Three Layer Perovskite-Like Structured Pr3Ti2TaO11 Ferroelectrics with Super-High Curie Point

Pr3Ti2TaO11 was prepared by co-precipitation and subsequent solid-state reaction at 1300 degrees C. The compound has a perovskite-like layered structure belonging to space group Pmc2(1) with unit cell parameters a=3.8689(3)angstrom, b=20.389(2)angstrom, c=5.5046(5)angstrom. Second harmonic generation results confirm the structure of Pr3Ti2TaO11 as being noncentrosymmetric. Dense and textured ceramics were prepared by spark plasma sintering. Analysis of the X-ray diffraction and transmission electron microscopy results showed that Pr3Ti2TaO11 ceramics have an n=3 (type II) heteroblock structure consisting of alternating n=2 and 4 octahedral oxide layers. High-resolution electron microscopy revealed the layered structure to be highly disordered, with faulting of the heteroblock structure and the coexistence of a n=4 phase on a fine scale (nm), which was evident as a broadening of the X-ray diffraction peaks of the ceramics. Pr3Ti2TaO11 ceramic exhibits a super-high Curie point (1415 +/- 5 degrees C). A small, but measurable piezoelectric constant d(33) between 0.1 and 0.2pC/N was detected for the samples poled above 900 degrees C under an electric field of 100-200V/cm.