Optical absorption and EPR studies of borate glasses with PbCrO4 and Pb2CrO5 microcrystals

• Published in: Journal of materials science Vol. 27; no. 2; pp. 511 - 519
• Main Authors: Ram, S., Ram, Kanik, Shukla, B. S.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 1992
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Infrared and raman spectra and scattering; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Heat treatment; Visible absorption; Glass; Infrared absorption; Electron paramagnetic resonance; Experimental study; Inorganic compound
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00543945

The optical absorption (in the 400-1000 nm region) and electron paramagnetic resonance (EPR) spectra of 50PbO- 20Cr2O3-(30-y)B2O3-yAl2O3 glasses and those crystallised by suitable thermal treatments have been studied. The results are applied to account for the crystallisation process, which revealed the crystalline products due to PbCrO4 and Pb2CrO5, and crystallisation yield was found to be drastically enhanced (by as much as approx. 85 vol%) with Al2O3 additives. The addition of Al2O3 in the present glasses and/or the thermal treatments induce the optical absorption intensity in the visible region at the expense of the near infra-red region and reflect a gradual decrease in the EPR linewidth, delta H, at g approx. 2. The chromium in these cases most likely exists in a thermodynamic equilibrium between Cr3+ and Cr6+ oxidation states and the Al2O3 favours the reversible Cr3+ to Cr6+ nucleation transformation to accord with the above observations. In addition, the crystalline PbCrO4 and Pb2CrO5 comprise CrO4(2-) groups with the Cr6+ oxidation state of chromium. 27 refs.