Capacitors are passive electrical components that store energy in the form of an electrostatic field in the dielectric material between metal contacts. They are commonly used to buffer, stabilize or couple the voltage and power flow in electric power conversion systems. High voltage capacitors are becoming increasingly required; for example in Excimer Lasers for industrial and medical applications, for medical x-ray equipment, for high voltage power supplies (HVPS) for industrial applications, and for grids for renewable energy.
Higher voltages and current densities, however, lead to an increasing thermal load. Current capacitor technologies for high power applications are mostly based on polypropylene (PP) or N4700 ceramic. Both are limited to temperatures below 90° C due to either their loss of capacitance (N4700) or their loss of reliability (PP) with rising temperatures. SCHOTT’s new class of POWERAMIC™ materials shows a superior performance regarding energy storage density and dielectric properties in an expanded temperature range.
“POWERAMIC™ glass-ceramics are highly homogenous and pore free which supports their high dielectric breakdown strength and leads to storage density exceeding that of current capacitor solutions by a factor of up to ten. It allows the construction of smaller and lighter weight capacitors,” says Dr. Martin Letz, Senior Principal Scientist at SCHOTT Research & Technology Development. “The nano-sized crystalline structure of POWERAMICTM glass-ceramics, which is tightly controlled in a truly amorphous glassy phase, improves the dielectric properties at higher field strength and expands the temperature range compared to ceramic capacitors,” he adds.
SCHOTT has more than 40 years of experience in developing and producing glass-ceramics and is a world leading supplier for a number of products such as ZERODUR® glass-ceramic with a virtually zero thermal expansion used for mirror substrates in astronomic telescopes, CERAN® glass-ceramic cooktop panels, ROBAX® glass-ceramic viewing panels for fireplaces and NEXTREMA® glass-ceramic for extreme industrial applications. By applying the same production method to a different chemical composition, SCHOTT created a new class of high performance dielectrics.
POWERAMIC™ glass-ceramics are titanate-based. As glass-ceramics, they are produced in a two-step process: at first, a transparent glass with a totally amorphous structure is melted and hot-formed as a solid, amorphous glass. In the second step, a well-defined time-temperature profile is applied to grow nano-sized crystals within the glass. Their unique properties are achieved by using highly specified and controlled chemical compositions and processes that allow for narrow tolerances and a reliable stable quality.
POWERAMIC™ glass-ceramic is supplied as a qualified semi-finished product for the production of capacitors, upon request also in metallised form. It can be used for all commercially available capacitor designs, e.g. doorknob/hockey puck capacitors, SLCs (single layer capacitors), SMD (surface mount device) capacitors, as well as in custom designs to individual customer specifications.
