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. 2019 Apr 27;12(9):1370.
doi: 10.3390/ma12091370.

Temperature Stable Cold Sintered (Bi 0.95 Li 0.05)(V 0.9 Mo 0.1)O 4-Na 2 Mo 2 O 7 Microwave Dielectric Composites

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Temperature Stable Cold Sintered (Bi 0.95 Li 0.05)(V 0.9 Mo 0.1)O 4-Na 2 Mo 2 O 7 Microwave Dielectric Composites

Dawei Wang et al. Materials (Basel). .
Free PMC article

Abstract

Dense (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 (100-x) wt.% (Bi0.95Li0.05)(V0.9Mo0.1)O4 (BLVMO)-x wt.% Na2Mo2O7 (NMO) composite ceramics were successfully fabricated through cold sintering at 150 °C under at 200 MPa for 30 min. X-ray diffraction, back-scattered scanning electron microscopy, and Raman spectroscopy not only corroborated the coexistence of BLVMO and NMO phases in all samples, but also the absence of parasitic phases and interdiffusion. With increasing NMO concentration, the relative pemittivity (εr) and the Temperature Coefficient of resonant Frequency (TCF) decreased, whereas the Microwave Quality Factor (Qf) increased. Near-zero TCF was measured for BLVMO-20wt.%NMO composites which exhibited εr ~ 40 and Qf ~ 4000 GHz. Finally, a dielectric Graded Radial INdex (GRIN) lens was simulated using the range of εr in the BLVMO-NMO system, which predicted a 70% aperture efficiency at 26 GHz, ideal for 5G applications.

Keywords: cold sintering process; graded radial index lens; microwave dielectric ceramics.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Bulk and relative densities of (100−x) wt.% (Bi0.95Li0.05)(V0.9Mo0.1)O4 (BLVMO)-x wt.% Na2Mo2O7 (NMO) ceramic composites.
Figure 2
Figure 2
X-ray diffraction (XRD) patterns of (100−x) wt.% BLVMO-x wt.% NMO ceramic composites.
Figure 3
Figure 3
Raman spectra of (100−x) wt.% BLVMO-x wt.% NMO ceramic composites.
Figure 4
Figure 4
The SEM and BSE images of (a) conventionally-sintered BLVMO, (b) cold-sintered NMO, and (c,d) cold-sintered BLVMO-20 wt.% NMO samples.
Figure 5
Figure 5
The microwave properties of (100−x) wt.% BLVMO-x wt.% NMO ceramic composites as a function of x (NMO fraction). (a) Qf, (b) TCF, (c) εr.
Figure 6
Figure 6
(a) Lens design principle; (b) Simulated electric field of a ceramic Graded Radial INdex (GRIN) lens that transforming spherical wavefronts into a planar wavefront at 26 GHz.
Figure 7
Figure 7
Simulated far-field radiation patterns of the ceramic GRIN lens at 26 GHz.

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