Achieving high permittivity and ultralow dielectric loss in tungsten-bronze-type Ba4(Sm1-x-yBixNdy)9.333Ti18O54 ceramics by Nd/Bi co-substitution on A-site

The tungsten-bronze-type Ba 6-3x Sm 8+2x Ti 18 O 54 ceramic materials exhibit fantastic application potential in electronic devices owing to their superior microwave dielectric properties. However, the huge challenge of realizing high dielectric constant accompanied by ultralow dielectric loss still exists and has become a critical bottleneck impeding the operation of multilayer ceramic capacitors (MLCCs) and capacitive voltage dividers in the low-frequency range. Herein, we report high dielectric constant and ultralow dielectric loss performance of Ba 4 (Sm 1-x-y Bi x Nd y ) 9.333 Ti 18 O 54 (0.3≤x ≤ 0.4, 0.1≤y ≤ 0.2) ceramics via A-site modification strategy of Bi/Nd co-substitution. A high dielectric constant of 115 and ultralow loss tangent of 0.003 at 1 kHz are achieved simultaneously in Ba 4 (Sm 1-x-y Bi x Nd y ) 9.333 Ti 18 O 54 ceramics with x = 0.4 and y = 0.2. Incorporating an appropriate amount of Bi 3+ ions contributes to enhancing the dielectric polarizability of the crystal lattice, and greatly strengthening the sintering ability of ceramics as well as local distortion characteristics, leading to an improvement in the dielectric constant and ultimately a deterioration in the loss tangent, which is confirmed by XRD, Raman, SEM and Impedance spectroscopy. The Bi/Nd co-substitution has a significant impact on further improving the dielectric constant, and the compensation of the loss tangent value mainly is derived from the conduction loss with the reduction of leakage currents. Moreover, the high recoverable energy density of 1.2 J/cm 3 and energy efficiency of 87%, as well as excellent temperature (25∼180 °C) and frequency (1∼140 Hz) stability, are obtained in this ceramic owing to high breakdown strength via A-site modification strategy of Bi/Nd co-substitution. These findings establish an effective strategy of Bi/Nd co-substitution to develop highly reliable Ba 4 Sm 9.333 Ti 18 O 54 ceramics, opening a new path for creating next-generation dielectric materials tailored for stable energy storage in high-voltage, low-frequency electronics.