Volume 91, Issue 12, 15 June 2002
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
91(2002); http://dx.doi.org/10.1063/1.1480114View Description Hide Description
The (BSR) oxide electrode which can enhance electrical properties of (BST) dielectric film due to structural and chemical matches with BST, was evaluated as an oxygen diffusion barrier. It was possible to restrain the oxidation of TiN layer under BSR to by sequential depositions of amorphous BSR and crystalline BSR, in which the amorphous BSR eventually crystallized into crystalline BSR during the deposition of crystalline BSR. When two-step BSR layers on TiN, however, were annealed in oxygen ambient at 700 °C, oxygen atoms diffused and oxidized TiN layer to On the other hand, oxygen could be effectively blocked by the BSR/Ru bilayer. In this system, the Ru sublayer plays a role as an oxygen getter and the bilayer tends to block oxygen diffusion. The blocking effect was more obvious when the thickness of BSR in the bilayer increased. The BST/bilayer showed higher dielectric constant due to the suppression of formation of a low dielectric layer between BST and the bilayer. Although the BST/bilayer showed a slightly higher leakage current density, it was possible to reduce the leakage current density to order A/cm2 at 1 V by increasing the BSR thickness in the bilayer.
Field-enhanced piezoelectric deformation during the high temperature/low temperature rhombohedral phase transformation for tin modified lead zirconate titanate ceramics91(2002); http://dx.doi.org/10.1063/1.1479468View Description Hide Description
An unusual field-enhanced piezoelectric deformation near the structuralphase transformation was observed in a tin modified lead zirconate titanatesolid solution. In addition to the typical field-induced domain reorientation and the piezoelectric strain, this additional field-enhanced deformation only observed near the phase transformation increases linearly with external electric field strength. A 78% increase in field-enhanced strain was observed at a field strength of 32 kV/cm. Comparison of the dielectric susceptibility at low and high field conditions suggests that the observed unusual behavior is created by a field-induced lattice softening during the structuralphase transformation. Experimental observations on the field-induced softening phenomena are reported.
91(2002); http://dx.doi.org/10.1063/1.1480110View Description Hide Description
Vanadium-doped strontiumbismuthtantalate (SBTV) have been prepared on substrates using a metalorganic decomposition method. Well-crystallized and dense SBTV films can be obtained at an annealing temperature as lower as 650–700 °C that can be attributed to the enhanced densification due to the addition of vanadium. With partial substitution of tantalum by vanadium up to a larger remanent polarization of 30.5 μC/cm2 can be obtained for the film at 800 °C that is attributed to the larger grain size and increased “rattling space.” Furthermore, the vanadium substitution for tantalum ion can effectively reduce the leakage current density as lower as at an applied electric field of 100 kV/cm because of the reduced mobility of charge carriers. However, the incorporation of vanadium does not cause appreciable negative effect on the fatigue endurance of Sr-deficient films until more than 20 mol % vanadium was added.
91(2002); http://dx.doi.org/10.1063/1.1481771View Description Hide Description
Ferroelectricphase transformationcharacteristics of ceramic have been studied by combined thermo-Raman and dielectricmeasurements. The temperature dependence of Raman bands at 311 and 721 shows that tetragonal to cubic phase transformation occurs over a range of temperature. The increase in the bandwidths of these bands indicates that this transformation is an order-disorder transformation. The differential thermo-Raman intensity thermograms show a dip at a temperature corresponding to the maximum rate of phase transformation and this temperature can be defined as phase transformationtemperature The ferroelectric transformationtemperature corresponding to the peak in the obtained from the temperature dependence of dielectric constant is found to coincide with This indicates that maximum in dielectric constant occurs at the maximum rate of phase transformation. Both and exhibit thermal hysteresis. The Curie temperature obtained from the intersection of tangential of inverse dielectric constant to the temperature axis and is found to be less than and in agreement with O. G. Vendik and S. P. Zubko [J. Appl. Phys. 88, 5343 (2000)] calculations. Thermo-Raman spectroscopy coupled with dielectric constantmeasurement is shown to be an effective technique to investigate the phase transformation in ferroelectric materials.