Superior temperature‐stable dielectrics for MLCCs based on Bi_0.5Na_0.5TiO₃‐NaNbO₃ system modified by CaZrO₃

Abstract

An ultra-wide temperature stable ceramic system based on (1Àx) [0.94 (0.75Bi 0.5 Na 0.5 TiO 3 À0.25NaNbO 3 )À0.06BaTiO 3 ]ÀxCaZrO 3 (CZ100x) is developed for capacitor application in this study. All samples exhibit characteristics of pseudocubic structures in XRD patterns. With CaZrO 3 addition, the coupling effect of polar nanoregions (PNRs) is weakening, leading to greatly improved temperature stability of dielectric properties. Among all samples, the most attractive properties are obtained in the composition of CZ10 at <15% variation in dielectric permittivity spanning from À55°C to 400°C and lower than 0.02 of dielectric loss of between À60°C and 300°C, accompanied by high DC resistivity (10 7 Ω m at 300°C, calculated by fitting Jonscher's power law). Furthermore, tentative multilayer ceramic capacitors (MLCCs) composed of CZ10 dielectric and Ag:Pd (70:30) internal electrode layers were fabricated by tape casting and cofiring processes. Temperature-stable dielectric property in formation of MLCC was successfully realized, with small DC/C 25°C (<15%) and loss factor (≤ 0.02) between À55°C and 340°C. Meanwhile, CZ10-based MLCC showed temperatureinsensitive energy storage density of 0.31À0.35 J/cm 3 and high-energy efficiency of above 77% at 120 kV/cm in the range of À55 to 175°C. All of these exhibit wonderful temperature-stable dielectric properties and indicate the promising future of CZ10 dielectric as high-temperature ceramic capacitors. K E Y W O R D Scapacitor, ultra-high temperature ceramics, dielectric materials/properties

Thermally stable energy storage properties in relaxor BNT‐6BT‐modified antiferroelectric PNZST ceramics

“…When further increasing x, the two ε r peaks tend to merge into one peak, and the frequency dependence of ε r and tanδ are enhanced, indicating that the ergodic relaxor phase becomes dominant. 28 For the x = 0.2 sample, the T max around 100°C is discerned, and it is accompanied with a significant frequency dispersion which may be ascribed to the consequence of polar nanoregion (PNR) thermal evolutions. 29,30 For the x = 0.3 sample, the overall dielectric constant increased, and the peak is further depressed, leading to relatively flat curves.…”

“…For the x = 0.1 sample, the dielectric spectrum changes, but there are still two ε r peaks, and both ε r and tan δ tend to be frequency‐dependent, which indicate the suppressed antiferroelectric phase and the appearance of relaxor behavior, respectively. When further increasing x , the two ε r peaks tend to merge into one peak, and the frequency dependence of ε r and tan δ are enhanced, indicating that the ergodic relaxor phase becomes dominant . For the x = 0.2 sample, the T max around 100°C is discerned, and it is accompanied with a significant frequency dispersion which may be ascribed to the consequence of polar nanoregion (PNR) thermal evolutions .…”

“…This phenomenon can be explained by the solid solution between PNZST and BNT‐6BT, which increases the degree of lattice disorder because Na + , Bi 3+ , and Ba 2+ enter the A‐site, and Ti 4+ enters the B‐site. Moreover, such a solid solution reduces the geometry and polarizability of PNRs because of the increase in the number of random local fields, suppressing the dielectric anomaly and leading to flat curves, which is beneficial for improving the temperature stability of capacitance …”

“…Moreover, such a solid solution reduces the geometry and polarizability of PNRs because of the increase in the number of random local fields, 31,32 suppressing the dielectric anomaly and leading to flat curves, which is beneficial for improving the temperature stability of capacitance. 28 The unipolar P-E loops under the maximum electric field (E max ) and the corresponding energy storage property are shown in Figure 8A,B, respectively. As can be seen from Figure 8A, the x = 0.2 sample exhibits the largest electric field of 260 kV/cm, indicating its improved breakdown field.…”

A wide temperature insensitive piezoceramics for high‐temperature energy harvesting

“…The requirements of the HTEH device's temperature stability is consist with that of high‐temperature multilayer ceramic capacitor (HT‐MLCC) . As we all know, HT‐MLCC requires a small temperature coefficient of capacitance (TCC, TCC = Δ C / C base temp = ( C T − C base temp )/ C base temp ) to ensure stable working in a wide temperature region . Considering upper operating temperature of HT‐MLCC is more than 300°C, the base temperature was normally chosen at 150°C or 200°C .…”