1. Introduction
Amorphous [1] and crystalline [2] lead borates belong to the attractive solid-state materials from the structural and optical points of view. Especially, lead borate glasses were extensively studied in the recent years. Wide glass-forming region and quite easy preparation, high chemical stability and UV–vis-NIR light transmittance, presence of structurally different borate units are the most important and advantageous points of PbO–B2O3 systems, in the case of glass technology and structural investigations. Also, lead borate glass is promising host for incorporation of transition metal [3] and [4] and rare earth [5] and [6] ions. The results earlier obtained for Nd3+[5] and Eu3+[6] ions indicate that their luminescent properties strongly depend on PbO/B2O3 ratio in glass composition.