Al2O3 doped with transition metal Cr3+ doped with transition metal Cr3+ ion is the most important phase for laser hosts, possessing excellent emitting properties [17–20]. Aluminum oxide (Al2O3 ) plays a key role in many technologies due to its remarkable physical properties, such as a high melting point, hydrophobicity, high elastic modulus, high optical transparency, high refractive index of about 1.76 at 632.8 nm wavelength, thermal and chemical stability, low surface acidity, and fine optical and dielectric characteristics [21–24]. It can act as a tunnelling barrier for novel magnetic sensors and for organic transistors because of its large band gap (8 eV) [25].