REACTIVE SYNTHESIS AND SPARK PLASMA SINTERING OF GAHNITE (ZnAl₂O₄)

Zinc Aluminate Spinel, ZnAl₂O₄, which is also designated as gahnite, is a ceramic semiconductor with a band gap of about 3.9 eV and large absorbance in the UV region, thus it has emerged as an alternative choice for transparent conducting oxide when doped with transition metal ions. Polycrystalline transparent gahnite was fabricated by Spark Plasma Sintering (SPS) technique from pure oxides with and without LiF additives. The effect of the SPS parameters (temperature, heating rate and holding time) on the kinetics of gahnite synthesis during SPS treatment as well as the optical and mechanical properties of dense transparent specimens are investigated. It was established that the LiF addition significantly promotes reaction synthesis of gahnite from pure oxides and the powder densification. In-line transparency of the LiF-doped samples sintered at 1200°C for 20 min with heating rate 5 deg/min, under pressure of 60 MPa was about 72 and 78% at 600 nm and 1000 nm wave length, respectively.

Keywords: Gahnite, SPS, mechanical properties, transparency.