Structure and polymorphism of complex phosphates prepared from fluxes of the Na2O-P2O5-Fe2O3-Nb2O5 system |
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| Authors: | I V Zatovsky T I Ushchapivska N S Slobodyanik I V Ogorodnyk |
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| Institution: | (1) Taras Shevchenko National University, Kiev, Ukraine;(2) National Agrarian University of Ukraine, Goloseevo, Kiev, 252041, Ukraine |
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| Abstract: | The phase formation of complex phosphates in the Na2O-P2O5-Fe2O3-Nb2O5 flux system was studied in the ranges of sodium-to-phosphorus ratios of 0.7–1.2 and iron-to-niobium ratios of 0.9–2.7. The crystallization region and crystallization conditions for the compounds of composition Na3?2x Fe2-x Nbx(PO4)3 (0.8 ≤ x < 1.2) were found. These compounds can be prepared in two (hexagonal and monoclinic) polymorphs. Single-crystal X-ray diffraction experiments were carried out for hexagonal NaFeNb(PO4)3 (space group $R\bar 3$ c, a = 8.590 Å, c = 22.013 Å). The polymorphism in Na3-2x Fe2-x Nbx(PO4)3 complex phosphates is considered as dependent on the preparation parameters. |
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