PHASE-TRANSITION REVEALED BY RAMAN-SPECTROSCOPY IN SCREEN-PRINTED LEAD-ZIRCONATE-TITANATE THICK-FILMS

The transition from rhombohedral phase to tetragonal in screen-printed lead zirconate titanate (PZT) thick films was studied using Raman-scattering spectroscopy, and the results were compared with those of x-ray-diffractometry investigations. The unfired films were subjected to rapid firing in an air atmosphere at temperatures ranging from 960 to 1150-degrees-C. During firing the composition of the films changed gradually as lead evaporated, which moved the composition of films to the ZrO2-PZT region and resulted in precipitation of ZrO2. This caused the original rhombohedral structure to be converted to tetragonal. Correspondingly, the Raman spectra also changed with increasing firing temperature. The variation in Raman spectra was characterized by three frequency regions, denoted as the low-, intermediate-, and high-frequency region, respectively, which are related to three cubic T1u modes. Moreover, it was also observed that the appearance of tetragonal modes was delayed from the formation of tetragonal structure during the process. This discrepancy suggested the existence of a certain ''mismatch'' in structure.