Kui Liu,Liang Shi,Xueying Wang,Cheng Liu,Jie Li,Yulong Liao,Lichuan Jin,Dainan Zhang,Huaiwu Zhang
Herein, Li + -enriched Li (1+ x )2 ZnTi 3 O 8 ceramics are prepared via the solid-phase methods. As x increases, the unit cell volume gradually increases, while the grain size initially increases and then decreases gradually. The Li (1+0.06)2 ZnTi 3 O 8 ceramics exhibit the best dielectric properties : ε r = 25.92, Q × f = 109534 GHz (@7.37 GHz, which is a 48 % increase compared with the stoichiometric counterpart.), and τ f = −8.21 ppm/°C. The complex chemical bond theory and Raman spectroscopy reveal that Ti-O bonds have a significant effect on the dielectric properties . An optimal Li + enrichment leads to an overall reduction in the distortion of the Li/ZnO 4 tetrahedra, resulting in a reduction in τ f . First-principles calculations demonstrate that a suitable excess of Li + leads to an increase in the band-gap as well as an enhanced electron cloud density in the internal space of the Li1/ZnO 4 tetrahedra, thereby increasing the Q × f . In summary, Li + -enriched Li (1+0.06)2 ZnTi 3 O 8 ceramics are promising for a wide array of applications in microwave communications.
The novel low-temperature sinterable 0.6Li 2 ZnTi 3 O 8 –0.4Li 2 TiO 3 ceramics were prepared by cofiring the mixtures of pure-phase Li 2 ZnTi 3 O 8 , Li 2 TiO 3 and ZnO–B 2 O 3 –SiO 2 glass. Li 2 ZnTi 3 O 8 and Li 2 TiO 3 phase could well coexist in the sintered samples with no second phase detected. The near-zero temperature coefficients of the resonant frequency ( τ f ) were achieved and simultaneously the desirable quality factor Q × f values could be maintained. Typically, the 0.6Li 2 ZnTi 3 O 8 –0.4Li 2 TiO 3 ceramics with 1.0 wt% ZBS addition could be well densified at only 900 °C and exhibited excellent microwave dielectric properties of ε r =25.4, Q × f =86,400 GHz and τ f =−1.0 ppm/°C, thus showing a great potential as a middle permittivity low-temperature cofired microwave dielectric material .
Ge Zhang,Wenbo Chen,Yaoan Wang,Xiao Chen,Yanyan Li,Lei Zhao,Yaqiang Yang
In this thesis, a novel ultraviolet-activated Li 2 ZnTi 3 O 8 :Mn 4+ red emitting phosphor is prepared by the traditional high-temperature solid-state reaction method in air. The crystal structure, luminescence properties and decay curves of the phosphor are studied in detail. The sample belongs to spinel cubic crystal structure and there are abundant [TiO 6 ] 8− octahedron sites can be occupied by Mn 4+ . The Li 2 ZnTi 3 O 8 :Mn 4+ phosphor shows the red emission in region of 600–800 nm with a maximum at ~681 nm under 330 nm excitation, which can promote the plant growth. The optimal Mn 4+ doping concentration is ~0.3 mol%, which is higher than that of other hosts. By calculating the crystal field strength (Dq) and Racah parameter B, we can evaluate that there is a strong crystal environment of Mn 4+ in the Li 2 ZnTi 3 O 8 host lattice , which major comes from the 2 E g → 4 A 2g transition of Mn 4+ ion. Furthermore, the characteristics of thermal quenching are also studied, poor thermal quenching performance may be due to high doping concentration of Mn 4+ . All data suggest that Li 2 ZnTi 3 O 8 :Mn 4+ phosphor can be a potential application in plant-cultivation.
Chi Chen,Changchun Ai,Xinyi Liu,Yunwei He,Shi Yang,Yuanxin Wu
Li 2 ZnTi 3 O 8 @C anode material has been synthesized by a facile solid-state reaction method, in which C 6 H 5 Li 3 O 7 ·4H 2 O is used as the lithium source, as well as the single-source carbon. With the formation of carbon-wrapped lithium oxide by the thermolysis of single-component precursor C 6 H 5 Li 3 O 7 ·4H 2 O, Li 2 ZnTi 3 O 8 particles are produced in a limited area, which could effectively hinder their growth/agglomeration. Moreover, the carbon layer coating on the outer surface of Li 2 ZnTi 3 O 8 is also beneficial to the transfer of both Li + and electrons, then an enhanced electrochemical performance is expected to achieve. From the electrochemical test results, a reversible capacity of 227.4 mAh g −1 could be delivered by Li 2 ZnTi 3 O 8 @C after 100 cycles at the current rate of 2 C.
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