Ceramic heater, glow plug using the same, and method for manufacturing the same

A ceramic heater (1) comprising:

• a rod-shaped heater body (2) having a ceramic resistor (10), which is formed of an electrically conductive ceramic, embedded in a ceramic substrate (13), which is formed of an insulating ceramic,
• wherein the ceramic resistor (10) has a first resistor portion (11) that is disposed at a front end portion of the heater body (2) and is formed of a first electrically conductive ceramic, and second resistor portions (12) that are disposed on a rear side of the first resistor portion (11) so as to extend along a direction of an axis (O) of the heater body (2), each of the second resistor portions (12) having a front end part joined to an end part of the first resistor portion (11) and being formed of a second electrically conductive ceramic, the second electrically conductive ceramic having an electrical resistivity that is lower than an electrical resistivity of the first electrically conductive ceramic, and
• wherein at least a portion of a joint interface (15) between the first resistor portion (11) and each of the second resistor portions (12) deviates from a transverse plane (P) perpendicularly intersecting the axis (O) of the heater body (2), and the joint interface (15) includes one of a plane (15t, 15e, 15d), a curved surface (15c), and a combination thereof (15c, 15d) perpendicularly intersecting a reference plane (K) that is coincident with the axis (O) of the heater body (2) and an axis (J) of the corresponding second resistor portion (12).