HAFNIA-RICH MIXED OXIDE CERAMICS OF THE SYSTEM Hf02-Zr02-Ti02 FOR HEATERS AND HEAT EXCHANGERS IN ELECTROTHERMAL THRUSTERS The Effects of Titania on Selected Electrical and Mechanical Properties of Hafnia-Rich Mixes Oxides in the System Hafnia-Zirconia-Titania

摘要

A study of the effects of titania on selected properties of hafnia-rich mixed oxides in the system hafnia-zirconia-titania (HZT) was made in the region 5 to 20 mol% titania. The studied properties included electrical conductivity, thermal expansion, and fracture strength and toughness. The electrical conductivity was measured using a two-point probe with 10 kHz ac current on bars over the temperature range 400 to 1700°C and oxygen partial pressure range 10-31 to 21 kPa (10-33 to 0.21 atm). The thermal expansion was measured using a dilatometer from room temperature to 1700°C. Fracture strengths were determined using a four-point bend fixture on nonindented bars at room temperature and on triple Vickers indented bars at room temperature, 1000°C, and 1400°C. Fracture toughness (Kic) values were also determined from the indented bars.