Na3MnCO3PO4 (NMCP) is produced by hydrothermal synthesis for rechargeable sodium-ion battery (SIB) cathode. Mechanism of formation of NMCP was investigated by measuring the influence of time and temperature on the rate of production of the NMCP crystallites. X-ray diffraction analysis of the synthesized samples showed that MnCO3 first formed as an intermediate phase. Na3MnCO3PO4 was, however, the last phase retained after 24 h of the hydrothermal process at 120 degrees C. Sigmoidal shape of the crystallization curves followed the Avrami-Erofeev model which described the chemical kinetics of the Na3MnCO3PO4 formation. Respective apparent activation energies of 29.10 for nucleation and 73.91 kJ/mol for growth were obtained by application of the Arrhenius law to the experimental data and model calculations. ICP results showed that the Na to Mn ratio in the NMCP got closer to the stoichiometric value by increasing temperature and time of the hydrothermal reaction. Application of the NMCP as a cathode material for sodium ion batteries revealed that the specific capacity was improved by enhancing the degree of crystallinity. (C) 2018 Elsevier B.V. All rights reserved.