What makes Tantalum (Ta) special as an anode is the dielectric oxide which is electrolytically formed on the metal. Tantalum Pentoxide can be grown in extremely low thickness with very high voltage withstanding capability. The volumetric efficiency of a dielectric is the product of the permittivity constant and the dielectric constant divided by the dielectric thickness squared. Thus, despite it’s relatively low dielectric constant of 27, Tantalum capacitors exhibit high volumetric efficiency due to the extremely thin and uniform dielectric which provides excellent voltage withstanding capability. When compared to ceramic capacitors, the dielectric thickness of Tantalum is thinner for the same voltage ratings.