The Effect of Interfacial Polarization on the Energy Density of Ferroelectric Glass-Ceramics

In the last two years, the US Naval Research Laboratory has been able to synthesize barium strontium titanate (BST)-based glass-ceramics with dielectric breakdown strength as high as 800 kV/cm and dielectric constant up to 1200. Unfortunately, the energy density of the candidate glass-ceramics was only ~1 joule/cc when measured using a discharge measurement circuit. Polarization-electric field measurements revealed wide open hysteresis loops, indicating that most of the electrical energy was not released during discharge. Subsequent experiments showed that the buildup of interfacial polarization was the likely cause in this composite dielectric system. Using the Maxwell-Wagner capacitor model, we were able to quantify the dielectric response of composites based on the permittivities and conductivities of the constituent phases. The response was used to plot polarization-electric field hysteresis for energy density predictions. The results indicated that the aluminosilicate glass phase is the major contributor to the interfacial polarization in this glass-ceramic system.