Heaters using silicon carbide substrates will offer a much greater range of
temperatures and longer life than the polymer heaters.  However, consider the
big picture and what are you going to heat and how high of temperature?
Polymers break down at 300C and if you want to use a heater to desorb sulfur
then at least 600C is required.

One of the big problems with any type of heating sensor systems is the thermal
expansion and high temperature reactions (oxidation).  Silicon carbide thermal
expansion (4H, 6H or 3C) is in the mid 10-6 range.  This is the high end of all
ceramic type materials and therefore more closely matches some of the metal
systems.  Selection of the metal system requires metals on the very low end of
the thermal expansion.  The primary metal systems that would work with SiC are
tungsten, WTi, WTa, and their carbides.  And we all know that W is a great
diffusion barrier for semiconductor build.  These alloys will function in the
upper temperature range or 900C.  (Ideal for solid oxide fuel cell systems,
reformers, clean energy combustion systems and high temperature thermal
processing of ceramic materials)  Of course, DARPA and NASA are looking at SiC
but using Pt and Au metal systems.  Good, but limited to temperatures above
600C.

One interesting side note is a number of studies have worked with tungsten tri-
oxide as the sensor substrate for chemical sensing of combustion gases.  This is
a great match for the SiC/WC/W/WO3 sensor system with WTa/W ohmic contacts.
This material system would be excellent for high temperature gas sensing
technology.   One of the remaining materials challenge will be to find a package
that will hold the sensor for the required life, > 10,000 hours.  This will
again require new innovations.
Rob Davis