Influence of Heavy Metal Oxides (HMOs: PbO and Bi2O3) on structural and photoluminescence (PL) properties Eu3+ activated lanthanum borate glasses has been analyzed and discussed in thoroughly here. When the PbO is loaded more and more in the glass system, the luminesce intensity and lifetime values of D-5(0) -> F-7(2) transition of Eu3+ were improved for the excitation at 464 nm due to enhanced covalency of Eu-O bonds arose from the dual function of lead oxide in the structure of PbO varied glasses. The betterment in luminescence features are also attributed to the decrease of effective network phonon energy occurred because of the incorporation of lead oxide in the glass composition. On the other hand, the luminesce (emission intensity and lifetime values of 614 nm emission of Eu3+ under 464 nm excitation) results are completely upending as the Bi2O3 content increased gradually in the glass matrix. This reduction in luminescence properties are ascribed to the decrease of covalency of Eu-O and thus crystal field in the vicinity of Eu3+ site. The reduction of covalent character of Eu-O is due to two facts, one being the newly generated NBOs owing to the generation of BiO6 units with the incorporation of Bi2O3 in the glass matrix and the second, the development of Bi-O-Bi and Bi-O-B linkages. The luminescence and spectroscopic attributes evidently reveal the lead varied borate glass hosts are more beneficial than Bi2O3 varied borate glass hosts for optoelectronic applications
