Rapid processes for the production of nanocrystal yttria-stabilized tetragonal zirconia polycrystalline ceramics: ultrasonic spray pyrolysis synthesis and high-frequency induction sintering

Abstract

In this study, nanocrystalline 3 mol % yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic was produced by sintering with a high-frequency induction heating (HFIH) system of granular powders obtained by ultrasonic spray pyrolysis (USP) at 600 °C. The granular nano-sized powders (10-30 nm) were micron in size (average size: 700 nm), spherical in shape and amorphous. The influences of the HFIH sintering temperature (1400-1600 °C), applied current time (60-300 sec.) and the mechanical pressure (10 MPa and 20 MPa) on the final density and grain size of the products were investigated. The amorphous granular Y-TZP powders compressed with the HFIH system allow very rapid condensation in the tetragonal phase at high density and avoid grain growth. High density (relative density over 95) nanocrystalline Y-TZP ceramic with ∼70 nm size could be obtained from the simultaneous application of 20 MPa pressure and an induced current within 300 sec. of sintering time at 1500 °C. In this condition, the sample’s maximum hardness and fracture toughness values were reached at 14.9 GPa and 3.8 MPa·m1/2, respectively. Y-TZP powders produced in nano-micro structure with the USP system were sintered with the HFIH system and rapid production was achieved by preventing grain growth.