Abstract: This invention provides a humidity sensor having a negative coefficient of resistivity for relative humidity, which comprises 99.99 to 10 mole percent of iron oxide (Fe.sub.2 O.sub.3) and 0.01 to 90 mole percent of at least one member selected from alkali metal oxides, which are lithium oxide (Li.sub.2 O), sodium oxide (Na.sub.2 O), potassium oxide (K.sub.2 O) and cesium oxide (Cs.sub.2 O). The amount of the alkali metal oxide in the sensor is preferably 0.01 to 25 mole percent. This sensor is advantageous because it can accurately detect the changes in humidity and it has a long, stable life.

Abstract: A voltage-dependent resistor comprising a sintered body consisting essentially of ZnO, as a main constituent, and, as additives, bismuth oxide (Bi.sub.2 O.sub.3), titanium oxide (TiO.sub.2) and one or two members selected from the group consisting of aluminum fluoride (AlF.sub.3), chromium fluoride (CrF.sub.3), nickel fluoride (NiF.sub.2) and strontium oxide (SrO) with electrodes applied to the opposite surfaces of the sintered body. This voltage-dependent resistor has a low C-value, a high n-value and a high power dissipation for surge energy and high stability to a high D.C. load. Other additives such as cobalt oxide (CoO), manganese oxide (MnO), barium oxide (BaO), boron oxide (B.sub.2 O.sub.3), chromium oxide (Cr.sub.2 O.sub.3), nickel oxide (NiO) and germanium oxide (GeO.sub.2) improve the voltage nonlinear property of the sintered body.

Abstract: A voltage-dependent resistor comprising a sintered body consisting essentially of ZnO, as a main constituent, and, as additives, bismuth oxide (Bi.sub.2 O.sub.3), cobalt oxide (CoO) and/or manganese oxide (MnO) and/or aluminum oxide (Al.sub.2 O.sub.3) and gallium oxide (Ga.sub.2 O.sub.3) and/or indium oxide (In.sub.2 O.sub.3) with electrodes applied to the opposite surfaces of the sintered body. This voltage-dependent resistor has a low C-value, a high n-value, high power dissipation for surge energy and a high stability to a high D.C. load. Other additives such as titanium oxide (TiO.sub.2), chromium oxide (Cr.sub.2 O.sub.3) and nickel oxide (NiO) improve the voltage dependent property of the sintered body.

Abstract: A voltage-dependent resistor comprising a sintered body comprising ZnO as a major part and Bi.sub.2 O.sub.3 and GeO.sub.2 as additives with electrodes applied to the opposite surfaces of the sintered body. This voltage-dependent resistor has a low C-value and a high n-value in I=(V/C).sup.n along with high power dissipation for surge energy and high stability to a high D.C. load. Further, other additives such as NiO, Co.sub.2 O.sub.3, MnO, TiO.sub.2 and Cr.sub.2 O.sub.3 can advantageously be added to the sintered body.