Highly Transparent LiAl ₅ O ₈ Ceramics Prepared by Spark Plasma Sintering and Its Luminescence

ABSTRACT Transparent ceramics of LiAl 5 O 8 were prepared by spark plasma sintering (SPS) using precursor powders synthesized via solid‐state reaction. The effects of sintering dwell time and cooling regime on the microstructure, transparency, and cracking of the sintered ceramics were investigated. The dwell time at the sintering temperature influenced light scattering and consequently also the transparency of the ceramic samples. The two‐step cooling regime affected both the microstructure and transparency of the ceramics in addition to playing a critical role in preventing cracking of the samples. By optimizing the dwell time duration and cooling profile, crack‐free transparent ceramics with transmittance greater than 80% at 500 nm were achieved. The resulting LiAl 5 O 8 transparent ceramics exhibited luminescence originating mainly from Fe 3+ and Cr 3+ impurities. Furthermore, strong defect‐related emission was also observed under the high‐energy X‐ray excitation.