in BCT and BST, the Raman spectra exhibited only broad second order bands above Tc, suggesting that Ca and Sr, A-site dopants supress local dynamic polar clusters.
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Pasha et al. (2007) studied this question.
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