The Production of Transparent <scp> MgAl ₂ O ₄ </scp> Ceramic Using Calcined Powder Mixtures of <scp>Mg</scp> ( <scp>OH</scp> ) ₂ and γ‐ <scp> Al ₂ O ₃ </scp> or <scp>AlOOH</scp>

Abstract

Magnesium hydroxide, Mg ( OH ) 2 (both 99% and 99.99% purity grades), γ‐ Al 2 O 3 , and AlOOH have been investigated for the direct production of transparent MgAl 2 O 4 . The highest average in‐line transmittance through 3.5–4 mm thick samples is 84.2 ± 1.0% at 550 nm, attained by using mixtures of 99.99% pure Mg ( OH ) 2 and γ‐ Al 2 O 3 . Other formulations exhibited 77–80% visible transmission, suggesting that further optimization can improve sample consistency. All samples exhibited a Knoop hardness of ~12 GPa, and elastic modulus of ~280 GPa. Biaxial flexural strength measurements ranged from 85 to 136 MPa depending on starting materials.