Low-temperature fired thermal-stable Li2TiO3–NiO microwave dielectric ceramics

Abstract

Rock salt-structured (1 -x)Li 2 TiO 3 -xNiO (0 B xB0.5) solid solutions were prepared via a conventional solid-state method. The structure evolution, sintering behavior, and microwave dielectric properties were investigated systematically. The phase transition from an ordered monoclinic to a disordered cubic phase was observed as x increased from 0 to 0.4. Disordered cubic phases in x = 0.4-0.5 samples seemed to conform to the structure of LiTiO 2 instead of Li 2 TiO 3 . The possible reason was ascribed to both the appearance of Ti 3? in the NiOmodified matrix and the lattice distortion from substituted ions with different radii. With a gradual decline of the structure order degree, s f was found to decrease from ?26 to -36 ppm/°C. A greatly improved Q 9 f value of 103,050 GHz (at 7.65 GHz) could be yielded at x = 0.1 owing to the increased packing fraction. The 0.8Li 2 TiO 3 -0.2NiO ceramic exhibited excellent overall microwave dielectric properties of e r = 20.4, Q 9 f = 83,608 GHz (at 7.63 GHz) and s f = 1.97 ppm/°C as sintered at 1250°C. After the addition of 1 wt% BaCuB 2 O 5 , the x = 0.2 ceramic can be well densified at 850°C and chemically compatible with pure silver, in addition to keeping superior properties of e r = 19, Q 9 f = 62,252 GHz (at 7.84 GHz) and s f = -1.65 ppm/°C. All the above results indicate that the current material system would be a promising candidate for the application of low-temperature co-fired ceramics.

Temperature Stability of Li2TiO3‐Zn2SiO4 Microwave Dielectric Ceramics

“…[16] And the porous microstructures were also observed in the Li 2 TiO 3 ceramics with MgO, ZnO and NiO in the previous works. [21,22,27] All specimens showed porous microstructure, which was similar to that of Li 2 TiO 3 system in the previous studies. [21,22] The porous microstructure can be attributed to the evaporation of lithium.…”

“…Previous studies show that it is difficult to obtain high densification pure Li 2 TiO 3 ceramics by conventional solid‐state method [16] . And the porous microstructures were also observed in the Li 2 TiO 3 ceramics with MgO, ZnO and NiO in the previous works [21,22,27] . All specimens showed porous microstructure, which was similar to that of Li 2 TiO 3 system in the previous studies [21,22] .…”

Unexplored Orthorhombic LiMn1–xTixO2 Cathode Materials with a Stable Atomic Site Occupancy and Phase Transition

“…However, according to the literature, c-Li 2 TiO 3 (γ phase) is more stable than m-Li 2 TiO 3 at high temperatures (≤1050 °C). 56,57 In addition, there are a significant number of oxygen vacancies in o-LiMn 1−x Ti x O 2 (x = 0.05, 0.1), as confirmed by the previous Rietveld refinement analysis. Therefore, c-LiTiO 2 was preferred as a secondary phase in o-LiMn 1−x Ti x O 2 (x = 0.05, 0.1) over m-Li 2 TiO 3 due to the partial loss of oxygen ions and preference for the cubic crystal structure during the synthesis (Figure 3c).…”

Design of a High-Efficiency and -Gain Antenna Using Novel Low-Loss, Temperature-Stable Li2Ti1–x(Cu1/3Nb2/3)xO3 Microwave Dielectric Ceramics

“…(The schematics of the crystal structure are displayed in Figure b). As a consequence, a continuous solid solution with a rock-salt-type structure is formed in the LTCN x (0 ≤ x ≤ 0.4) system, which is similar to the other reports. ,− To get a clear understanding of the correlation between the lattice parameters and the x value of LTCN x ceramics, refinements were carried out by GSAS software based on the XRD patterns, which were collected from LTCN x (0 ≤ x ≤ 0.4) ceramic powders. Monoclinic ( C 2/ c ) and cubic ( Fm 3̅ m ) Li 2 TiO 3 were taken as starting models of LTCN x (0 ≤ x ≤ 0.2) and LTCN x (0.3 ≤ x ≤ 0.4) for Rietveld refinement, respectively. , The observed and calculated XRD patterns are displayed in Figure d–h.…”