Flux growth and characterisation of rhombohedral BiFeO3-PbTiO3 single crystals
Single crystals of bismuth ferrite-lead titanate (BFPT) were grown using a flux method. Starting from bismuth ferrite, we added lead titanate, to produce a range of compositions within the BiFeO3-PbTiO3 solid solution, through to the morphotropic phase boundary (MPB). Using a PbO:Bi2O3 flux, and a cooling rate of 0.5°C/h over the temperature range where crystal growth is expected, our aim was to produce highly pure, good size, crack free rhombohedral single crystals. Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) was used to determine the chemical composition and structure of the crystals, and powder X-ray diffraction (XRD) confirmed the crystal structure.
Structure property relations in BiFeO3/BaTiO3 solid solutions
BiFeO3, when forming a solid solution with BaTiO3, shows structural transformations over the entire compositional range. Above 70 mole % of BiFeO3 the structure is rhombohedral and below 4 mole %, it is tetragonal. In between the structure is cubic. The ferroelectric TC decreases with increasing composition of BaTiO3 and a relatively small relaxation is observed. Impedance measurements showed a structural dependence and analysis of which has clearly shown that the capacitance observed is from the bulk of the sample. Relaxation time (τ) of BiFeO3 was estimated using the relaxation times of the intermediate compositions. Magnetization measurements showed field induced ferromagnetism. As the structure becomes cubic with increasing concentration of BaTiO3, paramagnetism sets in, as evidenced by the electron spin resonance spectra.
Assessment of fractures in endodontically treated teeth restored with and without root canal posts using high-resolution cone beam computed tomography
Background Root fractures are a diagnostic challenge for dentists in endodontic treatment. This study aimed to determine the relationship between the characteristics of tooth fractures and the presence of root canal posts in endodontically treated teeth using high-resolution cone beam computed tomography (CBCT). Material and Methods Fifty high-resolution CBCT scans of endodontically treated teeth with a diagnosis of fracture were obtained, of which 30 were from women and 20 were from men. These scans were acquired with three Veraviewepocs 3D units and one 3D Accuitomo 170 unit, with a 40 × 40-mm field of view and 125 μm voxel size. The variables assessed included the type of fracture, extent of fracture, type of retention, post length, cause of endodontic failure, location of the lesion, and time required to detect the fracture (difficulty score). For data analysis, the chi-squared test, Student’s t-test, and multiple linear regression (α <0.05) were used. Results No association was found between the type of fracture and type of retention or between the type of fracture and its extent (P>0.05). On the other hand, the type of fracture significantly influenced the time required for its detection. Additionally, the most difficult plane for detecting the fracture and the difficulty score were associated, with statistically significant results. Conclusions The type of fracture in endodontically treated teeth was not associated with the type of post used for restoration. All of the CBCT systems used to detect tooth fracture showed the same efficiency. Key words:Cone-Beam CT, Tooth Fracture, Root Canal Post.