Dielectric Energy Storage Density Research Articles

Enhanced piezoelectric, electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics

The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30 kV/cm. The piezoelectric property shows good thermal stability due to high depolarization temperature (Td). For BNKT20, a large low electric field-induced strain of 0.36% is obtained at 120 °C under 50 kV/cm, the corresponding normalized strain coefficient is up to 720 pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08 K) in BNKT20 ceramic is obtained at 50 kV/cm using indirect calculation. Above 100 °C, the dielectric energy storage density and efficiency of BNKT20 is still up to ~0.85 J/cm3 and 0.75, respectively. The BNKTx ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.

Effect of rare-earth additions on the structure and dielectric energy storage properties of BaxSr1-xTiO3-based barium boronaluminosilicate glass-ceramics

BaxSr1-xTiO3-based barium boroaluminosilicate (BST-BBAS) glass-ceramics added with La2O3, Gd2O3 and Yb2O3 were fabricated through the melting method followed by controlled crystallization, respectively. The X-ray diffraction and the field emission scanning electron microscopy were investigated the phase composition and microstructure for the BST-BBAS glass-ceramics added with rare-earth additions, then the temperature-dependent dielectric properties and the voltage-withstand measurements were applied to study the effect of rare-earth additions on the dielectric energy storage density. These results show that the certain content of rare-earth additions can optimize the microstructure and phase structure effectively. And with the decrease of ionic radiuses of rare-earth elements, the microstructure of the glass-ceramics become more uniform. When added with 0.5 mol% Yb3+, the theoretical energy storage density of the BST-BBAS glass-ceramics gets the largest value of 3.5 J/cm3 which is about 1.8 times compared to the undoped one.

Dielectric energy storage densities in Ba 1-x Sr x Ti 1-y Zr y O 3 ceramics

This paper presents measurements of the Weiss temperature, the Curie constant, the spontaneous polarization and the stored dielectric energy density of Ba1-xSrxTi1-yZryO3 ceramics for compositions with 0≤x≤1 and 0≤y≤0.5. The first three of these dielectric parameters are used to predict the density of energy storage that can be obtained when ceramics of these compositions are used as capacitor dielectrics. These predictions are compared with direct measurements of energy densities which show that for moderate electric field strengths (-50 kV mm -1) the stored dielectric energy densities were the largest for ceramics with x>0.7 and y ∼0.2. © 2000 Kluwer Academic Publishers