Internal-strain-controlled tungsten bronze structural ceramics for 5G millimeter-wave metamaterials

Miniaturization, power dissipation and temperature stability are the most critical factors restricting the microwave use of ceramic-based devices. Balancing them, especially for the ceramics with high dielectric constant, is a great challenge. Herein, a new strategy by trivalent ion (Al3+ and Ga3+) co-substitution is put forward in tungsten bronze structural Ba4Nd9.33Ti18O54 ceramics for millimeter-wave metamaterials, and a nearly 40% increase in Q(f) values with stable temperature characteristics is obtained. The crystal symmetry, morphology and the vibration modes are characterized by XRD, EDS and Raman spectroscopy, suggesting the varied internal strain and oxygen octahedron tilt from the mismatch of different cations. The best performance of Ba4Nd9.33Ti18-x(Al0.4Ga0.6)(x)O54-0.5x (BNT-AG(x)) is observed when x is 2.4: epsilon(r) = 67.71, Q(f) = 13 675 GHz, tau(f) = +4.4 ppm degrees C-1. Considering the dispersion relationship of BNT-AG(x) ceramics further, the structure of BNT-AG(x) metamaterials is uniquely designed, and the sub-wavelength BNT-AG(x) blocks are also fabricated to demonstrate the frequency selection filtering function with high temperature stability at the millimeter-wave band (>30 GHz), which is of great significance to achieve some eMBB (Enhanced Mobile Broadband) scenes of 5G (the 5th Generation) technology, from a metal loaded cavity to free space.

Automated summary

A novel strategy of trivalent ion (Al3+ and Ga3+) co-substitution in tungsten bronze structural Ba4Nd9.33Ti18O54 ceramics for millimeter-wave metamaterials is proposed in this study. The results show a significant increase in Q(f) values and effective balance of miniaturization, power dissipation, and temperature stability under stable temperature characteristics.