Thermal Relaxation Calorimetry Research Articles

Low-Temperature Heat Capacity of CsPbI3, Cs4PbI6, and Cs3Bi2I9.

The heat capacities of CsPbI3, Cs4PbI6, and Cs3Bi2I9 were studied using low-temperature thermal relaxation calorimetry in the temperature range of 1.9-300 K. The three compounds are insulators, with no electronic contribution to the heat capacity. None of them show detectable anomalies in the studied temperature window. Thermodynamic properties at standard conditions are derived. Previously reported results on Cs3Bi2I9 are not fully consistent with the present findings. Moreover, the magnetic susceptibilities of the three title compounds were measured.

Zn-Mo-O system: Insights into the thermodynamic stability and applicability in lithium ion batteries

A detailed experimental investigation on the thermochemical stability of Zn2Mo3O8(s) in the Zn-Mo-O system was reported for the first time using high temperature oxide melt solution calorimetry in conjunction with solid oxide based electrochemical measurements. The temperature dependence of molar heat capacity of this compound was determined employing thermal relaxation calorimetry and differential scanning calorimetry. The values of standard molar enthalpy of formation (∆fH298.15°), standard molar entropy (S298.15°), molar heat capacity (Cp) and Debye temperature (θD) for Zn2Mo3O8(s) were determined for the first time in this study. The present study also focuses on the investigation of electrochemical performance of α-ZnMoO4(s) for lithium ion battery applications which demonstrated the effective utilization of this compound as anode material due to its remarkable cycling stability and rate capability.

A comprehensive investigation on CdO-SnO2 system: Structure, thermal expansion and energetics

An extensive investigation into the thermochemical stability of two ternary oxides, ilmenite-type CdSnO3(s) and orthorhombic Cd2SnO4(s), in the Cd-Sn-O system was reported for the first time using high temperature oxide melt solution calorimetry in conjunction with differential scanning calorimetry and thermal relaxation calorimetry. The values of standard molar enthalpy of formation (∆fH298.15°), standard molar entropy (S298.15°), molar heat capacity and Debye temperature (θD) for ilmenite-type CdSnO3(s) and orthorhombic Cd2SnO4(s) were determined. Using the experimentally obtained thermochemical data, the standard molar Gibbs energy of formation of these compounds were derived and the corresponding expressions are given as follows:∆fGm°<CdSnO3>±1.3kJmol−1=−847.9+0.2781(T/K)(T:298.15−1000K)∆fGm°<Cd2SnO4>±3.6kJmol−1=−1138.1+0.3831(T/K)(T:298.15−1000K)Moreover, high temperature XRD experiments were conducted to evaluate their thermal expansion behaviour as well as for the in-situ identification of phase evolution resulting from decomposition of cadmium stannates.

Experimental and Computational Exploration of the NaF-ThF4 Fuel System: Structure and Thermochemistry.

The structural, thermochemical, and thermophysical properties of the NaF–ThF4 fuel system were studied with experimental methods and molecular dynamics (MD) simulations. Equilibrium MD (EMD) simulations using the polarizable ion model were performed to calculate the density, molar volume, thermal expansion, mixing enthalpy, heat capacity, and distribution of [ThFn]m− complexes in the (Na,Th)Fx melt over the full concentration range at various temperatures. The phase equilibria in the 10–50 mol % ThF4 and 85–95 mol % ThF4 regions of the NaF–ThF4 phase diagram were measured using differential scanning calorimetry, as were the mixing enthalpies at 1266 K of (NaF/ThF4) = (0.8:0.2), (0.7:0.3) mixtures. Furthermore, the β-Na2ThF6 and NaTh2F9 compounds were synthesized and subsequently analyzed with the use of X-ray diffraction. The heat capacities of both compounds were measured in the temperature ranges (2–271 K) and (2–294 K), respectively, by thermal relaxation calorimetry. Finally, a CALPHAD model coupling the structural and thermodynamic data was developed using both EMD and experimental data as input and a quasichemical formalism in the quadruplet approximation. Here, 7- and 8-coordinated Th4+ cations were introduced on the cationic sublattice alongside a 13-coordinated dimeric species to reproduce the chemical speciation, as calculated by EMD simulations and to provide a physical description of the melt.

Ultrasensitive Calorimetric Measurements of the Electronic Heat Capacity of Graphene.

Heat capacity is an invaluable quantity in condensed matter physics and yet has been completely inaccessible in two-dimensional (2D) van der Waals (vdW) materials, owing to their ultrafast thermal relaxation times and the lack of suitable nanoscale thermometers. Here, we demonstrate a novel thermal relaxation calorimetry scheme that allows the first measurements of the electronic heat capacity of graphene. It is enabled by combining a radio frequency Johnson noise thermometer, which can measure the electronic temperature with a sensitivity of ∼20 mK/Hz1/2, and a photomixed optical heater that modulates Te with a frequency of up to Ω = 0.2 THz. This allows record sensitive measurements of the electronic heat capacity Ce < 10 -19 J/K and the fastest measurement of electronic thermal relaxation time τe < 10 -12 s yet achieved by a calorimeter. These features advance heat capacity metrology into the realm of nanoscale and low-dimensional systems and provide an avenue for the investigation of their thermodynamic quantities.

Experimental studies and thermodynamic assessment of the Ba-Mo-O system by the CALPHAD method

Thermodynamic measurements on BaMoO4, BaMoO3 and BaMo3O10 are reported, that served as input for the development of a thermodynamic model of the Ba-Mo-O system using the CALPHAD methodology. The valence states of molybdenum in BaMoO4 and BaMoO3 were confirmed to be VI and IV, respectively, from X-ray Absorption Near Edge Structure Spectroscopy measurements at the Mo K-edge. The heat capacity at low temperatures of these compounds was obtained from thermal-relaxation calorimetry. Phase equilibrium data in the BaMoO4-MoO3 section were also measured, and the transition enthalpy associated with the peritectic decomposition of BaMo3O10 was determined using Differential Scanning Calorimetry. The developed thermodynamic model used the compound energy formalism for intermediate compounds, and an ionic two-sublattice model for the liquid phase. The optimized Gibbs energies were assessed with respect to the known thermodynamic and phase equilibrium data. A good agreement is generally obtained, but a number of ill-defined data were also identified.

Report of the Double-Molybdate Phase Cs2Ba(MoO4)2 with a Palmierite Structure and Its Thermodynamic Characterization.

The existence of a novel double-molybdate phase with a palmierite-type structure, Cs2Ba(MoO4)2, is revealed in this work, and its structural properties at room temperature have been characterized in detail using X-ray and neutron diffraction measurements. In addition, its thermal stability and thermal expansion are investigated in the temperature range 298–673 K using high-temperature X-ray diffraction, leading to the volumetric thermal expansion coefficient αV ≈ 43.0 × 10–6 K–1. The compound’s standard enthalpy of formation at 298.15 K has been obtained using solution calorimetry, which yielded ΔfHm°(Cs2Ba(MoO4)2, cr, 298.15 K) = −3066.6 ± 3.1 kJ· mol–1, and its standard entropy at 298.15 K has been derived from low-temperature (2.1–294.3 K) thermal-relaxation calorimetry as Sm°(Cs2Ba(MoO4)2, cr, 298.15 K) = 381.2 ± 11.8 J K–1 mol–1.

Synthesis and characterization of Pt(Cu0.67Sn0.33)

Pt(Cu0.67Sn0.33) has recently been found in a natural sample. In order to be able to characterize this new ternary compound, we synthesized it from the elements. Samples were characterized by X-ray powder diffraction, differential scanning calorimetry, thermal relaxation calorimetry, and scanning electron microscopy studies. Density functional theory-based model calculations complemented the experimental studies. Pt(Cu0.67Sn0.33) was already formed at a relatively low temperature of 773 K. Rietveld refinement of Pt(Cu0.67Sn0.33) has been carried out in CuAu-type or L10-type structure, space group P4∕mmm, with Pt on 0,0,0 and disordered Cu and Sn on 12, 12, 12 and Z = 1. The lattice parameters are a = 2.823(1) Å, c = 3.64(1) Å, and V = 29.00(4) Å 3; which are in good agreement with values obtained earlier on the natural sample and with the results of DFT calculations. The vibrational entropy for Pt(Cu0.67Sn0.33) is S298.15vib = 79.9(7) J mol−1 K−1. The pressure dependence up to 36(2) GPa of the unit-cell volume and the lattice parameters and unit-cell volume have been obtained by synchrotron based powder diffraction using a diamond anvil cell. A fit of a 3rd-order Birch–Murnaghan equation of state to the Pt(Cu0.67Sn0.33) (p,V)-data results in a bulk modulus of B0 = 215(27) GPa and B′ = 5(2).

Thermodynamic assessment of the KF-ThF4, LiF-KF-ThF4 and NaF-KF-ThF4 systems

A thermodynamic assessment of the KF-ThF4 binary system using the CALPHAD method is presented, where the liquid solution is described by the modified quasichemical formalism in the quadruplet approximation. The optimization of the phase diagram is based on experimental data reported in the literature and newly measured X-ray diffraction and differential scanning calorimetry data, which have allowed to solve discrepancies between past assessments. The low temperature heat capacity of α-K2ThF6 has also been measured using thermal relaxation calorimetry; from these data the heat capacity and standard entropy values have been derived at 298.15 K: Cp,mo(K2ThF6,cr,298.15K)=(193.2±3.9) J·K-1·mol-1 and Smo(K2ThF6,cr,298.15K)=(256.9±4.8) J·K-1·mol-1. Taking existing assessments of the relevant binaries, the new optimization is extrapolated to the ternary systems LiF-KF-ThF4 and NaF-KF-ThF4 using an asymmetric Kohler/Toop formalism. The standard enthalpy of formation and standard entropy of KNaThF6 are re-calculated from published e.m.f data, and included in the assessment of the ternary system. A calculated projection of the NaF-KF-ThF4 system at 300 K and the optimized liquidus projections of both systems are compared to published phase equilibrium data at room temperature and along the LiF-LiThF5 and NaF-KThF5 pseudobinaries, with good agreement.

Thermodynamic study of Cs3Na(MoO4)2: Determination of the standard enthalpy of formation and standard entropy at 298.15 K

The enthalpy of formation at 298.15 K and low temperature heat capacity of Cs 3 Na(MoO 4 ) 2 have been measured for the first time in this work using solution calorimetry and thermal-relaxation calorimetry in the temperature range T = (1.9–299.6) K, respectively. The solution calorimetry measurements, performed in 2 M HNO 3 solution, have yielded an enthalpy equal to Δ r H m (298.15 K) = (6.79 ± 1.72) kJ · mol −1 for the reaction: 3 / 2 Cs 2 MoO 4 ( cr ) + 1 / 2 Na 2 MoO 4 ( cr ) = Cs 3 Na ( MoO 4 ) 2 ( cr ) Combining with the enthalpies of formation of Cs 2 MoO 4 (cr) and Na 2 MoO 4 (cr), also determined in this work in 0.1 M CsOH and 0.1 M NaOH solutions, respectively, the standard enthalpy of formation of Cs 3 Na(MoO 4 ) 2 at 298.15 K has been determined as Δ f H m o (Cs 3 Na(MoO 4 ) 2 , cr, 298.15 K) = −(2998.5 ± 3.0) kJ · mol −1 . The heat capacity and entropy values of Cs 3 Na(MoO 4 ) 2 at 298.15 K have been derived as C p , m o ( Cs 3 Na ( MoO 4 ) 2 , cr , 298.15 K ) = ( 296.3 ± 3.3 ) J · K −1 · mol −1 and S m o ( Cs 3 Na ( MoO 4 ) 2 , cr , 298.15 K ) = ( 467.2 ± 6.8 ) J · K −1 · mol −1 . Combining the newly determined thermodynamic functions, the Gibbs energy of formation of Cs 3 Na(MoO 4 ) 2 at 298.15 K has been derived as Δ f G m o ( Cs 3 Na ( MoO 4 ) 2 , cr , 298.15 K ) = - ( 2784.6 ± 3.4 ) kJ · mol −1 . Finally, the enthalpies, entropies and Gibbs energies of formation of Cs 3 Na(MoO 4 ) 2 from its constituting binary and ternary oxides have been calculated.

Effects of lanthanum content on the thermo-optical properties of (Pb,La)(Zr,Ti)O3

ABSTRACTIn this work the thermal lens spectrometry, the optical interferometry and the thermal relaxation calorimetry were employed to determine the thermo-optical properties of transparent ferroelectric ceramic (Pb,La)(Zr,Ti)O3 or PLZT, as a function of lanthanum concentration. The use of three independent techniques allowed the characterization of several thermo-optical parameters of the studied PLZT system. Parameters such as thermal diffusivity, thermal conductivity, optical path length change and temperature coefficient of the refractive index were determined. In addition, the results showed that the thermo-optical properties were significantly modified with the lanthanum concentration, these informations are important for the use of the PLZT system as host of active ions for laser generation.

Thermodynamic investigation by heat capacity measurements of ferrimagnetic A2Mn[Mn(CN)6] (A=K, Rb, Cs) Prussian blue compounds

Heat capacity measurements of a new series of Prussian blue analogs of A2Mn[Mn(CN)6] (A=K, Rb, Cs) composition were performed using thermal relaxation calorimetry. The Cs compound has a face-centered cubic structure with a linear Mn–C≡N–Mn linkage, while the monoclinic Rb and K compounds have nonlinear Mn–C≡N–Mn linkages. For all of the compounds, large broad thermal anomalies associated with magnetic transitions were observed in the temperature dependence of the heat capacity. The systematic changes in the heat capacity for the three compounds under magnetic fields of up to 7 T were found to be consistent with ferrimagnetic ordering with large spontaneous magnetization. Although the peak temperatures were slightly lower than reported values obtained by magnetic susceptibility measurements, the magnetic entropy was evaluated to be 22.0 ± 2.5 J K−1 mol−1. This value is consistent with an entropy of Rln12 corresponding to full entropy of one low-spin and one high-spin MnII ion in the formula unit, though some ambiguity remains in lattice estimation. Broadening of the peak width of the magnetic heat capacity divided by the temperature was observed as the size of the alkali ions decreased from Cs to K. This behavior is consistent with an increase in the lattice distortion produced by the bending of the C≡N–Mn angles.

Temperature dependence of the thermophysical properties of Neodymium doped borate glasses

We have experimentally measured the temperature dependence of the thermophysical properties of Nd 2O 3 doped borate glasses using a combination of the time resolved thermal lens technique with optical interferometry, thermal relaxation calorimetry and photoluminescence methods. Thermal diffusivity, thermal conductivity, fluorescence quantum efficiency, linear thermal expansion coefficient and thermal coefficient of the electronic polarizability were determined. The results showed the ability of these techniques to perform measurements very close to the glass transition region providing the absolute values of the measured physical quantities and the glass transition temperatures. In conclusion, it was observed that thermal lens and optical interferometry are advantageous methods for measurements as a function of temperature especially when low temperature scanning rate is required.

Heat capacities of antiferromagnetic dimer-Mott insulators in organic charge-transfer complexes

Heat capacity measurements of quasi-two-dimensional Mott insulating compounds consisting of BEDT-TTF (bisethylendithiotetrathiafulubalene) donor molecules and counter anions were performed by the thermal relaxation calorimetry technique for single crystal samples. No distinct thermal anomalies at the predicted antiferromagnetic transition temperatures in κ-(BEDT-TTF)2Cu[N(CN)2]Cl (T N = 27 K) and β′-(BEDT-TTF)2ICl2 (T N = 22 K) were observed. These results demonstrate that the Mott insulating state of the organic salts which are dominated by the strong two-dimensional intra-layer antiferromagnetic interactions between neighboring S = 1/2 spins shows somewhat different features from the simple quasi-two-dimensional Heisenberg model with S = 1/2. The strong quantum fluctuations produced by the electron correlations suppress the long-range character of the spin correlations, which seems to be an important aspect of this kind of Mott insulating materials.

Influence of temperature and excitation procedure on the athermal behavior of Nd3+-doped phosphate glass: Thermal lens, interferometric, and calorimetric measurements

In this work, thermal and optical properties of the commercial Q-98 neodymium-doped phosphate glass have been measured at low temperature, from 50 to 300 K. The time-resolved thermal lens spectrometry together with the optical interferometry and the thermal relaxation calorimetry methods were used to investigate the glass athermal characteristics described by the temperature coefficient of the optical path length change, ds/dT. The thermal diffusivity was also determined, and the temperature coefficients of electronic polarizability, linear thermal expansion, and refractive index were calculated and used to explain ds/dT behavior. ds/dT measured via thermal lens method was found to be zero at 225 K. The results provided a complete characterization of the thermo-optical properties of the Q-98 glass, which may be useful for those using this material for diode-pumped solid-state lasers.

Thermal lens and interferometric method for glass transition and thermo physical properties measurements in Nd_2O_3 doped sodium zincborate glass

In this work the time resolved thermal lens method is combined with interferometric technique, the thermal relaxation calorimetry, photoluminescence and lifetime measurements to determine the thermo physical properties of Nd(2)O(3) doped sodium zincborate glass as a function of temperature up to the glass transition region. Thermal diffusivity, thermal conductivity, fluorescence quantum efficiency, linear thermal expansion coefficient and thermal coefficient of electronic polarizability were determined. In conclusion, the results showed the ability of thermal lens and interferometric methods to perform measurements very close to the phase transition region. These techniques provide absolute values for the measured physical quantities and are advantageous when low scan rates are required.

Magnetic-Field-Induced Freezing of Spin Correlations in Networked System of [Mn4] Single-Molecule Magnets

A low-temperature thermodynamic measurement of a single crystal of [Mn 4 (hmp) 4 (pdm) 2 {N(CN) 2 } 2 ](ClO 4 ) 2 ·1.75H 2 O·2MeCN, which has a two-dimensional coordinating network consisting of Mn 4 single-molecule magnets (SMMs), was performed by thermal relaxation calorimetry. Magnetic ordering was observed at an extremely low-temperature of 380 mK at a zero field. We have found that the temperature dependence of heat capacity is strongly affected by applying weak magnetic fields owing to the large Zeeman effect occurring in the constituting SMM unit. When magnetic fields of 0.1–0.3 T are applied, an abrupt decrease in heat capacity is observed at approximately 0.9 K, which phenomenologically resembles the glass formation of molecular or macromolecular systems. The delicate balance between the Zeeman effect in each unit and the cooperative character of a network produces such a nonequilibrium magnetic state in this material.

Heat capacities of a networked system of single-molecule magnet with three-dimensional structure

A magnetic-fields dependence of heat capacity of [Mn5(hmp)4(OH)2{N(CN)2}6]2MeCN·2THF (hmp=hydroxymethylpyridinate) is investigated by the thermal relaxation calorimetry technique. This compound is a three-dimensional system consisting of Mn4 single-molecule magnet (SMM) units and Mn2+ ions, which are linked by the dicyanamide ligands to form a coordination network structure. A sharp peak of C p being associated with the formation of three-dimensional long-range order is observed around 1.96 K. The thermodynamic discussion based on the magnetic entropy suggests that both SMMs and Mn2+ ions are involved in the formation of the anitiferromagnetic spin ordering. However, this long-range ordering is very sensitive to the external magnetic fields which work to change the magnitude of the Zeeman splitting of the SMM levels. The behavior under magnetic fields is similar to that of the two-dimensional Mn4-network system studied previously.

Time resolved thermal lens measurements of the thermo-optical properties of Nd2O3-doped low silica calcium aluminosilicate glasses down to 4.3 K

In this work, the thermal lens spectrometry was applied to measure the thermo-optical properties of Nd2O3-doped low silica calcium aluminosilicate glasses as a function of temperature, between 4.3 and 300K. The thermal relaxation calorimetry was used to determine the specific heat, cp. The results showed a decrease of the thermal diffusivity of about one order of magnitude from 4.3K up to 300K, with a T−1 dependence in the interval between 20 and 70K and a T−0.35 between 4.3 and 20K. The fluorescence quantum efficiencies of the doped samples were calculated down to 50K, showing a variation of the order of 12% and 25% for the samples with 0.6 and 1.04mol% of Nd2O3, respectively. In addition, the temperature corresponding to the maximum in cp/T3, the so-called boson peak, was observed at about 17K for the undoped sample and at lower temperatures for the doped glasses. In conclusion, our results showed the ability of the time resolved thermal lens to determine the thermo-optical properties of glasses at temperatures lower than 300K, bringing new possibilities for experiments in a wide range of optical materials.

Contribution of low-frequency modes to the specific heat of Cu-Zn-Al shape-memory alloys

We report a comparison of the specific-heat measurements on isoelectronic Cu-Zn-Al shape-memory alloys in the parent cubic phase $(L{2}_{1})$ and in the close-packed martensitic phase $(18R)$. Measurements were made by thermal-relaxation calorimetry over the temperature range $1.9\ensuremath{\leqslant}T\ensuremath{\leqslant}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. For the close-packed martensitic phase we find that the specific heat behaves similarly to that of pure copper which is also close packed. However, we observe deviations from Debye behavior for the cubic phase at low temperatures. This deviation is accounted for by the addition of $\ensuremath{\sim}5%$ of Einstein localized modes to the Debye modes. Although the microscopic origin remains unknown, it was anticipated that it is related to the well-known softening of the ${\mathrm{TA}}_{2}[110]$ phonon branch. In order to address this hypothesis an analysis of the lattice heat capacity of the cubic phase was compared to the calculated lattice heat capacity of $\ensuremath{\beta}$-brass, as determined by integrating over the phonon density of states. A similar comparison was made between the close-packed phase and $\ensuremath{\alpha}$-brass.