Hot Isostatic Pressing of Submicron La2Zr2O7 Powder Prepared by the Hydrazine Method.

Abstract

In the ZrO2-La2O3 system, metastable c-ZrO2 solid solutions (ss) containing up to ≈27 mo1% La2O3 crystallize at low temperatures from amorphous materials prepared by the hydrazine method The formation of La2Zr2O7 proceeds via two reaction processes; (i) decomposition of c-ZrO2 (ss) (c-ZrO2 (ss) → La2Zr2O7 + t-ZrO2) above 1100°C and (ii) asolid-state reaction of t-ZrO2 and La2O3 at 1200° to 1300°C. Submicron La2Zr2O7 powder is producedat 1300°C. Dense La2Zr2O7 ceramics (99. 5% of theoretical) with an average grain size of 10 μm have been fabricated by hot isostatic pressing (1500°C/2h/196MPa). Their fracture toughness and bending strength are 1. 9 MPa-m1/2 and 172 MPa, respectively. They exhibit an electrical conductivity of 1. 5x10-1 S-m-1 at 1000°C.