Material composition having core-shell microstructure used for varistor

A method for manufacturing a single-layered or multiple-layered varistor comprising a sintered ceramic body having an adjustably designated voltage, comprising steps of:

• a) selecting surge absorbing ceramic powders as raw material, each of said ceramic powders contains a crystalline core-shell microstructure comprising a grain having a predetermined size constructed as a cored-structure made of a sintered conductive or semi-conductive material and a layer of glass having a predetermined thickness constructed as a shelled-structure covered over the cored-structure;
• b) mixing said ceramic powders with appropriate binder, dispersant, plasticizer and organic solvent to form a slurry;
• c) producing green tape(s) made of the slurry through a given doctor blade casting;
• d) stacking a predetermined number of green tape(s) having an inner electrode layer printed thereon in an manner that ends of the inner electrodes alternately appear;
• e) allowing the stacked green tape(s) sintered as a ceramic body at a temperature between 600° C. and 1,100° C., and
• f) the sintered ceramic body having a designated breakdown voltage executed at step a) by precisely controlling either the size of the grain of the cored-structure or the thickness of the glass layer of the shelled-structure of the surge absorbing ceramic powders, or further executed at step c) by precisely controlling each green tape having a thickness ranged between 15 μm and 200 μm.