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Self-diffusion Coefficients of Na⁺ Ion in NaPO₃-Al(PO₃)₃ Glasses about Transition Temperatures

1964; Ceramic Society of Japan; Volume: 72; Issue: 817 Linguagem: Inglês

10.2109/jcersj1950.72.119

1884-2127

Ryôhei TERAI,

Microwave Dielectric Ceramics Synthesis

Self-diffusion coefficients of Na+ ion in NaPO3-Al(PO3)3 glasses at temperatures about transition points were measured by means of tracer technique using radio-isotope 22Na.The counting of radio-activity at successively ground surfaces gave better results than that of powders removed by grinding because of less experimental errors.The activation energies for the diffusion of Na+ ion above and below transition points were 30kcal/mole and 20kcal/mole respectively, which were in accord with the values in silicate glasses and were also agreed with the activation energies for the electrical conductivity of these glasses.According to a corrected Nernst-Einstein equation, the relation between diffusion coefficient, Di, and the electrical conductivity, σ, of solid is given byDi=σtikT/niZi2e2⋅fwhere ti is the transfer number, k is Boltzmann constant, T is the absolute temperature, ni is the number of ions per cubic centimeter, Zi is the valence, e is the electronic charge, f is the correlation factor named by Bardeen and Herring.The f-value obtained from the author's experiment was about 0.15-0.25, and this value was maintained at temperatures above and below the transition point. It was interpreted, therefore, that the transport mechanism of Na+ ion in these glasses about transition temperatures is one of the indirect interstitial (interstitialcy) transport rather than the simple vacancy transport.