Electric field and mechanical stress driven structural inhomogeneity and compositionally induced relaxor phase transformation in modified BaTiO3 based lead-free ferroelectrics.

The compositionally induced ferroelectric to relaxor transformation via diffuse phase transition and structural disorder by external stimuli is explored in lead-free Ba1-x (Bi0.5Li0.5) x TiO3 (x = 0, 0.05, 0.1, 0.15, and 0.20) ferroelectric system. X-ray diffraction studies reveal the coexistence of the monoclinic phase along with the orthorhombic and tetragonal phases in BaTiO3, which could be the reason for its superior dielectric properties. The dielectric studies reveal that the x = 0.15 sample shows intrinsic dielectric relaxation due to the quenched-in random field caused by the atomic displacement. The ferroelectric to relaxor phase transformation is analysed by modified Curie-Weiss law. Furthermore, the driving forces for the relaxor behaviour in the system are attributed to the compositionally induced charge disorder, quenched-in random field, and oxygen vacancy related defects in the BBLT system. The detailed structural analysis on the relaxor ferroelectric samples displays direct evidence for the electric field and mechanical stress driven structural inhomogeneity. Notably, mechanically stressed and electrically poled x = 0.15 sample exhibits a remarkable 50% and 37% increase in orthorhombic phase fraction, respectively. Overall, the comprehensive studies on the lead-free modified BaTiO3 samples give further insight into understanding the relaxor system.

Identification of a novel frameshift mutation in PAX6 gene and the clinical management in an Asian Indian aniridia family.

PURPOSE: This study aimed to characterize an Asian Indian aniridia family for both the phenotype and genotype of the disease for a better clinical management. METHODS: The phenotype and genotype of the affected and unaffected individuals in the aniridia family were evaluated. The subjects underwent a standard ophthalmic evaluation followed by molecular screening of PAX6 gene in the peripheral blood for mutation detection. RESULTS: The three affected individuals had aniridia with several common features and an uncommon presentation of bilateral congenital ptosis. Two affected siblings, a brother and a sister, had aniridia, nystagmus, ptosis, increase in central corneal thickness, cataract, and foveal hypoplasia. The sister had features of glaucoma. The offspring of the sister had all the features except cataract and rise in intraocular pressure. Mutation screening of PAX6 gene helped in identifying a novel heterozygous pathogenic variation g. 31801757dupG (c. 216-19dupG) that resulted in a frameshift mutation that extended into exon 7. Based on the evaluation and diagnostic testing, the family was clinically managed along with genetic counselling. CONCLUSION: Molecular diagnostic testing helps in genetic counseling of the family with aniridia to understand the nature of the disease and detection of complications early for better management.