High-temperature heat capacity and thermal expansion of the MnTa2O6

The sample of the MnTa2O6 manganese tantalate was synthesized from MnO and Ta2O5 mixture by the ceramic technique. According to XRD it was a single-phase sample with an orthorhombic structure (sp.gr. Pbcn) and unit cell parameters: a = 14.4478(2) angstrom; b = 5.7677(1) angstrom; c = 5.0943(1) angstrom; V = 424.52(1) angstrom(3) . Heat capacity was measured by differential scanning calorimetry in the range of 323-1203 K in a dynamic mode. Experimental molar heat capacity was fitted to C-p.m = 191.33 + 67.451 x 10(-3) T 32.71 x 10(5) T-2 - 18.76 x 10(-6) T-2 equation based on which the value of the C-p.m29(8.15)(MnTa2O6) = 173.0 +/- 1.7 J mol(-1)K(-1) was calculated. By HT-XRD thermal dependences of the MnTa2O6 unit cell parameters in the temperature range of 300-1203 K were established. From the data obtained thermal expansion coefficients and anisotropy factors were calculated. Thermal expansion anisotropy was linked to the layered structure of the oxide. The correlation among molar heat capacity values and volume thermal expansion coefficients were revealed. (C) 2020 Elsevier B.V. All rights reserved.