Formation of Sodium Zirconium Silicophosphate with the Structure of Na3Zr2Si2РO12 from a Zr-Deficient Precursor

Samples of NASICON glass ceramics have been prepared by pyrolysis of a mixture of organic solutions in rosin melt. The phase formation, morphology, and characteristics of prepared silicophosphates have been discussed. A glass ceramics formed from precursor with molar component ratio Na : Zr : Si : P = 3 : 1.33 : 2 : 1 has been used for the study. Effect of additional phosphorus amount on the phase composition of sample has been investigated. It has been found that precursor of 3 : 1.33 : 2 : 1.15 composition produces densely sintered glass ceramics containing crystalline phase of Na₃Zr₂Si₂PO₁₂ composition. Product composition has been confirmed by unit cell parameters calculated by the Rietveld method. The samples have been obtained at 1000 and 1100°C without pressing and show 85 and 88% density of theoretical value, respectively. Conclusion has been drawn that not involved in crystal lattice Na, Si, and P take part in the formation of X-ray amorphous phase and provide conditions for NASICON formation by the type of liquid-phase sintering. A comparison of properties of Na₃Zr₂Si₂PO₁₂ ceramics obtained from Zr-deficient and non-deficient precursors has been made. It has been shown that glass phase formed in the intergrain space of Zr-deficient samples deteriorates the values of material conductivity.