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Abstract

Micro-Raman spectra for PbZrxTi1—xO3 (PZT) with grain sizes of 60 and 40 nm have been obtained. The results show that the E(TO1) phonon mode of PbTiO3 (‘soft’ mode) displays a decrease in frequency and an increase in linewidth with increasing Zr concentration. A discontinuous behavior in the phonon energy for the soft mode occurs at a morphotropic phase boundary (MPB) of x ≈0.4 and 0.2 for grain sizes of 60 and 40 nm, respectively, and it can be attributed to a phase transition from ferroelectric tetragonal to ferroelectric rhombohedral phase. The nonzero soft mode frequency near the MPB results from a level repulsion between an additional phonon mode at ≈10 cm—1 and the soft mode. Raman enhanced behavior has been found for the lowest phonon mode with Zr contents in the range of 0.3 to 0.6. The dependence of Raman phonon modes for PbZr0.3Ti0.7O3 upon grain size has been analyzed and the results indicate a grain-size-induced phase transition at ≈13 nm.