Novel, Low Cost t'- and m'-Zirconia Ceramics for a Storage Heater

The objective of this work is to determine the best possible polycrystalline zirconia from the standpoint of properties and cost for applications in storage heaters. Our prior work has shown that highly stable tetragonal t'-zirconia with domain structure containing (= 8 mol.% yttria. The excellent properties of t'- and m'-zirconia and stabilizers are the result of their domain structure. A survey of availbale zirconia and stabilizers will be conducted to identify suitable materials from the standpoint of cost. For the determination of optimum composition, samples with yttria content between 0 and 20 mol.% will be fabricated by heat treating at temeparures >= 2000 C. Creep resistance, erosion resistance, thermal shock resistance, strength, toughness, stability at low (200 to 600 C) and high (approx 1600 C) temperatures, and thermal conductivity of conventional tetragonal, highly stable t'-zirconia, shatter-proof m'-zirconia, and cubic zirconia will be measured. This information will be used to identify the most optimum yttria content and processing conditions of zirconia for storage heater applications. It is anticipated that t'-materials with yttria content <= 3 mol.% and m'-materials with no yttria will be the best materials, both from the standpoint of properties and cost.