The polarization of PbTiO3/SrTiO3 superlattices is experimentally tuned from 0–60 μC/cm–2 and the transition temperature from room temperature to 1000 K while maintaining a perfect crystal structure ...and low leakage currents (see figure). A simple model based on Landau theory is developed as a guide for the straightforward production of samples with ferroelectric properties designed for particular applications.
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The dielectric response of PbTiO(3)/SrTiO(3) superlattices is studied using electrical and structural measurements. While the dielectric response of paraelectric superlattices is well accounted for ...by the lattice contribution, superlattices with ferroelectric compositions exhibit an enhanced permittivity. X-ray diffraction allowed the presence of ordered nanodomains in ferroelectric superlattices to be established and their displacement under an applied bias to be directly probed, demonstrating that the enhanced permittivity in these artificial materials is due to domain wall motion.
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Terbium-152 is one of four terbium radioisotopes that together form a potential theranostic toolbox for the personalised treatment of tumours. As 152 Tb day by positron emission it can be utilised ...for diagnostics by positron emission tomography. For use in radiopharmaceuticals and for activity measurements by an activity calibrator a high radionuclide purity of the material and an accurate and precise knowledge of the half-life is required. Mass-separation and radiochemical purification provide a production route of high purity 152Tb. In the current work, two mass-separated samples from the CERN-ISOLDE facility have been assayed at the National Physical Laboratory to investigate the radionuclide purity. These samples have been used to perform four measurements of the half-life by three independent techniques: high-purity germanium gamma-ray spectrometry, ionisation chamber measurements and liquid scintillation counting. From the four measurement campaigns a half-life of 17.8784(95) h has been determined. The reported half-life shows a significant difference to the currently evaluated half-life (ζ-score = 3.77), with a relative difference of 2.2 % and an order of magnitude improvement in the precision. This work also shows that under controlled conditions the combination of mass-separation and radiochemical separation can provide high-purity 152Tb.
•First half-life measurement of 152Tb since 1970.•Precise half-life of 152Tb determined by three independent techniques from mass-separated samples.•Presented half-life value shows a relative difference of 2.2% from current evaluated value.•Order of magnitude improvement in the precision to the current evaluated value.•Radionuclide contaminants from two mass-separated samples assessed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We present a brief review of the role of interfacial physics in ferroelectric oxides, with an emphasis on the importance of boundary conditions that determine the properties of very thin ...ferroelectric films and superlattices. As well as discussing the screening problem, and the role of strain and electrostatics in ferroelectrics, we highlight some of the possibilities in fine period superlattices where the high density of interfaces can lead to new and potentially useful phenomena.
The effect of the Jasper Jumper in the treatment of Class II, division 1 malocclusions was studied in 26 consecutive 13-25-year-old patients. The median treatment time was 5 months, followed by a ...median period of observation or retention of 7 months. The effects of the treatment were evaluated from cephalograms taken before the treatment, at the removal of the Jumpers and at the end of the period of observation or retention. The Jumpers brought about a slight retrusion of the maxilla and markedly increased the mandibular prognathism. The maxillary incisors and molars were retruded, and the mandibular incisors and molars protruded. The median correction of the overjet was almost 5 mm and of the molar relationship 3 mm. The intrusive forces of the Jumper resulted in a transient intrusion of the maxillary molars and the mandibular incisors. After the period of retention and observation, the dento-alveolar effects had partially or totally relapsed. The remaining effect contributing most to the correction was the skeletal effect on the mandible, i.e. the increase in mandibular prognathism. The skeletal mandibular effect was the same in younger and older subjects. At the end of observation about 60 per cent of the overjet reduction and 75 per cent of the molar correction remained. The incidence of breakage of the Jumpers was 9 per cent.
Artificial PbTiO3/SrTiO3 superlattices were constructed using off-axis rf magnetron sputtering. X-ray diffraction and piezoelectric atomic force microscopy were used to study the evolution of the ...ferroelectric polarization as the ratio of PbTiO3 to SrTiO3 was changed. For PbTiO3 layer thicknesses larger than the 3-unit cell SrTiO3 thickness used in the structure, the polarization is found to be reduced as the thickness is decreased. This observation confirms the primary role of the depolarization field in the polarization reduction in thin films. For the samples with ratios of PbTiO3 to SrTiO3 of less than one, a surprising recovery of ferroelectricity that cannot be explained by electrostatic considerations was observed.
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Polydomain superlattices composed of ferroelectric PbTiO
3
and paraelectric SrTiO
3
were investigated by means of temperature-dependent X-ray diffraction and electrical measurements. The ...ferroelectric nanodomains were found to have an almost isotropic distribution of domain wall alignments and to be highly responsive to applied electric fields, giving rise to large enhancements in the overall dielectric response of the structure. Electrical measurements revealed a dramatic dependence of the dielectric permittivity, tunability, and polarization-voltage characteristics on the superlattice period. For short-period superlattices, double hysteresis loops were observed.
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