“…Among these ceramics, the sample with x = 0.025 showed the minimum tanδ of ~0.11 and colossal permittivity (ε ~4.8 × 10 4 ) at 10 kHz and room temperature. This dielectric performance is close to that of (Nb, La) [25], (Ta, In) [6] and (Nb, Eu) [28] co-doped TiO 2 but lower than (Ta, Mg) [29], (Ta, Y) [30] (Ta, Ho) [31] (Nb, Zr) [14] co-doped TiO 2 . Figure 5 depicts the room temperature complex impedance (Z* = Z + iZ ) plots for the four ceramic samples.…”
(Nb5+, Si4+) co-doped TiO2 (NSTO) ceramics with the compositions (Nb0.5Si0.5)xTi1−xO2, x = 0, 0.025, 0.050 and 0.1 were prepared with a solid-state reaction technique. X-ray diffraction (XRD) patterns and Raman spectra confirmed that the tetragonal rutile is the main phase in all the ceramics. Additionally, XRD revealed the presence of a secondary phase of SiO2 in the co-doped ceramics. Impedance spectroscopy analysis showed two contributions, which correspond to the responses of grain and grain-boundary. All the (Nb, Si) co-doped TiO2 showed improved dielectric performance in the high frequency range (>103 Hz). The sample (Nb0.5Si0.5)0.025Ti0.975O2 showed the best dielectric performance in terms of higher relative permittivity (5.5 × 104) and lower dielectric loss (0.18), at 10 kHz and 300 K, compared to pure TiO2 (1.1 × 103, 0.34). The colossal permittivity of NSTO ceramics is attributed to an internal barrier layer capacitance (IBLC) effect, formed by insulating grain-boundaries and semiconductor grains in the ceramics.
“…Among these ceramics, the sample with x = 0.025 showed the minimum tanδ of ~0.11 and colossal permittivity (ε ~4.8 × 10 4 ) at 10 kHz and room temperature. This dielectric performance is close to that of (Nb, La) [25], (Ta, In) [6] and (Nb, Eu) [28] co-doped TiO 2 but lower than (Ta, Mg) [29], (Ta, Y) [30] (Ta, Ho) [31] (Nb, Zr) [14] co-doped TiO 2 . Figure 5 depicts the room temperature complex impedance (Z* = Z + iZ ) plots for the four ceramic samples.…”
(Nb5+, Si4+) co-doped TiO2 (NSTO) ceramics with the compositions (Nb0.5Si0.5)xTi1−xO2, x = 0, 0.025, 0.050 and 0.1 were prepared with a solid-state reaction technique. X-ray diffraction (XRD) patterns and Raman spectra confirmed that the tetragonal rutile is the main phase in all the ceramics. Additionally, XRD revealed the presence of a secondary phase of SiO2 in the co-doped ceramics. Impedance spectroscopy analysis showed two contributions, which correspond to the responses of grain and grain-boundary. All the (Nb, Si) co-doped TiO2 showed improved dielectric performance in the high frequency range (>103 Hz). The sample (Nb0.5Si0.5)0.025Ti0.975O2 showed the best dielectric performance in terms of higher relative permittivity (5.5 × 104) and lower dielectric loss (0.18), at 10 kHz and 300 K, compared to pure TiO2 (1.1 × 103, 0.34). The colossal permittivity of NSTO ceramics is attributed to an internal barrier layer capacitance (IBLC) effect, formed by insulating grain-boundaries and semiconductor grains in the ceramics.
“…Usually, after the introduction of the co‐dopant, more carriers are accumulated at the ceramic grain boundaries, resulting in a huge grain boundary polarization 24 . To visually analyze the dielectric properties of (Tb 0.5 Ta 0.5 ) x Ti 1− x O 2 ceramics, the ε r and tan δ values of (Tb 0.5 Ta 0.5 ) 0.005 Ti 0.995 O 2 ceramic were compared with those of dielectric ceramics previously described in the literature, as shown in Figure 4 1,5,11,14,20,27–38 . It is clear that the (Tb 0.5 Ta 0.5 ) 0.005 Ti 0.995 O 2 ceramics have large ε r with very low tan δ , indicating the excellent dielectric properties in this work.…”
The environment-friendly materials exhibiting colossal permittivity play an increasingly important role in the electronics industry. In this work, (Tb 0.5 Ta 0.5 ) x Ti 1−x O 2 (x = 0, 0.005, 0.01, 0.02, and 0.04) ceramics with new defect clusters were fabricated to enhance the dielectric response. Significantly, all ceramic samples exhibit large dielectric constants (ε r > 10 4 ), whereas the ceramic with x = 0.005 exhibits an ultralow loss (tan δ) of about 0.008 at room temperature and 1 kHz. The origins of its excellent dielectric properties were revealed by XRD, X-ray photoelectron spectroscopy, and dielectric response analysis, which were mainly caused by defective dipoles associated with oxygen vacancies (𝑉 •• O ). These defective dipoles limiting the long-range hopping of electrons lead to the electron pinning effect. Additionally, the frequency spectrum under DC bias and conductivity behavior suggests that grain boundary and electrode effects also contribute to the dielectric constant. This study not only explores the dielectric response properties of a new giant dielectric (Tb 0.5 Ta 0.5 ) x Ti 1−x O 2 ceramics but also offers a candidate material suitable for ceramics capacitors.
“…As indicated by the Ho4d 5/2 and Ho4d 3/2 peaks at 160.5, 163.1, 161.6, and 163.7 eV, for metallic Ho 0 and Ho 3+ , respectively. (Fan et al 2021 ; Osial et al 2018 ; Yin 2013 ). Fig.…”
In the search of novel photocatalysts to increase the effect of visible light in photocatalysis, g-C3N4 (CN) has become a shining star. Rare earth metals have been used as dopant material to reinforce the photocatalytic activity of CN due to their unique electron configuration recently. In this present study, the pure and different amounts of Ho-doped g-C3N4 (HoCN) photocatalysts were successfully synthesized using urea as a precursor by the one-pot method. Morphological, structural, optical, and vibrational properties of the synthesized photocatalysts were characterized by SEM, EDX, XRD, TGA, XPS, FTIR, PL, TRPL, Raman, DRS, and BET analyses. In addition, theoretical calculations using density functional theory (DFT) were meticulously carried out to delve the changes in the structural and electronic structure of CN with holmium doping. According to calculations, the chemical potential, electrophilicity, and chemical softness are higher for HoCN, while HOMO–LUMO gap, dipole moment, and the chemical hardness are lower for the pure one. Thus, holmium doping becomes desirable with low chemical hardness which indicates more effectivity and smaller HOMO–LUMO gap designate high chemical reactivity. To determine the photocatalytic efficiency of the pure and doped CN photocatalysts, the degradation of methylene blue (MB) was monitored under visible light. The results indicate that holmium doping has improved the photocatalytic activities of CN samples. Most strikingly, this improvement is noticeable for the 0.2 mmol doped CN sample that showed two times better photocatalytic activity than the pure one.
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