Method for correcting experimental values of the heat capacity of REE compounds by the debye temperature

Title : Method for correcting experimental values of the heat capacity of REE compounds by the debye temperature

Abstract:

This paper considers a method for correcting deviations in the heat capacity of the compounds of rare earth elements (REE) having an anomalous contribution to the heat capacity and for which there is an isostructural compound without additional contributions. For example, erbium and thulium titanates are such compounds, the heat capacity of which was measured by adiabatic calorimetry [1,2]. The splitting of the main term of paramagnetic Ln³⁺ ions with an incomplete 4f-shell by the crystal field removes the degeneracy of the Stark levels, the thermal population of which by electrons leads to the appearance of a Schottky contribution to the heat capacity. An isostructural analogue for them is lutetium titanate Lu2Ti2O7, which is a diamagnetic compound.

Owing to the characteristics of the measurements, there is an increased scatter of experimental points from the smoothed curve over the temperature range from approximately 45 to 70 K. Nevertheless, it does not go beyond the 95% confidence interval. However, upon isolating an additional constituent of the heat capacity (Schottky contribution) composing a small value relatively to the total heat capacity, these deviations become noticeable and can affect the form of the anomalous component.

For a more accurate calculation of the lattice component of the heat capacity, a correction is used for the temperature dependence of the characteristic Debye temperature [3]:

θ_D(Lu)/θ_D(Ln) = [M_r(Ln)/M_r(Lu)]^1/2.

After subtracting the lattice heat capacity, upon availability of deviations in the anomalous component, for correction the smooth sections of the dependence are described by suitable equations, to which the deviated values are reduced within the typical scatter of the experimental points in the given temperature range.

Audience - Take Away:

• Obtaining novel data on the heat capacity, thermodynamic functions and magnetic properties of REE compounds.
• Methods for isolating heat capacity components and physicochemical interpretation of the results from the standpoint of crystal field theory.
• Identifying patterns in paramagnetic and ferromagnetic materials with cooperative and non-cooperative interactions.
• Widening scientific knowledge on the properties of rare earth elements promotes the development of a technological and energy sector of industry, including green energy, wind power engineering, and hydrogen energy.

Biography:

Dr. Bissengaliyeva studied Chemistry at the Karaganda State University and graduated as MS in 1977. She then joined the research group of Prof. Bekturganov at the Abishev Chemical-Metallurgical Institute, Kazakhstan Academy of Sciences. She received her PhD degree in 1990 at the same institution. Since 2004 she has been working at the Institute for Institute of Problems of Complex Development of Mineral Resources as Head of the Mineral Processing Laboratory. In 2010 she received the academic degree of Doctor of Sciences (Chemistry) and the academic title of Full Professor. She has published more than 80 research articles in scientific journals.