An x-ray study of the lead zirconate-bismuth ferrate system

The lead zirconate-bismuth ferrate system was studied employing x-ray and microscopic analysis. Samples were prepared by sintering stoichiometric mixtures of the corresponding oxides followed by air quenching. The results of the analyses show the system to be probably solid solutions over the entire compositional range, although small amounts of other phases are present in some regions. X-ray data indicate a multiple cell, orthorhombic phase, to exist over the range 100-30 mole percent PbZrO₃ . From 100-82 mole percent PbZrO₃ , the addition of BiFeO₃ reduces the distortion of the phase such that a nearly cubic x-ray pattern is obtained at approximately 80 mole percent PbZrO₃. In the same range dielectric measurements suggest antiferroelectric properties. The nearly cubic phase is also confirmed by a minimum in a plot of Curie points versus composition. From 80-30 mole percent PbZrO₃ the structure is only slightly distoxted from that at 80 mole percent PbZrO₃ . In the range 80-50 mole percent PbZrO₃, the system is apparently ferroelectric. Samples of composition greater than 50 mole percent BiFeO₃ are too conductive for meaningful dielectric measurements. A rhombohedral phase corresponding to that of pure BiFeO₃ is observed from approximately 75-100 mole percent BiFeO₃. The electrical properties of the solid solutions in the range from 100-50 mole percent PbZrO₃ are explained on the basis of a structural model of crystalline PbZrO₃ proposed by previous investigators --Abstract, pages ii-iii

Ferroelectric Properties of PbZrO₃-BiFeO₃ Solid Solutions

Solid solutions of BiFeO and PbZrO3 were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, which has been tentatively indexed as orthorhombic with the same unit cell as PbZrO3 but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has a minimum of about 155°C at a composition of about (PbZrO3)0.80 (BiFeO3)0.20, which at room temperature lies on the boundary between the orthorhombic antiferroelectric and the pseudocubic ferroelectric phases. This composition has a relative dielectric constant of 800 at room temperature and shows appreciable dielectric nonlinearity. The Curie point rises to about 400°C for (PbZrO3)0.50 (BiFeO3)0.50 and is extrapolated to about 900°C for pure BiFeO3, in agreement with previous data from similar solid solutions. It is felt that this is additional evidence that the distortion from cubic symmetry in BiFeO3 may be of ferroelectric origin

Epigenotype, Genotype, and Phenotype Analysis of Taiwanese Patients with Silver–Russell Syndrome

Background: Silver–Russell syndrome (SRS) is a clinically and genetically heterogeneous disorder characterized by severe intrauterine growth retardation, poor postnatal growth, characteristic facial features, and body asymmetry. Hypomethylation of the imprinted genes of the chromosome 11p15.5 imprinting gene cluster and maternal uniparental disomy of chromosome 7 (mUPD7) are the major epigenetic disturbances. The aim of this study was to characterize the epigenotype, genotype, and phenotype of these patients in Taiwan. Methods: Two hundred and six subjects with clinically suspected SRS were referred for diagnostic testing, which was performed by profiling the methylation of H19-associated imprinting center (IC) 1 and the imprinted PEG1/MEST region using methylation-specific multiplex ligation-dependent probe amplification and high-resolution melting analysis with a methylation-specific polymerase chain reaction assay. We also applied a whole genome strategy to detect copy number changes and loss of heterozygosity. Clinical manifestations were recorded and analyzed according to the SRS scoring system proposed by Bartholdi et al. Results: Among the 206 referred subjects, 100 were classified as having a clinical diagnosis of SRS (score ≥ 8, maximum = 15) and 106 had an SRS score ≤ 7. Molecular lesions were detected in 45% (45/100) of the subjects with a clinical diagnosis of SRS, compared to 5% (5/106) of those with an SRS score ≤ 7. Thirty-seven subjects had IC1 hypomethylation, ten subjects had mUPD7, and three subjects had microdeletions. Several clinical features were found to be statistically different (p < 0.05) between the “IC1 hypomethylation” and “mUPD7” groups, including relative macrocephaly at birth (89% vs. 50%), triangular shaped face (89% vs. 50%), clinodactyly of the fifth finger (68% vs. 20%), and SRS score (11.4 ± 2.2 vs. 8.3 ± 2.5). Conclusions: The SRS score was positively correlated with the molecular diagnosis rate (p < 0.001). The SRS subjects with mUPD7 seemed to have fewer typical features and lower SRS scores than those with IC1 hypomethylation. Careful clinical observation and timely molecular confirmation are important to allow for an early diagnosis and multidisciplinary management of these patients