Glass formation between PbO and KF is reported. The influence of composition on thermal stability, density, molar volume, refractive index, optical band gap, Urbach energy, and Pb2+emission spectra are presented. While KF influences thermal stability, the PbO content markedly influences the optical properties due to the formation of strong ‐Pb‐O‐Pb‐ covalent linkages. Increasing PbO content also results in phonon assisted nonradiative decay from1P1and3P1levels to3P0level leading to a marked decrease in the1P1→1S0emission. ©1995 American Institute of Physics.