| 摘要 |
PROBLEM TO BE SOLVED: To exhibit the excellent current limiting performance capable of sustaining high resistivity in order to cut off short-circuit current by containing ceramics represented by a specific composition formula containing V and Mg. SOLUTION: In a composition formula (V1-x Mg)2 Oy , 0.001<=X<=0.07, 2.93<=Y<=3 for representing (V, Mg)2 Oy . For example, 20.0 g of V2 O3 and 0.266 g of basic magnesium carbonate are molded after weighing and blending to be calcined for three hours at 1200 deg.C in Ar stream containing 3% H2 . This molded matter is crushed and then blended with 1.61 g of metallic Ni powder further to be cylindrical molded in 10 mm diameter and high further baked for five hours at 1500 deg.C in Ar stream containing 3% H2 . At this time, (V, Mg)2 Oy continues to display the PTC characteristics up to 230 deg.C possible by a measuring apparatus. Through these procedures, a PTC resistor can maintain the PTC resistor even in a high temperature region at several hundreds deg.C. Furthermore, when the PTC resistor is used as a current limiting element, the high resistivity can be maintained for a few seconds required for a switch to cut off a short-circuit current. |
