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-sca ttering spectroscopy, and the results were compared with those of x-ra y-diffractometry investigations. The unfired films were subjected to r apid firing in an air atmosphere at temperatures ranging from 960 to 1 150-degrees-C. During firing the composition of the films changed grad ually 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. Corres pondingly, the Raman spectra also changed with increasing firing tempe rature. The variation in Raman spectra was characterized by three freq uency regions, denoted as the low-, intermediate-, and high-frequency region, respectively, which are related to three cubic T1u modes. More over, 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'' i n structure.