arXiv subjects

Duanting Yan

Publications and source records attributed to Duanting Yan.

4 recordsLinked to original sources

arXiv2026

Probing the Effects of Heat Treatment Atmosphere on the Structural and Electrical Properties of NBT via Eu Photoluminescence

The effect of oxygen partial pressure during the pre-calcination step (high vacuum, air, nitrogen, and oxygen) on the crystal structure, microstructure, and electrical properties of Na0.5Bi0.465Sr0.02Eu0.005TiO3 oxide-ion-conducting ceramics was systematically investigated. Dense ceramic samples were prepared by a conventional solid-state reaction route under different atmospheres. The results show that the oxygen partial pressure strongly affects Bi volatilization, grain growth, and oxygen-vacancy concentration. The largest average grain size was obtained for the nitrogentreated sample, whereas the oxygen-treated sample exhibited the finest grains but the highest grain-boundary conductivity. X-ray diffraction and Raman spectroscopy indicate that low oxygen partial pressure enhances structural disorder, while high oxygen partial pressure stabilizes the lattice and promotes charge-transfer transitions. Eu3+ photoluminescence further reveals the correlation between local structural evolution and oxygen-vacancy concentration. These findings clarify how oxygen partial pressure regulates grain-boundary behavior and ion-transport mechanisms in NBT-based oxide-ion conductors, providing guidance for optimizing the total conductivity of polycrystalline electrolytes.

physics.optics↗

arXiv2026

Photoluminescence Identification of Multiple Local Eu3+ Environments in BaTiO3 Ceramics

BaTiO3 is a model ferroelectric perovskite whose properties are highly sensitive to local structure, defect chemistry, and dopant distribution. However, conventional diffraction mainly probes the average lattice and can miss subtle changes in the local coordination environment. Here we use Eu3+ photoluminescence as a local optical probe for BaTiO3 ceramics prepared at 1250, 1300, and 1350 {\deg}C. X-ray diffraction and Raman spectra show that all samples retain the tetragonal BaTiO3 phase within the detection limits of these techniques. Electron microscopy reveals a porous ceramic microstructure with temperature-dependent grain growth, and elemental mapping confirms a spatially distributed Eu signal. The Eu3+ excitation and emission spectra show strong sensitivity to the processing temperature. The sample sintered at 1250 {\deg}C gives the highest emission intensity, while higher sintering temperatures change the relative intensity of the charge-transfer band and the 4f-4f transitions. Most importantly, the 5D0 to 7F0 emission contains two reproducible components near 579.5 nm and 582.2 nm. Their relative weights vary with sintering temperature, and double-exponential decay at 612 nm further supports the presence of multiple Eu-related local environments. These results show that Eu3+ luminescence provides a sensitive route to track local structural heterogeneity in BaTiO3 ceramics.

cond-mat.mtrl-sci↗

arXiv2026

Vacuum-Sealed Thermal Treatment Regulates Trap States and Red Persistent Luminescence in CaTiO3: Pr3+,Al3+ Phosphors

Red persistent phosphors remain less mature than green and blue-green systems because their afterglow is often weak and decays rapidly. Here, CaTiO3:0.3%Pr3+,0.3%Al3+ phosphors were prepared by a high-temperature solid-state route under either air or vacuum-sealed quartz-tube (QT) conditions. The effects of processing atmosphere and sintering temperature on phase structure, microstructure, steady-state photoluminescence, afterglow, thermoluminescence, and excited-state decay were examined. X-ray diffraction and Raman spectra show that all samples retain the orthorhombic CaTiO3 perovskite phase, with no detectable secondary phase. SEM observations show particle coarsening at higher QT temperatures, while EDS mapping indicates a homogeneous distribution of Ca, Ti, O, Pr, and Al within the examined region. The QT-treated samples exhibit stronger Pr3+ red emission near 612 nm and markedly improved afterglow compared with the air-treated sample. The QT-1300 sample shows the best afterglow among the present samples, with a reported 3.6-fold higher intensity at 1200 s than Air-1200{\deg}C. Thermoluminescence results indicate that QT treatment increases the population of thermally active traps and enhances the deeper trap component. These results suggest that a low-oxygen sealed environment regulates defect-related traps, most likely involving oxygen-vacancy-associated centers, and improves carrier storage and release through the Pr3+ and Ti4+ intervalence charge-transfer pathway. This work provides a practical processing strategy for improving CaTiO3-based red persistent phosphors and offers insight into trap-state regulation under low-oxygen thermal treatment.

physics.optics↗

arXiv2026

Processing-Controlled Structural Uniformity and Oxide-Ion Conduction in Na0.52Bi0.47TiO3 Ceramics Probed by Eu3+ Photoluminescence

Sodium bismuth titanate (NBT) is a promising oxide-ion conductor,but its electrical conductivity is highly sensitive to small changes in A-site stoichiometry and processing history.This sensitivity can reduce sample-to-sample reproducibility.Here we examine how precursor mixing controls structural uniformity and ionic transport in Na0.52Bi0.47TiO3 ceramics.Dry grinding,wet grinding with ethanol,and ball milling were compared by X-ray diffraction,electron microscopy,energy-dispersive spectroscopy,Eu3+ photoluminescence excitation spectroscopy,and electrochemical impedance spectroscopy.All processed powders and ceramics form the perovskite NBT phase within the detection limit of XRD.However,the microstructure,surface A-site cation ratio,Eu3+ excitation spectra,and electrical response change strongly with the mixing route.Continuous monitoring of Eu3+ excitation spectra at different emission wavelengths reveals different distributions of local Eu3+ environments.Larger spectral-shape variations are consistent with lower structural uniformity and stronger local distortion.Dry-ground samples show higher bulk conductivity than wet-ground samples,whereas wet-ground samples show much lower grain-boundary resistance.At 600 \u2103,the dry-60 min sample reaches a bulk conductivity of 13.54 mS cm-1,while wet-30 min shows the highest grain-boundary conductivity of 13.72 mS cm-1.These results suggest a processing-driven trade-off between bulk defect generation and grain-boundary blocking.Based on this processing understanding,Ca was introduced at the A site in Na0.52Bi0.47-xCaxTiO3.The x=0.04 sample reaches 8.35 mS cm-1 at 500 \u2103 and 18.98 mS cm-1 at 600 \u2103.

cond-mat.mtrl-sci↗