Enhancing Comprehensive Energy Storage Properties in Tungsten Bronze Sr0.53Ba0.47Nb2O6-Based Lead-free Ceramics by B-Site Doping and Relaxor Tuning

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors of next-generation pulse devices. Herein, a lead-free Sb-modified (Sr0.515Ba0.47Gd0.01) (Nb1.9-xTa0.1Sbx)O-6 (SBGNT-based) tungsten bronze ceramic is designed and fabricated for high-density energy storage capacitors. Using a B-site engineering strategy to enhance the relaxor characteristics, Sb incorporation could induce the structural distortion of the polar unit BO6 and order-disorder distribution of B-site cations as well as the modulation of polarization in the SBGNT-based tungsten bronze ceramic. More importantly, benefiting from the effective inhibition of abnormal growth of non-equiaxed grains, Sb introduction into SBGNT-based ceramics could effectively suppress the conductivity and leakage current density, enhancing the breakdown strength, as proved by the electrical impedance spectra. Consequently, a remarkable comprehensive performance via balancing recoverable energy density (similar to 3.26 J/cm(3)) and efficiency (91.95%) is realized simultaneously at 380 kV/cm, which surpasses that of the pristine sample without the Sb dopant (2.75 J/cm(3) and 80.5%, respectively). The corresponding ceramics display superior stability in terms of fatigue (10(5) cycles), frequency (1 similar to 200 Hz), and temperature (20 similar to 140 degrees C). Further charge-discharge analysis indicates that a high power density (89.57 MW/cm(3)) and an impressive current density (1194.27 A/cm(2)) at 150 kV/cm are achieved simultaneously. All of the results demonstrate that the tungsten bronze relaxors are indeed gratifying lead-free candidate materials for dielectric energy storage applications.

Automated summary

In this study, a lead-free Sb-modified tungsten bronze ceramic was designed and fabricated to enhance the relaxor characteristics. The incorporation of Sb induced structural distortion and order-disorder distribution, resulting in improved breakdown strength and remarkable energy storage performance at high power and current density.