Process of producing a glass-ceramic, the glass-ceramic made therby and its uses

A process for producing a glass-ceramic, said glass-ceramic comprising not more than 10% by volume of non-ferroelectric crystallites and at least 50% by volume of ferroelectric crystallites, said ferroelectric crystallites having a maximum diameter of 20 to 100 nm, wherein said glass-ceramic has not more than 0.01% by volume of pores and e′·V2max of said glass-ceramic has a value of at least 20 (MV/cm)2, wherein e′ is a dielectric constant of the glass-ceramic at 1 kHz and Vmax is a breakdown voltage per unit thickness of the glass-ceramic, said process comprising the steps of:

• a) producing a starting glass;
• b) ceramicizing the starting glass at a heating rate of at least 10 K/min during the ceramicizing to form the glass-ceramic;
• and
• c) heating at said heating rate of said at least 10 K/min by means of infrared radiation at a color temperature of greater than 1500° C. during the ceramicizing;
• whereby said glass-ceramic is obtained with not more than 10% by volume of said non-ferroelectric crystallites and at least 50% by volume of said ferroelectric crystallites having said maximum diameter of 20 to 100 nm and said glass-ceramic has not more than 0.01% by volume of said pores and has said value of said e′·V2max of said glass-ceramic.