Physical Studies On Vitreous Na_2O-TiO_2-P_2O_5 System : Condensed Matter: Structure, etc.

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Three glasses of Na_2O-TiO_2-P_2O_5 system were prepared by melting the appropriate amounts of Na_2CO_3, TiO_2 and (NH_4)_2HPO_4 in an open crucible. The DTA thermal analysis showed crystallization temperature decreases with increasing sodium content in the sample. The structures of the virgin and annealed glasses (at 900 K for 4h) were studied using FT-IR, X-ray diffraction (XRD) and scanning electron microscope (SEM). Different crystalline phases depending on the compositions of the glasses were formed after annealing. The framework of the glasses was found to be made of PO_4, TiO_4 tetrahedral groups as well as TiO_6 entities that coexist with sodium modifier ions. TiO_2 enters the structure in tetrahedral or octahedral coordination in all samples. The temperature dependence of electrical conductivity, dielectric constant and dielectric loss for the virgin and annealed glasses is studied over a temperature range between 300 and 600 K and at a frequency from dc to 10^6 Hz. Many breaks, depending on both the composition and heat treatment of the samples, are observed on the plots of ln vs. 1/T. The conductivity increased by annealing and the results were explained on the basis of hopping Na^+ ions in the glass matrix. The ac-onductivity increased with frequency according to _<ac> () = A_<^s), where s has a value in the range 0.4-0.8 depending on the temperature and the composition of the sample. The temperature dependence of the dielectric constant showed that at relatively lower temperatures the electric dipoles formed in the glasses are frozen and starting to rotate at higher temperatures. Each of ' and was found to be dependent on the composition and the crystalline phases formed in the matrix. All the results have been discussed and correlated together.
社団法人日本物理学会の論文
2000-05-15

Physical Studies On Vitreous Na_2O-TiO_2-P_2O_5 System : Condensed Matter: Structure, etc.

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