Influence of test procedure on dielectric breakdown strength of alumina

Abstract

Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV•mm -1 were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations (< 2 kV•mm -1 ) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization.

Microstructure, phase and dielectric strength of thermally sprayed alumina layers in coating‐based heating systems

“…Consequently, the ratio of the breakdown voltage (V) to the coating thickness (μm) was calculated, which is also known as the dielectric strength (V/μm). The dielectric strength is defined as the potential gradient at which the dielectric breakdown occurs 35 . It should be mentioned that the theoretic dielectric strength of a material is intrinsic, and it is independent of its thickness and configuration 36 .…”

Effect of sintering temperature in argon atmosphere on microstructure and properties of 3D printed alumina ceramic cores

“…According to Zhu et al [53], the flexural strength of porous alumina increased with increasing sintering temperature. The flexural strength of porous ceramics depends on the sintering neck areas among the grains and the amount of sintering necks [54][55][56]. Along with the increase in sintering temperature, the growth of sintering necks and sintering densification are promoted, increasing the flexural strength and decreasing the porosity.…”

Description of the statistical variations of the measured strength for brittle ceramics: A comparison between two-parameter Weibull distribution and normal distribution

“…2 in describing the strength variations in the measured strength of real materials [9][10][11][12]. Weibull function was also used to describe the statis-tical characteristics of other properties, such as hardness [13], fracture toughness [13][14][15], dielectric breakdown strength [16,17], subcritical crack growth [18], etc. Note that it is impossible to know the true values of the Weibull parameters for a given material and analyses of the experimentally measured strength data according to Eq.…”