A Brilliant Idea behind Every Product.
A Brilliant Idea behind Every Product.
Applying a high voltage to a ceramic material in vacuum causes an electron avalanche. In the worst case, this can damage the ceramic. Electrical breakthrough of the ceramic can occur. The vacuum is lost and the system becomes unusable.
A coating on the inner ceramic surface „CERaconduct“ (GREEN)– a development of alumina Systems – conducts the electrons. No electron avalanche occurs. The ceramic is permanently vacuum-tight.
Ceramic materials such as alumina oxide (Al₂O₃) have been a key component of high-voltage insulators for decades. Their high dielectric strength, thermal stability, and suitability for vacuum applications make them the first choice for demanding applications. However, practical experience shows that even high-quality ceramic components can fail prematurely, especially under high voltage in vacuum.
Applications with direct current or low frequencies are particularly critical when long insulation distances are involved. Electrons being knocked out by adjacent metal parts create electrical charges on ceramic surfaces that cannot dissipate in a controlled manner. This results in unstable electrical states that compromise the safety and lifespan of the entire system.
In vacuum, high electric fields act directly on the surfaces of the materials used. Electrons are ejected from metal or ceramic surfaces and accelerated by the electric field. When these electrons hit the ceramic surface, they knock out further electrons.
This effect is described by the secondary electron emission coefficient (SEEC). For ceramic materials, this value is typically greater than one – meaning that each electron impact generates more than one additional electron. The process is self-reinforcing and leads to an electron avalanche along the ceramic surface
The effects of these electron avalanches are serious. Local charge accumulations, known as charge nests, form on the ceramic surface. Simultaneously, arcing can occur between the ceramic and adjacent metallic components.
Unstable operation and unplanned plant shutdowns in the worst case leading to complete failure of the component and loss of vacuum.
The key to avoiding these effects lies not in increasing material thickness or insulation, but in the targeted control of surface charges. This is precisely where CeraConduct from Alumina Systems comes in.
CeraConduct is a specially developed ceramic functional coating with a layer thickness of less than 1 µm. It has high resistivity but a defined low electrical conductivity. This allows free electrons on the ceramic surface to be continuously and controllably dissipated before they can accumulate and trigger critical effects.
of the ceramic surface. Electrons are no longer stored locally, but flow away in a controlled manner. Electron avalanches, charge nests, and arcing are effectively suppressed, while the insulating properties of the ceramic base material are fully retained.
The result is a significantly increased electrical stability of the component – even at high voltages in vacuum and under demanding operating conditions.
CeraConduct was specifically developed for use in highly sensitive vacuum applications:
These properties make CeraConduct a reliable solution for long-term stable high-voltage applications.
CeraConduct is used wherever ceramic insulators need to function reliably under high voltage in vacuum, including in:
With CeraConduct, Alumina Systems offers not just a coating, but a practical solution for one of the key challenges of ceramic high-voltage insulators. The result is increased operational reliability, longer service life, and reduced overall costs – from development to operation.