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.