Ceramic heaters are generally known in the art. Normally, a ceramic heater will include an insulating portion, a heat generating portion, and electrical lead portions formed integrally with a ceramic body or substrate. The heater element and lead portions are normally formed of a single electrically conductive metal such as an inexpensive non-noble or base metal such as tungsten and molybdenum. However, the heater element and lead portions made of such metals are prone to oxidize during long periods of use at high operating temperatures in oxidizing atmospheres such as air. The oxidation may result in disconnection of the heat-generating portion of the ceramic heater and, thus, heater failure.
The art has sought to solve this problem by decreasing the amount of non-noble or base metal used in the ceramic heater. For example, U.S. Pat. No. 4,952,903 to Shibata et al., (hereinafter "Shibata") teaches a ceramic heater including a ceramic body and a heater element formed of a cermet containing a ceramic material and a metal material which principally consists of at least one noble metal; and, including electrical lead portions formed of a metallic material consisting of at least one base metal or formed of a cermet containing ceramic material and metallic material. Shibata mentions the making of the heater element from a noble metal such as platinum or rhodium, but dismisses such use because of costs and the difficulty of bonding a noble metal to a ceramic substrate. The use of such noble metal would overcome the problems associated with oxidation of the metal. Thus, an economic and practical means of using such noble metals would be advantageous to the art of ceramic heaters. For these reasons, there remains room for improvement in the art.