Effect of microstructure on lifetime performance of barium titanate ceramics under DC electric field loading

Bulk barium titanate (BaTiO3) ceramic specimens with various amounts of abnormal grains are prepared. A direct current (DC) electric field of 6 MV m−1 is applied to the specimens and their lifetimes are evaluated. Comparing to the specimens with only small normal grains, the time to failure of the specimens with coarse abnormal grains is significantly shorter. It is found that the BaTiO3 specimens would fail within 200 h when abnormal grains are present in the microstructure. However, the lifetimes of the specimens containing abnormal grains vary significantly from one to another. The Weibull statistics is adopted to estimate the extent of data scatter. The statistical analysis indicates that the amount of abnormal grains has little influence on the lifetime performance of bulk BaTiO3 ceramics under large DC electric fields. In most of the failed BaTiO3 specimens, regardless of their lifetimes, large through-thickness round holes with recrystallization features are present. A mixed failure mode consisting of avalanche and thermal breakdowns is observed for the failed specimens.