排序方式: 共有8条查询结果,搜索用时 15 毫秒
1
1.
Jakkree Boonlakhorn Narong Chanlek Jedsada Manyam Sriprajak Krongsuk Prasit Thongbai Pornjuk Srepusharawoot 《Ceramics International》2021,47(16):22390-22396
CaCu3-xZnxTi4O12 ceramics (x = 0, 0.05, 0.10) were successfully prepared by a conventional solid-state reaction method. Their structural and dielectric properties, and nonlinear electrical response were systematically inspected. The X-ray diffraction results indicated that single-phase CaCu3Ti4O12 (JCPDS no. 75–2188) was obtained in all sintered ceramics. Changes in the lattice parameter are well-matched with the computational result, indicating an occupation of Zn2+ doping ions at Cu2+ sites. The overall tendency shows that the average grain size decreases when x increases. Due to a decrease in overall grain size, the dielectric permittivity of CaCu3-xZnxTi4O12 decreases expressively. Despite a decrease in the dielectric permittivity, it remains at a high level in the doped ceramics (~3,406–11,441). Besides retention in high dielectric permittivity, the dielectric loss tangent of x = 0.05 and 0.10 (~0.074–0.076) is lower than that of x = 0 (~0.227). A reduction in the dielectric loss tangent in the CaCu3-xZnxTi4O12 ceramics is closely associated with the enhanced grain boundary response. Increases in grain boundary resistance, breakdown electric field, and conduction activation energy of grain boundary as a result of Zn2+ substitution are shown to play a crucial role in improved grain boundary response. Furthermore, the XPS analysis shows the existence of Cu+/Cu2+ and Ti3+/Ti4+, indicating charge compensation due to the loss of oxygen lattice. Based on all results of this work, enhanced dielectric properties of the Zn-doped CCTO can be explained using the internal barrier layer capacitor model. 相似文献
2.
Pariwat Saengvong Narong Chanlek Pornjuk Srepusharawoot Viyada Harnchana Prasit Thongbai 《Journal of the American Ceramic Society》2022,105(5):3447-3455
Various strategies to improve the dielectric properties of ACu3Ti4O12 (A = Sr, Ca, Ba, Cd, and Na1/2Bi1/2) ceramics have widely been investigated. However, the reduction in the loss tangent (tanδ) is usually accompanied by the decreased dielectric permittivity (ε′), or vice versa. Herein, we report a route to considerably increase ε′ with a simultaneous reduction in tanδ in Ta5+–doped Na1/2Y1/2Cu3Ti4O12 (NYCTO) ceramics. Dense microstructures with segregation of Cu– and Ta–rich phases along the grain boundaries (GBs) and slightly increased mean grain size were observed. The samples prepared via solid-state reaction displayed an increase in ε′ by more than a factor of 3, whereas tanδ was significantly reduced by an order of magnitude. The GB–conduction activation energy and resistance raised due to the segregation of Cu/Ta–rich phases along the GBs, resulting in a decreased tanδ. Concurrently, the grain–conduction activation energy and grain resistance of the NYCTO ceramics were reduced by Ta5+ doping ions owing to the increased Cu+/Cu2+, Cu3+/Cu2+, and Ti3+/Ti4+ ratios, resulting in enhanced interfacial polarization and ε′. The effects of Ta5+ dopant on the giant dielectric response and electrical properties of the grain and GBs were described based on the Maxwell–Wagner polarization at the insulating GB interface, following the internal barrier layer capacitor model. 相似文献
3.
Pornjuk Srepusharawoot Ekaphan Swatsitang Vittaya Amornkitbamrung Udomsilp Pinsook Rajeev Ahuja 《International Journal of Hydrogen Energy》2013
This work deals with the investigations of hydrogen adsorption energies of the Li functionalized Covalent Organic Framework-366 (COF-366) by using the density functional theory method. Based on total energy calculations, it was found that Li atom is preferentially trapped at the center site of the tetra(p-amino-phenyl) porphyrin and the onN site of a terephthaldehyde chain. Moreover, hydrogen adsorption energies per H2 for 1–3 H2 loadings range from 0.03 to 0.22 eV. According to ab initio molecular dynamics simulations, our results found that hydrogen capacities of Li functionalized COF-366 at ambient pressure are 2.06, 1.58, and 1.05 wt% for 77, 150 and 298 K, respectively. 相似文献
4.
Jakkree Boonlakhorn Narong Chanlek Jedsada Manyam Sriprajak Krongsuk Pornjuk Srepusharawoot Prasit Thongbai 《Ceramics International》2021,47(12):17099-17108
CaCu3Ti4O12 ceramics have been extensively studied for their potential applications as capacitors in recent years; however, these materials exhibit very large dielectric losses. A novel approach to reducing the dielectric loss tangent in two steps, while increasing the dielectric permittivity, is presented herein. Doping CaCu3Ti4O12 with a Zn dopant reduces the loss tangent of the ceramic material from 0.227 to 0.074, which is due to the increase in grain boundary (GB) resistance by an order of magnitude (from 6.3× 103 to 3.93 × 104 Ω cm). Zn-doping slightly changes the microstructure and dielectric permittivity of the CaCu3Ti4O12 ceramic, which reveals that the primary role of the Zn dopant is to tune the intrinsic properties of the GBs. Surprisingly, the addition of the Ge4+ dopant into the Zn2+-doped CaCu3Ti4O12 ceramic sample led to a further decrease in the loss tangent from 0.074 to 0.014, due to enhanced GB resistance (3.1 × 105 Ω cm). The grain size increased remarkably from 2–3 μm to 85–90 μm, corresponding to a significant increase in the dielectric permittivity (~1–4 × 104). The large increase in GB resistance is due to the intrinsic potential barrier height at the GBs and the segregation of the Cu-rich phase in the GB region. First-principles calculations revealed that Zn and Ge are preferentially located at the Cu sites in the CaCu3Ti4O12 structure. The substitution of the Ge dopant does not hinder the role of the Zn dopant in terms of improving the electrical properties at the GBs. These phenomena are effectively explained by the internal barrier layer capacitor model. This study provides a way of improving the dielectric properties of ceramics for their practical use as capacitors. 相似文献
5.
Jakkree Boonlakhorn Bundit Putasaeng Pinit Kidkhunthod Jedsada Manyam Sriprajak Krongsuk Pornjuk Srepusharawoot Prasit Thongbai 《Journal of the European Ceramic Society》2021,41(10):5176-5183
High dielectric permittivity (ε′ ≈ 2000―6900) was accomplished in Sn4+-doped CaCu2.95Mg0.05Ti4O12 ceramics while retaining a low loss tangent (tanδ ≈ 0.027―0.075). Further, significant improvements in the nonlinear electrical properties, such as high values of the breakdown electric field (Eb ≈ 1.2―1.3 × 104 V cm?1) and nonlinear coefficient (α ≈ 31), were achieved. In addition, the nonlinear electrical parameters significantly improved, which is consistent with the increase in the electrical resistivities of the grains and grain boundaries due to the decrease in the Cu+/Cu2+ ratio. According to our first-principles calculations, the Sn atom at the Ti site prefers to be close to the Mg atom at the Cu site, while the oxygen vacancy prefers to be located at large distances from the Sn and Mg co-dopants. This confirms that the dielectric behavior and the nonlinear electrical properties originate from the interface between the grain and grain boundary. 相似文献
6.
Pornjuk Srepusharawoot Wattana Kosalwat Chesta Ruttanapun 《Journal of the American Ceramic Society》2022,105(3):2067-2081
This study aims to investigate the effect of the phase transition of CuMn1−xCrxO2 compound on the Jahn–Teller effect which in turn affects the optical, thermal, and thermoelectric power factor properties. The CuMn1−xCrxO2 samples were synthesized by a solid-state reaction method. The ab initio computation was applied to evaluate the electronic and optical properties in order to confirm the experiment data. The appearance of the phase transition from crednerite CuMnO2 to delafossite CuCrO2 was confirmed by X-ray diffraction (XRD) and the ab initio computation through displaying the mixed crednerite/delafossite phase; and, the existence of the Jahn–Teller effect was confirmed by the X-ray photoelectron spectroscopy (XPS) technique exhibiting the occurrence of mixed-state Mn3+/Mn4+ ions. The results obtained from XRD, XPS, and the ab initio computation implied the decrease of the Jahn–Teller behavior with increased x content under the influence of the phase transition from the crednerite phase to the delafossite phase of CuMn1−xCrxO2. Surprisingly, the Jahn–Teller distortion reduction caused an increase in the energy gap of the optical property, electrical resistivity, and activation energy in thermally activated band conduction. The effect suffered the specific heat behavior by being separated into two groups of crednerite and delafossite, and enhanced the small polaron behavior by increasing the activation energy of thermally activated band conduction. The phase transition reduced the results of thermal conductivity, thermopower, and thermoelectric power factor properties. In other words, the effect of the phase transition from the crednerite CuMnO2 phase to the delafossite CuCrO2 phase on CuMn1−xCrxO2 compound reduced the Jahn–Teller effect with increased Cr content which in turn caused changes in the optical, thermal, and thermoelectric power factor properties. The effect of the phase transition is advantageous for the improvement of material properties. 相似文献
7.
Prasan Primprapha Aunping Namfon Chanlek Narong Kumlangwan Pantiwa Towannang Madsakorn Klangtakai Pawinee Srepusharawoot Pornjuk Thongnum Anusit Kumnorkaew Pisist Jarernboon Wirat Pimanpang Samuk Amornkitbamrung Vittaya 《Journal of Materials Science: Materials in Electronics》2022,33(3):1589-1603
Journal of Materials Science: Materials in Electronics - CH3NH3PbI3 perovskite films were prepared via a hot-casting method using six different CH3NH3I, PbI2 and Pb(SCN)2 solutions. Surface... 相似文献
8.
Jakkree BOONLAKHORN Narong CHANLEK Jedsada MANYAM Pornjuk SREPUSHARAWOOT Sriprajak KRONGSUK Prasit THONGBAI 《先进陶瓷(英文版)》2021,(6):1243-1255
The giant dielectric behavior of CaCu3Ti4O12 (CCTO) has been widely investigated owing to its potential applications in electronics; however, the loss tangent (... 相似文献
1