The invention relates to fuel cell devices and systems, and methods of using and making fuel cell devices and systems. The fuel cell devices include an elongate ceramic substrate, such as a rectangular or tubular substrate, the length of which is the greatest dimension such that thermal expansion is exhibited along a dominant axis that is coextensive with the length. A reaction zone is positioned along a first portion of the length for heating to an operating reaction temperature, and at least one cold zone is positioned along a second portion of the length for operating at a temperature below the operating reaction temperature. There are one or more fuel passages and one or more oxidizer passages extending within an interior solid support structure of the elongate substrate, each having an associated anode and cathode, respectively, which are separated by an electrolyte. The passages include a neck-down point.