Synthesis, characterization and thermodynamic properties of KNbO3

The potassium niobate (KNbO3) sample was hydrothermally synthesized using Nb2O5 and KOH solution as precursors. X-ray diffraction (XRD) results show that the KNbO3 is a single-phase material with an orthorhombic crystal structure unit cell parameters are: = 3.9743 (2) Å; b 5.6954 c 5.7229 ? ? ? 90°, V 129.54 (1) Å3. temperature-dependent phase transitions enthalpy changes of were investigated by Differential Scanning Calorimetry (DSC) method. heat capacity measured experimentally relaxation time method via physical property measurement system (PPMS, 2–300 K) DSC sapphire (280–820 K), respectively. (2–300 piecewise fitted into polynomials as: Cp 3.242 × 10?1 T + 1.540 10?3 T3 1.056 10?4 T5-1.098 10?6 T7 2.946 10?9 T9 (2–10 3.275 0.005 0.044 T2-6.816 4.628 10?5 T4-1.343 T5 1.090 10?8 T6 (10–50 88.211 69.280 T-0.580 105 T?2-8.685 T2 (50–300 K). Consequently, enthalpy, entropy, Gibbs free energy equilibrium constant calculated based dependence temperature