Monoclinic M′-orthotantalate thulium samples were obtain by co-precipitation and annealing at 1873 K and characterized by X-ray powder diffraction, scanning electron microscopy and chemical analysis. ...Using the high-temperature X-ray diffraction method, the temperature dependences of the monoclinic lattice parameters were determined at range 298–1273 K and instantaneous βV(i) and relative βV(r) volume expansion coefficients were calculated. The molar heat capacity of M′-TmTaO4 was measured by relaxation (4.1–25.1 K), adiabatic (5.6–348.8 K) and differential scanning (303–1333 K) calorimetry. Standard thermodynamic function (entropy, enthalpy increment and reduced Gibbs energy) were calculated on the smoothed values of molar capacity, without taking into account the contribution of phase transformations occurring below 4 K. The general shape of the anomalous Schottky contribution to the molar heat capacity was determined.
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•M‘-TmTaO4 synthesis was carried out by coprecipitation and calcination at 1873 K.•Thermal expansion of M‘-TmTaO4 was measured by HTXRD at 298–1273 K.•Heat capacity of M‘-TmTaO4 was measured by relaxation, adiabatic and differential scanning calorimetry 4–1333 K.•Thermodynamic functions M‘-TmTaO4 were calculated.
The heat capacity of europium stannate with the pyrochlore structure was measured in the temperature range 3–1350 K using relaxation, adiabatic, and differential scanning calorimetry. The entropy, ...enthalpy change, and derived Gibbs energy of Eu
2
Sn
2
O
7
were calculated from the fitted heat capacity data. The temperature-dependent excess heat capacity related to Schottky’s anomaly was described in terms of the Westrum model. The Gibbs energies of formation Δ
f
G
°(Eu
2
Sn
2
O
7
) from elements and from constituent binary oxides were estimated from literature data and the values obtained in this work. An analysis of the magnetic properties of europium stannate showed the absence of magnetic phase transitions in the temperature range from 2 to 300 K. Thermal expansion coefficients were calculated from the unit cell parameters measured by high-temperature X-ray diffraction experiments in the range 300–1273 K.
Gadolinium hafnate samples were obtained by co-precipitation and precursor annealing at a temperature of ~1773 K and characterised by X-ray powder diffraction, scanning electron microscopy and ...chemical analysis. The molar heat capacity of Gd2Hf2O7 ceramics with a pyrochlore structure was measured by adiabatic (8–340 K) and differential scanning calorimetry (315–1345 K). The heat capacity of gadolinium hafnate was extrapolated to 0 K without taking into account anomalies in the temperature range below 20 K. Standard thermodynamic functions were calculated based on the smoothed values of molar heat capacity: entropy, enthalpy change and reduced Gibbs energy. Using the high-temperature X-ray diffraction method, the temperature dependence of the Gd2Hf2O7 cubic crystal lattice parameter was determined in the range of 298–1273 K and coefficients of instantaneous (αi), relative (αr) and linear thermal expansion (TE) were calculated.
Monoclinic dysprosium orthotantalate ceramics were synthesised by reverse co-precipitation followed by annealing at 1773 K and characterized by X-ray powder diffraction, scanning electron microscopy ...and chemical analysis. High-temperature X-ray diffraction was used to study change in the lattice parameters in the temperature range of 298–1273 K, and the volume expansion of M-DyTaO4 ceramics was calculated. The molar heat capacity of M-DyTaO4 was measured by adiabatic (9–346 K) and differential scanning (316–1336 K) calorimetries. The temperature dependences of entropy, enthalpy change and reduced Gibbs energy of M-DyTaO4 in the range of 0–1273 K were calculated based on smoothed heat capacity values, without taking into account the contribution of phase transformations occurring below 9 K. The general shape of the anomalous Schottky contribution to the molar heat capacity was determined.
Relaxation, adiabatic, and differential scanning calorimetry in the 2–1350 K range of temperatures are used to measure the molar heat capacity of synthesized gadolinium tantalate Gd
3
TaO
7
...characterized via X-ray diffraction, scanning electron microscopy (SEM), and chemical analysis. Such thermodynamic functions of the sample as entropy, the change in enthalpy, and reduced Gibbs energy are calculated. The enthalpy of formation of Gd
3
TaO
7
from elements is determined from literature data. Gadolinium tantalate’s Gibbs energy of formation from oxides in the range of high temperatures is calculated to estimate the stability of gadolinium tantalate relative to its constituent oxides.
Thermodynamic Functions of Terbium Hafnate Guskov, A. V.; Gagarin, P. G.; Guskov, V. N. ...
Russian journal of inorganic chemistry,
06/2021, Letnik:
66, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The molar heat capacity of terbium hafnate with a pyrochlore structure was measured by relaxation and adiabatic calorimetry. The smoothed values of the molar heat capacity were used to calculate the ...thermodynamic functions in the temperature range 6–330 K. The general form of the Schottky anomaly was determined.
Sm3TaO7: Heat Capacity and Thermal Expansion Gagarin, P. G.; Guskov, A. V.; Guskov, V. N. ...
Russian journal of inorganic chemistry,
12/2022, Letnik:
67, Številka:
14
Journal Article
Recenzirano
The molar heat capacity of Sm
3
TaO
7
was determined by relaxation, adiabatic and differential scanning calorimetry in the region of 2–1350 K and the thermodynamic functions were calculated. The ...total contribution of the Schottky anomaly to the heat capacities of samarium tantalate was evaluated. The temperature dependences of the parameters of the orthorhombic crystal lattice of the space group
C
222
1
in the temperature range of 300–1204 K have been determined and the coefficients of thermal expansion have been estimated. The temperature dependence of heat capacity of samarium tantalate exhibits an anomaly in the region of 1116–1275 K associated with the structural phase transition. The space group of the high-temperature orthorhombic phase Sm
3
TaO
7
is identified as
Cmcm
.
Thermodynamic Properties of Sm2Hf2O7 Guskov, A. V.; Gagarin, P. G.; Guskov, V. N. ...
Russian journal of inorganic chemistry,
10/2021, Letnik:
66, Številka:
10
Journal Article
Recenzirano
Pyrochlore samarium hafnate was synthesized by reverse precipitation with final annealing at 1823 K, and identified by X-ray powder diffraction (XRD), chemical analysis, and electron microscopy. ...Relaxation calorimetry and adiabatic calorimetry were used to measure the molar heat capacity in the range 4–347 K. The temperature-dependent entropy, enthalpy increment, and reduced Gibbs energy were calculated. The general form of the Schottky anomaly at low temperatures was determined.
The molar heat capacity of praseodymium hafnate with the pyrochlore structure in the temperature range 2.4–345.6 K was measured by relaxation and adiabatic calorimetry. The thermodynamic functions of ...Pr
2
Hf
2
O
7
were calculated, and the anomalous entropy in the range 0–20 K was estimated. The general form of the anomalous heat capacity at 20–300 K was determined.
Results are presented from measuring the molar heat capacity of the Dy
2
O
3
‧2HfO
2
solid solution in the range of 2.5–346 K. The entropy, enthalpy increment, and reduced Gibbs energy at
T
= ...2.5–1350 K are calculated according to literature data. The general form of the Schottky anomaly is determined.
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