Creep Behavior of Zirconia Foams Used in Electrical Furnaces (2100 K - Air)

s Some zirconia foams are used as heating elemeht in electrical furnaces. Their creep behaviour has been investigated at high temperature and under low stress. Important visco-elastic behaviour has been observed. It is likely due to recrystallization, which is sensitive to the tetragonal-cubic phase transition and to the stress. I INTRODUCTION Porous and dense zirconia based ceramics have been used for several years as heating element in electrical furnace /I/. The so-called zirconia furnace can be operated in air at 2100 X, for long periodes. The aim of the present study is to investigate the treep behaviour of some new zirconia porous ceramics, such as zirconia foams ( ) which are suitable as heating element. During the seventies, large grain dense ceramics (called ZGM) were used. More recently, porous ceramics made in Japan were prefered according to their thermal shock resistance, but their rough and inhomogeneous microstructure enhanced their brittleness. New materials were made by foam processing. They are much more homogeneous. The porosity lies in the range 0.25 0.71, so that it is very convenient to choose the electrical resistance and the thermal conductivity of the different parts of the heater (usually, three parts). II ELECTRICAL RESISTANCE First of all, the electrical resistance of the zirconia foams was measured to check that they can be used as heater. The sample was an hollow cylinder: 20 mm inner 1 ( ) Produced by Ceramiques Techniques Desmarquest. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986199