LOW-TEMPERATURE HEAT CAPACITY AND THERMODYNAMIC FUNCTIONS OF A Gd2(MoO4)3 SINGLE CRYSTAL
Bespyatov M.A., Cherniaikin I.S., Pavlyuk A.A., Gelfond N.V.
Nikolaev Institute of Inorganic Chemistry SB RAS
630090, Novosibirsk, Acad. Lavrentiev Ave., 3
Rare-earth molybdates, including Gd2(MoO4)3, are of considerable practical interest due to their nonlinear optical and ferroelectric properties, which underpin their applications in photonics and optoelectronic devices. Reliable thermodynamic data, in particular high-precision heat capacity over a wide temperature range, are essential for an adequate description of their physical behavior. Available literature data are limited to temperatures below 4.2 K and the 60–305 K interval and have been obtained for polycrystalline samples, thus precluding a consistent thermodynamic description of single-crystalline Gd2(MoO4)3 over an extended temperature range.
Gadolinium molybdate single crystal and titanium calorimeter container
In this work, a large optically homogeneous single crystal of gadolinium molybdate (Gd2(MoO4)3) was grown using the low-thermal-gradient Czochralski method and comprehensively characterized in terms of its phase, elemental, and impurity composition. For calorimetric measurements, a cylindrical sample was prepared from the crystal, precisely matching the dimensions of the inner cavity of the calorimeter container. High-precision heat capacity data in the temperature range 6–330 K were obtained by adiabatic calorimetry using a BKT-20 calorimeter [1]. Based on the experimental data, thermodynamic functions (entropy, enthalpy and reduced Gibbs energy) were calculated for the entire studied temperature range. Low-temperature heat capacity data below 4.2 K from the literature were consistently incorporated to ensure correct extrapolation to 0 K. The results obtained in our study were compared with literature data.
1. Bespyatov M.A. // J. Chem. Eng. Data 2025. V. 70. P. 3630.
The research was supported by the Ministry of Science and Higher Education of the Russian Federation.