Compositional homogeneity of ferroelectric (Pb,La)(Ti,Zr)O3thick films

Abstract

Quantified wavelength dispersive spectroscopy (WDS) x-ray element maps were used to characterize active (Pb,La)(Ti,Zr)O3(PLZT) layers on Pt/PLZT/Al2O3substrates, one fired at 1050 °C and the other at 1150 °C. In the layer fired at 1050 °C, randomly distributed micrometer-sized compositional irregularities were observed as La-rich regions that were in most cases enriched also with Ti and deficient in Pb and Zr compared to the matrix. Such compositional imperfections were not observed in the PLZT layer fired for the same duration at 1150 °C. The level of microheterogeneity for all elements in the specimen fired at 1150 °C and for Pb, Ti, and Zr in the specimen fired at 1050 °C was below 1% relative at confidence level of 99% while for La it was as much as 2.5% relative. In point-beam line profiles across the active layer starting from the Pt electrode toward the outer surface of the cross-section of the PLZT film, the Pb concentration decreased continuously in both samples, confirming the importance of providing a properly equilibrated partial pressure of Pb around the sample during the entire firing process. Better dielectric and ferroelectric characteristics of the specimen fired at 1150 °C compared to the sample fired at 1050 °C were attributed to the differences in compositional heterogeneity between these samples. The study of the micro-compositional characteristics of these ceramic materials with quantitative WDS mapping has contributed to the optimization of processing parameters and hence to the understanding of the properties of ferroelectric PLZT materials.