CHARACTERIZATION OF STRUCTURAL, THERMAL, ELECTRICAL, AND MORPHOLOGICAL PROPERTIES OF BI2O3 ELECTROLYTES CO–DOPED WITH LANTHANIDE OXIDES

Due to their outstanding oxygen ion conductivity, face-centered cubic–Bi2O3 materials (δ-phase) are thought of as a good solid electrolyte selection for low-temperature SOFC applications. When stabilized at room temperature, this highly ion-conducting phase could provide an appropriate replacement to the YSZ electrolytes widely employed in today's SOFC technology. In this study, pure Bi2O3 powders were doped with rare earth oxide powders using a solid–state process under atmospheric circumstances. The XRD patterns indicate that samples A1 (20% doped), A2 (35% doped), and B2 (40% doped) are stabilized with a single cubic phase, and their lattice constants are lower in comparison to the pure phase, as predicted. Due to the absence of endothermic or exothermic peaks in the pattern, DTA curves imply that there is no phase transition. Arrhenius plots demonstrate that increasing the dopant rate has a significant influence on conductivity. Sample B1 (25% doped) exhibits a maximum conductivity of 0.0228 S.cm-1 and an activation energy of 0.86 eV at 750 °C. The grain sizes are not uniform over the surface of the A-series samples, and the grain boundary rapidly changes as the dopant density in the mix increases. Furthermore, the porous structures that appear on the surface as doping increases could be responsible for the notable decrease in conductivity. The EDAX pattern of sample A1 indicated that all components of the mixture were present in the compositions with no unwanted impurities.</p

FABRICATION AND CHARACTERIZATION OF TB-SM-GD CO-DOPED BI 2 O 3 ELECTROLYTES FOR INTERMEDIATE TEMPERATURES

A high ion conductivity, face-centered cubic δ-Bi2O3 material is regarded as a significant solid electrolyteoption, particularly for low-temperature SOFC applications. Stabilizing this phase while retaining the majorityion conductivity might allow it a competitive advantage in IT-SOFC electrolyte candidacy. It is well acceptedthat δ-Bi2O3 has stronger conductivity than the YSZ electrolytes commonly utilized in HT-SOFC units. Thecurrent work focuses on the structural, thermal, surface, and conductivity properties of Bi2O3 electrolytes co-doped with Tb-Sm-Gd. With the exception of sample 20Tb20Sm20Gd, the XRD outcomes suggest that allsamples are stabilized by cubic δ-phase at room temperature. The computed lattice constants also show unit cellshrinkage, showing that the partial cation substitutions of Bi3+ and lanthanide cations are successful. There areno endothermic or exothermic peaks on the DTA curves, indicating a probable phase transition. ConductivityArrhenius graphs show that conductivity decreases as the dopant ratio increases, suggesting a decrease inpolarization power due to cationic substitution. This study's highest conductivity is 0.131 S/cm for sample10Tb10Sm10Gd, with a total doping rate of 30%. The FE-SEM images clearly point out that doping has asignificant impact on grain size and boundaries. Moreover, the pores on the surface are probably responsible forthe decrease in conductivity resulting from doping. The EDAX pattern of sample 10Tb10Sm10Gd also provesthe combination includes all of the elements, as there are no peaks implying impurities.</div

SYNTHESIS AND CHARACTERIZATION OF THE Bi2O3 ELECTROLYTES DOPED WITH CeO2, Ho2O3 and Tb4O7 RARE EARTHS

In this study, the synthesis and characterization of stabilized Bi2O3 solid electrolyte systems, especiallyfor the intermediate–temperature Solid Oxide Fuel Cells (IT–SOFCs), were performed. It is well knownthat the face–centered cubic structure of pure Bi2O3 crystal exhibits unusual oxygen ion conductivity.However, the super–ion conductor in this phase is stable over a very narrow temperature range, and thusit needs to be stabilized for SOFC candidacy. For the stability study, Ce–Ho–Tb rare earth elementswere used as dopants, and all compositions were synthesized by solid–state reactions at roomtemperature. To obtain ideal phase–stable materials the produced samples were annelaed at 750 °C for100 hour. Annealed samples were characterized by a series of experimental studies, including X–RayDiffraction (XRD), Thermogravimetry and Differential Thermal Analysis (TG and DTA), Four PointTip Method (FPPT), and Field Emission–Scanning Electron Microscope (FE–SEM). Among allsamples, the Ce–rich ones exhibited the highest values in electrical conductivity, especially at the 2:1:1dopant content ratio. Here, it was observed that the cation polarizability had a serious effect on theconductivity results. On the other hand, the XRD patterns clearly revealed that the diffraction peak ofthe (111) plane shifted as the doping concentration increased, indicating that the partial cation exchangewas successful in the crystal lattice. The crystal phase transition (α→δ) was quite evident on the DTA&nbsp;curves of samples 4Ce4Ho4Tb and 4Ce4Ho8Tb. In this study, the highest electrical conductivity at 700°C was obtained for sample 8Ce4Ho4Tb with 0.30 S/cm. FE–SEM images clearly indicated theaggregation of atoms in Ce–rich samples. Besides, FE–SEM images of Tb–rich samples heavilyincluded surface holes predicted to cause doping–index conductivity decay.Keywords: Phase transition, Solid oxide fuel cell, Lattice contraction, Microstrain, Grain size andboundary.&nbsp;</p

A STUDY ON THE ELECTRICAL CONDUCTIVITY AND PHASE STABILITY OF THE (Bi2O3)1–x-y (Tm2O3)x (Yb2O3)y DOUBLE–DOPED ELECTROLYTES AT INTERMEDIATE TEMPERATURES

Due to its superior ion conductivity, face–centered cubic–Bi2O3 (δ–phase) material has been recognizedas suitable solid electrolytes in terms of the Intermediate Temperature–Solid Oxide Fuel Cells (IT–SOFCs) applications. Interestingly, the highest conductivity values reported for cubic–stabilized Bi2O3electrolytes have been achieved by employing the double doping approach, relying on co–dopantcontent ratios of 2:1 or 1:2. In the present study, ceramic compositions of Bi2O3 co–doped with Tm–Yb rare earths have been developed using solid–state techniques. For stability of δ–phase, allcompositions were then subjected to heat treatment at 750 °C for 100 hours. Annealed samples werecharacterized by several experimental studies including X–Ray Diffraction (XRD), Termogravimetricand Diffeantial Thermal Analysis (TG &amp; DTA), Four Point Probe Technique (FPPT), And FieldEmission–Scanning Electron Microscope (FE–SEM). The conductivity of sample 8Tm4Yb createdusing a content ratio of 2:1 is 0.432 S/cm at 700 °C, outperforming that of single–doped 20ESBelectrolytes. Arrhenius plots of conductivity in Tm–rich materials also showed that it increased withdoping rate, reflecting an increase in oxygen–unoccupied concentration. In many samples, the order–disorder transitions (ODT) and phase transition (α→δ) were clearly apparent on DTA curves andArrhenius plots. The FE–SEM images of the Tm–rich samples revealed a reduction in particle size with&nbsp;doping, which was directly related to the lattice strain caused by doping. Additionally, surface holeswere visible in FE–SEM images of Tb–rich samples, which could result in a decline in electricalconductivity.Keywords: Phase transition, Ion conductivity, Unit cell contraction, Electrical activation energy,Average crystal size.&nbsp;</p

Retromolar canal as observed on cone-beam computed tomography: Report of two cases with clinical importance

The retromolar canal (RMC) is an anatomical structure of the mandible with the clinical importance for surgical procedures such as impacted molar extraction and sagittal split ramus osteotomy. Since the RMC has omitted in anatomical textbooks and has rarely been reported in the dental literature, awareness of this condition is important. The aim of this study was to describe two cases of RMC and foramen on the basis of cone beam computed tomography images: One in a 53-year-old female and the other in a 64-year-old female. The authors believe that the present study will aid to the confirmation of the "RMC;" thus, permitting the planning of surgery with a lower risk of surgical damage

Evaluation of location and dimensions of mandibular lingual foramina using cone-beam computed tomography

The aim of this study was to assess the regional frequency and anatomical properties of mandibular lingual foramina (MLF) and their bony canals with cone-beam computed tomography (CBCT)

An investigation on the phase formation and electrical properties of Bi2O3 ceramics co–doped with Ce–Ho–Tb rare earths

In this paper, Ce–Ho–Tb co–doped Bi2O3&nbsp;compositions were developed using the solid–state reaction method under atmospheric conditions. The XRD patterns confirm the stability of the cubic δ–phase in Ho and Tb–rich compositions but not in the Ce–rich ones, which consist of mixed phases, such as α and β. Peak shifting is additionally apparent in the magnified XRD diagram of primary peaks regarding the (111) diffraction plane, suggesting that the structural features change with doping. At 700&nbsp;°C, the highest conductivity is found to be 0.30&nbsp;S/cm for the composition 8Ce4Ho4Tb, and it is comparable to the single–doped (Bi2O3)0.80(Er2O3)0.20&nbsp;system at the same temperature. The FE–SEM images show the aggregation, particularly in images of Ce–rich compositions, implying that large cations have difficulty penetrating the lattice. The porosity over the surface is dense, particularly for Tb–rich compositions, indicating a decline in conductivity with doping.</p

Assessment of the Visibility and Characteristics of the Mandibular Incisive Canal: Cone Beam Computed Tomography Versus Panoramic Radiography

Purpose: The aim of this study was to assess and compare the visibility, diameter, and course of the mandibular incisive canal (MIC) using cone beam computed tomography (CBCT) and panoramic radiography. Materials and Methods: CBCT images and panoramic radiographs from 243 patients were used in this. study. Standard exposure and patient positioning protocols were used for all the patients. Both types of images were assessed by two dentomaxillofacial radiologists. The diameter and the endpoint level of the MID were measured using the CBCT images. Statistical analysis was performed using t tests in statistical software. Results: Of the 486 hemimandibles examined, the MIC was visible in 249 (51.2%) radiographs and 459 (94.4%) CBCT images. The mean diameters of the MICs were 1.91 +/- 0.45 mm on the right side and 1.94 +/- 0.41 mm on the left side. The MICs on both the right and left sides of the mandible showed statistically significant differences in diameter in male versus female patients. The visibility of the MIC on the panoramic radiographs according to the increase in the diameter was not statistically significant for both sides. Twenty MICs reached to the midline of the mandible, and the majority of the MICs (n = 114) terminated between the canine and the first premolar. Conclusion: The visibility of the MIC in CBCT is much better than that observed in conventional panoramic radiography. Even some large MICs could not be observed in panoramic radiographs. Detection of the MIC using CBCT may be crucial for surgical procedures involving the inter foraminal region