Microstructure, mechanical, EPR and optical properties of lithium disilicate glasses and glass–ceramics doped with Mn2+ ions

• Published in: Journal of alloys and compounds 2012-01, Vol.512 (1), p.105-114
• Main Authors: Molla, A.R., Chakradhar, R.P.S., Kesavulu, C.R., Rao, J.L., Biswas, S.K.
• Format: Article
• Language: English
• Subjects: Alloys; Cross-disciplinary physics: materials science; rheology; EPR; Exact sciences and technology; Glass; Glasses (including metallic glasses); Glass–ceramics; Heat treatment; Iron; Lithium; Materials science; Mechanical properties; Microstructure; Modulus of rupture in bending; Optical; Optical properties; Physics; Specific materials
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2011.09.031

► Mechanical, EPR and optical properties of LDS glass–ceramics are studied. ► Nano-sized crystals are developed with elongated, interlocked microstructures. ► High fracture toughness of ∼2.8MPam1/2 have been obtained. ► Cerammed samples upon 394nm excitation emit a green luminescence at 565nm. ► EPR spectra show signals with g values at g=4.73, g=4.10, g=3.3 and g=1.98. The microstructure, mechanical, EPR and optical properties of transparent MnO2 doped lithium disilicate (LDS) glass–ceramics prepared by melt quenching and controlled crystallization, have been studied. The microstructure of the glass–ceramics has been characterized using FE-SEM, TEM, FT-IR and XRD techniques. FE-SEM micrographs show elongated, highly interlocked, dense (∼80vol.%) nanocrystals of LDS with an average size ∼100nm. XRD and FT-IR studies reveal that the only crystalline phase formed after heat-treatment at 700°C for 1h is LDS. A good combination of average microhardness ∼5.6GPa, high fracture toughness ∼2.8MPam1/2, 3-point flexural strength ∼250MPa and moderate elastic modulus 65GPa has been obtained. The EPR spectra of both LDS glasses and glass–ceramics exhibit resonance signals with effective g values at g=4.73, g=4.10, g=3.3, and g=1.98. The resonance signal at g=1.98 is found to be more intense than the other signals and exhibits hyperfine structure at lower concentration of manganese. From the observed spectrum, the spin-Hamiltonian parameters have been evaluated. In glass samples the optical absorption spectrum exhibits a broad band around ∼20,320cm−1 which has been assigned to the transition 6A1g(S)→4A1g(G) 4Eg(G)-of Mn2+ ions. The cerammed samples upon 394nm excitation emit a green luminescence (565nm, 4T1g→6A1g(G) transition of Mn2+ ions), and a weak red emission (710nm). From the ultraviolet absorption edges, the optical bandgap energies (Eopt) were evaluated and are discussed.