What type of metal is used for the semiconductor blocks in a lightning arrestor?

The correct choice is zinc oxide material. In lightning arrestors, semiconductor blocks are designed to effectively manage electrical surges and protect electrical systems from damage caused by lightning strikes. Zinc oxide is used in these applications due to its excellent semiconductor properties, allowing it to conduct electricity under certain conditions while also providing high resistance under normal conditions. This characteristic makes it particularly suitable for diverting excess voltage away from sensitive equipment, thereby enhancing safety and reliability.

Zinc oxide's ability to maintain performance over a wide range of temperatures and its reliability over long periods further contribute to its effectiveness in lightning arrestors. Other metals like aluminum, copper, and silver, while useful in various electrical applications, do not possess the same semiconductor properties and, therefore, are not suitable for this specific function in a lightning arrestor. Their primary roles are more aligned with conduction and structural support rather than controlling voltage surges.