Low-temperature heat capacity and thermodynamic functions of thulium and lutetium titanates and Schottky anomaly in Tm2Ti2O7. (February 2022)

• Record Type: Journal Article
• Authors: Bissengaliyeva, Mira R.; Knyazev, Alexander V.; Bespyatov, Michael A.; Gogol, Daniil B.; Taimassova, Shynar T.; Zhakupov, Ramazan M.; Sadyrbekov, Daniyar T.
• Is Part Of: Journal of chemical thermodynamics. Volume 165(2022)
• Publication Date: 2022-02
• Subjects: Rare earth titanates -- Adiabatic calorimetry -- X-ray diffraction -- Heat capacity -- Schottky anomaly -- Thermodynamic properties; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2021.106646
• Languages: English
• ISSNs: 0021-9614

Abstract

Highlights: Thulium and lutetium titanates were synthesized from oxides by solid state reaction. Structural refinement and measurements by adiabatic calorimetry were carried out. Anomal Schottky contribution in Tm2 Ti2 O7 and thermodynamic functions were determined. Abstract: The temperature dependence of the heat capacity of Tm2 Ti2 O7 and Lu2 Ti2 O7 compounds over the range of 4.5–320 K has been researched by adiabatic calorimetry. Based on the experimental data, the basic thermodynamic functions of the compounds over the range of 5–320 K have been determined. Tm2 Ti2 O7 sample has revealed an additional component in the heat capacity associated with the presence of the Schottky anomaly. The temperature dependence behavior of the Debye characteristic temperature of Lu2 Ti2 O7 sample indicates the absence of anomalies in the heat capacity. Standard thermodynamic functions at 298.15 K are: for Tm2 Ti2 O7 – Cp, 298.15 = 221.0 ± 1.2 J·mol − 1 ·K − 1, S 298.15 = 261.3 ± 2.4 J·mol − 1 ·K − 1, Δ H 0 298.15 = 39.45 ± 0.29 kJ·mol − 1 ; for Lu2 Ti2 O7 – Cp, 298.15 = 206.9 ± 1.1 J·mol − 1 ·K − 1, S 298.15 = 229.8 ± 2.2 J·mol − 1 ·K − 1, Δ H 0 298.15 = 35.70 ± 0.26 kJ·mol − 1 .