Thermodynamic properties of sodium pentatitanate (Na₈Ti₅O₁₄)

Abstract

High-purity Na₈Ti₅O₁₄ was synthesized using Na₂CO₃ and TiO₂ as the starting materials by a solid-phase reaction. Heat capacity of Na₈Ti₅O₁₄ was measured by PPMS at low temperatures and MHTC 96 line at high temperatures. The changes in enthalpy at 298.15 K were $\Delta_{0}^{{298.15\;{\text{K}}}} H_{{\rm m}}$ = 95.43 kJ mol⁻¹, and standard molar entropy was $S_{{\rm m}}^{\theta }$ = 569.35 J\,mol⁻¹\,K⁻¹, respectively. The changes in enthalpy ($\Delta_{298.15}^{{T_{{\rm m}} }} H_{{\rm m}}$), entropy ($\Delta_{298.15}^{{T_{{\rm m}} }} S_{{\rm m}}$), and Gibbs energy ($\Delta_{298.15}^{{T_{{\rm m}} }} G_{{\rm m}}$) from (298.15 to 1303) K were calculated using heat capacity functions.