Abstract

Low-loss tungsten-bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation (5G) communication technology. In this work, a novel Al/Nd co-doping method of Ba4Nd9.33Ti18O54 (BNT) ceramics with a chemical formula of Ba4Nd9.33+z/3Ti18−zAlzO54 (BNT-AN, 0 ⩽ z ⩽ 2) was proposed to improve the dielectric properties through structural and defect modulation. Together with Al-doped ceramics (Ba4Nd9.33Ti18−zAl4z/3O54, BNT-A, 0 ⩽ z ⩽ 2) for comparison, the ceramics were prepared by a solid state method. It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping. As the doping amount z increased, the relative dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) of the ceramics decreased, and the Q×f values of the ceramics obviously increased when z ⩽ 1.5. Excellent microwave dielectric properties of εr = 72.2, Q×f = 16,480 GHz, and τf = +14.3 ppm/°C were achieved in BNT-AN ceramics with z = 1.25. Raman spectroscopy and thermally stimulated depolarization current (TSDC) technique were firstly combined to analyze the structures and defects in microwave dielectric ceramics. It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies ({rm{V}}_{rm{O}}^{ cdot cdot }), demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.

Highlights

  • Nowadays, the fifth-generation (5G) telecommunication technology has been developing rapidly, in which ceramic materials could play important roles [1]

  • A new strategy, i.e., Al/Nd co-doping in BNT ceramics, is proposed to improve the dielectric properties of tungsten–bronze microwave dielectric ceramics through structural and defect modulation, in which the condition of charge balance was maintained by using the same amount of Al3+ to substitute Ti4+ and adding Nd3+ to fill the vacancies at the A1 site simultaneously, with a chemical formula of Ba4Nd9.33+z/3Ti18−zAlzO54 (BNT–AN, 0 ≤ z ≤ 2)

  • Microwave dielectric ceramics with better comprehensive performance are obtained through Al/Nd co-doping, and the relationship between the structure and the microwave dielectric properties of the ceramics is discussed in the present paper

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Summary

Introduction

The fifth-generation (5G) telecommunication technology has been developing rapidly, in which ceramic materials could play important roles [1]. To further improve the Q×f values of BLT ceramics, a large amount of doping modification research was displayed, especially the substitution of low-valence cations for Ti4+ at the B sites. In order to meet the condition of charge balance, one method was to use composite ions such as (Cr1/2Nb1/2)4+, (Mg1/3Nb2/3)4+, or (Al1/2Nb1/2)4+ to substitute Ti4+ [31,32,33], yet it complicated the synthesis process. A new strategy, i.e., Al/Nd co-doping in BNT ceramics, is proposed to improve the dielectric properties of tungsten–bronze microwave dielectric ceramics through structural and defect modulation, in which the condition of charge balance was maintained by using the same amount of Al3+ to substitute Ti4+ and adding Nd3+ to fill the vacancies at the A1 site simultaneously, with a chemical formula of Ba4Nd9.33+z/3Ti18−zAlzO54 (BNT–AN, 0 ≤ z ≤ 2). Microwave dielectric ceramics with better comprehensive performance are obtained through Al/Nd co-doping, and the relationship between the structure and the microwave dielectric properties of the ceramics is discussed in the present paper

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