Synthesis of NaTi₂(PO₄)₃ by the Inorganic–Organic Steric Entrapment Method and Its Thermal Expansion Behavior

Crystalline pure NaTi₂(PO₄)₃ (NTP) powder was synthesized at 700°C using a simple and low energy, hybrid inorganic–organic, steric entrapment method. Sodium nitrite (NaNO₂) and ammonium phosphate dibasic ((NH₄)₂HPO₄) dissolved in water, whereas titanium (IV) isopropoxide (Ti[OCH(CH₃)₂]₄) hydrolyzed in water. Ethylene glycol (HOCH₂CH₂OH) was used as a polymeric entrapper and hydrolysis of the Ti source was hindered by its dissolution in isopropyl alcohol. The resulting NTP powder was characterized by thermogravimetric analysis/differential thermal analysis, X-ray diffractometry, scanning electron microscopy, specific surface area by Brunauer–Emmett–Teller nitrogen absorption, and particle size analysis. Furthermore, C, H, N were measured by the classical Pregl-Dumas method. The thermal expansion behavior in all {hkl} pole directions was also determined by in situ high-temperature X-ray diffraction using synchrotron radiation and was found to be in agreement with other published studies.