Use of the regular melting-quench method allowed the isolation of a small glass domain within the ternary system Li 2 O-P 2 O 5 -Cr 2 O 3 at 1000˚C. Electrical conductivity and dielectric permittivity measures on sample glasses and ceramic glasses of this domain were performed at a frequency of 10 kHz and at temperatures between 25˚C and 300˚C. The values of dielectric permittivity and electrical conductivity increase with increasing Li 2 O content. However, increases of Cr 2 O 3 content, even

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... t low concentrations, induce a change in electrical conductivity behaviour from that of a glass to that of a ceramic glass. The introduction of an increasing amount of Li 2 O content in vitreous phosphorus pentoxide changes its three-dimensional network; rupture of the P-O-P bond then occurs and there is formation of easily polarisable entities with quite high values of r ε ′ . The vibrational spectroscopy technique I.R has allowed an efficient investigation of the structural change versus composition within the above indicated ternary diagram. The maximal dielectric permittivity obtained at 300˚C, both for the glasses and for the ceramic glasses varied in the order 10 4 to 3 × 10 5 , while the maximum electrical conductivity obtained at 300˚C for the ceramic glasses was in the order of 10 −3 Ωcm −1 .