The Effect of Mechanical Activation on Synthesis and Properties of MgAl₂O₄ Ceramics


Magnesium aluminate, MgAl2O4 and other alumina-based spinels are ceramics with high hardness, high melting point and mechanical strenght. Spinels can also be used as dielectrics in microwave applications. The goal of this study was to examine the effects of mechanical activation and sintering temperatures on physico-chemical properties of spinel.

MgAl2O4 was produced by solid state reaction between MgO and α-Al2O3 . The starting powders were mixed by ball milling to homogenize without significant particle size reduction. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 1 h. Powders were compacted at 300 MPa. Heat treatments were performed in air, at temperatures ranging from 1200 to 1600 °C with 2 h dwell time, to determine the amount of spinel formation as a function of temperature. Phase composition and microstructure of initial powders and heated samples were determined by means of X-ray diffraction, particle size analysis, and scanning electron microscopy. The influences of milling and consolidation parameters were studied by electrical measurements and mechanical characterization.

The main conclusion of this study was that mechanical activation for 60 min initiated a mechano-chemical reaction, resulted in spinel formation at much lower temperatures than within non-activated powders, and indicated that final sintering stage started at much lower temperatures for activated powders. Changes in microstructure parameters, as a consequence of mechanical treatment and subsequent heating of investigated powder mixtures, strongly affect electrical and mechanical properties of the final ceramics.


Materials Science and Engineering


This investigation was supported by the Serbian Ministry of Education, Science and Technological Development of the Republic of Serbia , and it was conducted under the following projects: OI 172057 , III 45007 and III 45019.

Keywords and Phrases

Electrical properties; Mechanical activation; Mechanical properties; Microstructure; Sintering; Spinel

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Article - Journal

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© 2019 Elsevier Ltd and Techna Group S.r.l. , All rights reserved.

Publication Date

01 Jun 2019