Method of manufacturing a metal-oxide varistor with improved energy absorption capability

A method of manufacturing a cylindrical metal-oxide varistor with improved energy absorption capability, wherein electrodes are arranged making contact with end surfaces of the metal-oxide varistor, the end surfaces of the varistor are coated with metal, and an envelope surface is supplied with a high-resistance material so as to form a zone with enhanced resistivity close to the envelope surface, the method comprising:

• forming a metal-oxide powder into an unsintered cylindrical varistor body;
• coating envelope surfaces of the unsintered varistor body with an aqueous dispersion of a high-resistance material comprising SiO2, LiO2 or Cr2O3 by spraying, dip-painting, rolling, or spray painting;
• and
• sintering the coated varistor body at 1100-1300° C. for 2-10 hours, wherein during the sintering the high-resistance material diffuses into the surface zone of the envelope surface of the metal-oxide varistor to a depth of 2-6 mm.