hrvatski

Utjecaj strukture na dielektrična svojstva LiZnPO4 stakala

Lithium zinc phosphate glasses of the molar composition xLi2O-(40-x)ZnO-60P2O5, (0 ≤ x ≤ 40 mol%), (LiZnP), were prepared by melting homogeneous mixtures of reagent grade Li2CO3, ZnO, NH4H2PO4, in dense alumino-silicate crucible at 1127 K in air for 2 hours. Glasses were analysed by differential thermal anaylsis (DTA), Raman and Impedance Spectroscopy in the frequency range from 0.01 Hz to 4 MHz and temperature range from 298 to 473 K. The systematic change in the variety of properties at 20 mol% Li2O is explained by changes in the nature of the oxygen bonds in glass network [1]. The Raman spectra predominantly show the metaphosphate structure with barely detectable pyrophosphate units for all glasses in the series. However, replacing ZnO with Li2O in these glasses leads to the compositional dependent changes. This dependence is explained by different structural cross-linking of phosphate chains with increasing Li2O, which is correlated with the unusual minimum in Tg and Δ Ts at 519 K and 317 K, respectively, for glass containing 20 mol% Li2O. The dielectric permittivity, ε `(ω ), and loss, ε " (ω ), measured at 298 K and 1 Hz, as a function of Li2O, shows a minimum at 20 mol% Li2O whereas at 473 K almost lineary increases with increasing Li2O content. This suggest that the dielectric permittivity is directly related to the thermally stimulated mobility of Li+ ions in the high temperature region. The dependence of dielectric strength of the ionic relaxation [2], determined as Δ ε = ε s – ε ∞ , exhibits the lowest value at 20 mol% Li2O. Dielectric strength, Δ ε , is the magnitude of the permittivity change due to ionic relaxation and it increases with further increase of Li2O content up to 40 mol%. The observed minimum in ε `(ω ) and ε " (ω ) correspondes well with the drop in Tg and Δ Ts. These changes in the dielectric properties at 20 mol% Li2O correspond to the discrete restructuring in glass network.

fosfatna stakla; električna svojstva; mikrostruktura

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