Glass-ceramic, process for preparing a glass-ceramic and use of a glass ceramic

The glass-ceramic comprising a vitreous phase and a crystalline phase, the crystalline phase ferroelectric crystallites having a maximum diameter of 20 to 100 nm and with a content of the glass-ceramic of> 50 Vol .-% by weight. Furthermore, no or a proportion of the glass ceramic of ≦ 10 vol .-% of non-ferroelectric crystallites on, the crystalline phase. In addition, the glass ceramic has no or ≦ 0.01 vol .-% of pores, and the value of e '· V is produced the glass ceramic by first preparing a starting glass and this is then ceramified with at least one heating or cooling rate of greater than 10 K / min to give the glass-ceramic.