Search

The effect of multiple-layer bottom electrodes including a La0.5Sr0.5CoO3 (LSCO) layer on the ferroelectric and electric fatigue properties of the PbZr0.5Ti0.5O3 (PZT 50/50) thin film capacitor was investigated. Conductive LSCO thin films consisting of fine perovskite grains can be obtained at relatively low temperatures (400°C) by magnetron sputtering of the ceramic LSCO target. It is found that PZT capacitors having heterostructure electrodes such as Pt/PZT/LSCO/SiO2/Si and Pt/PZT/LSCO/Pt/Ti/SiO2/Si exhibit asymmetric hysteresis loops. These asymmetric capacitors also show fairly good fatigue endurance. Dependence of fatigue on the applied voltage will also be described.

The phase diagram of the 0.5[(1-x)PbYb1/2Nb1/2O3–(x)PbTiO3]–0.5PbZrO3 ceramic system has been determined. A typical relaxor ferroelectric behavior with field dependent hysteresis loops in 0.5PbYb1/2Nb1/2O3–0.5PbZrO3 (x=0) was observed. As the PbTiO3[PT] content increases, however, the relaxor behavior abruptly disappears. The phase at room temperature is a relaxor between x=0 and 0.1, a pseudocubic ferroelectrics (FE) between x=0.1 and 0.4, a rhombohedral FE between x=0.5 and 0.9 and a tetragonal FE between x=0.9 to 1.0. In particular, a morphotropic phase boundary is found to exist between the rhombohedral and tetragonal FE phases in the vicinity of x=0.9.

We have investigated the effect of substitution of La2O3 + Yb2O3 to the perovskite solid solution near the composition (PbYb1/2Nb1/2O3)0.88–(PbTiO3)0.12 in the chemical formula (1-x)[(PbYb1/2Nb1/2O3)0.88 (PbTiO3)0.12]–xLaYbO3. When x = 0.0 and x =0.01, these solid solution have partially disordered pseudocubic structure and behave as a ferroelectric relaxor. For x ≥0.02, the character of phase transition changes from a ferroelectric relaxor type to an antiferroelectric one and the transition temperature surprisingly increases with LaYbO3 addition. In this composition range, the solid solution displays a sharp antiferroelectric transition. The effect on the tendency toward antiferroelecticity with increasing LaYbO3 content is displayed in restoring of the superlattice reflections due to antiferroelectric order. From the structural study of ceramic specimen having various PbTiO3 and LaYbO3 concentration, we have constructed a portion of phase diagram of pseudoternary PbYb1/2Nb1/2O3–PbTiO3–LaYbO3 system.