Praseodymium Research Articles

Effects of rare earth ions substitution on the magnetocaloric and critical behavior of La0.6A0.2Sr0.2MnO3 (A=Pr, Nd, Ce) manganite

We have studied the influence of Ce, Pr and Nd elements substitution on the magnetic and magnetocaloric properties of La0.6A0.2Sr0.2MnO3 (A = Pr, Nd, Ce) polycrystalline manganites. X-ray diffraction patterns show that the samples crystallize in the rhombohedral structure with R-3C space group. The Pr and Nd doped samples are single phase, while Ce doped sample has a CeO2 secondary phase. The temperature dependent magnetization exhibits a sharp paramagnetic (PM)–ferromagnetic (FM) transition at 333, 252 and 243 K for Ce, Pr and Nd doped samples, respectively. The results show that the saturation magnetization of the pure and Nd doped samples are higher than Pr doped sample, while the Ce doped sample exhibits lowest magnetization. The magnetic entropy change (ΔSM) was calculated by applying the Maxwell equation and the estimated values in H = 25 kOe were found to be 3.20, 2.63, 3.34 and 3.50 J/kgK for pure, Pr, Nd and Ce doped samples, respectively. Also, improved relative cooling power was observed for the Pr and Nd doped samples. By using three different methods including analyzing magnetization data using Banerjee's criterion, normalizing entropy change versus reduced temperature and using ΔSM(T) data which is related to the local exponent (nL), it is found that all samples display a second-order magnetic phase transition. The critical exponents of the second-order magnetic phase transition for the samples has been calculated, using scaling law and Widom scaling relation and their reliability has also been confirmed with the scaling hypothesis.

Photon-Induced L-Shell X-Ray Production Cross Sections for Lanthanides at 59.54 keV

The Ll, Lα and Lβ X-ray production cross sections for Pr, Nd, Sm, Eu, Gd and Tb elements were determined using a reflection geometry. The excitation was performed with a 241Am radioactive annular source and the L X-rays emitted from targets were counted with a high-resolution Si (Li) detector. The experimental values were compared with other available experimental results and theoretical data. An agreement is observed between the measured and other experimental results or theoretical data.

Cross section measurements of radiative KL2,3 RRS in 24Cr and L3M4,5 RRS in 59Pr for Mn Kα1,2 X-rays

The KL2,3 and L3M4,5 radiative resonant Raman scattering (RRS) cross sections have been measured for the quasimonochromatic Mn Kα1,2 X-rays (5.895keV) in 24Cr (K-shell level width (ΓK) =1.08eV) and 59 Pr (L3-subshell level width (ΓL3) =3.60eV), respectively, using targets in metallic and various chemical forms. The incident Mn Kα1,2 X-ray energy is lower than the K-shell binding energy of 24Cr and L3-subshell binding energy of 59Pr by ~94 ΓK (Cr) and ~94 ΓL3 (Pr), respectively. The experimental measurements were performed with a low energy Ge detector (LEGe) and a radioactive 55Fe annular source in conjunction with 24Cr absorber. The measured cross section values for the 24Cr and 59 Pr elements in their various oxidation states are found to be same within experimental errors. The measurements were further extended to investigate alignment of the intermediate L3-subshell (J =3/2) virtual vacancy states in 59Pr through angular distribution measurements for RRS photon emission, which is found to be isotropic within experimental errors.

Study on the microstructure and properties of low-Ag Sn–0.3Ag–0.7Cu–0.5Ga solder alloys bearing Pr

Effect of Pr element on the wettability, microstructure, interface morphology and mechanical property of Sn–0.3Ag–0.7Cu–0.5Ga–xPr solder has been studied. The result exhibits that the wettability of solders could significantly be improved by adding an approximate amount of Pr, for the forming of well-distributed PrSn3 IMCs could serve as the sites of heterogeneous nucleation, subsequently leading to the refinement of β-Sn matrix and reducing the growth of IMCs. Therefore, the thickness of the IMC layers at the interface (Cu plate/solder) is reduced, implying that the morphology is optimized. The promotion of mechanical properties is also correlated to the refining of IMC layer.

Effect of praseodymium additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3

A series of praseodymium added CeO2(ZrO2)/TiO2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction (XRD), N2-brumauer-emmett-teller (N2-BET), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), PL spectra, Raman spectra, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), respectively. Influence of preparation method on catalytic performance was studied. Results showed that the influence of Pr addition on catalytic performance of the CeO2(ZrO2)/TiO2 catalysts was different between the sol-gel method and the impregnation method. The Pr addition tended to interact with TiO2 and formed the structure of Ti-O-Pr in the sol-gel method while it was more likely to interact with CeO2 forming the structure of Ce-O-Pr in the impregnation method. The total acid amount and redox properties of the catalysts prepared by sol-gel method decreased with the addition of Pr element, which resulted in decrease of catalytic activity. In contrast, the Pr-added catalyst prepared by impregnation method was found to possess easier reducibility, more total acid amount and higher proportion of Ce3+ species, which was favourable for higher catalytic activity.

Simultaneous determination of La, Ce, Pr, and Nd elements in aqueous solution using surface-enhanced laser-induced breakdown spectroscopy

Determination of rare earth elements (REEs) plays an important role in the extraction process. In this work, surface-enhanced laser-induced breakdown spectroscopy (SENLIBS) was introduced to detect REEs (lanthanum, cerium，praseodymium，and neodymium elements) in an aqueous solution. The emission lines of La II 394.91nm, Ce II 418.66nm, Pr II 422.29nm, and Nd II 406.10nm were selected for quantitative analysis by drying the analytical samples on a Zn metal substrate surface and optimizing the experimental parameters. The results showed that the limits of detection (LoDs) for determining La, Ce, Pr, and Nd elements can reach to 0.85, 4.07, 2.97, and 10.98μgmL−1, respectively, which proved that SENLIBS is a feasible method for determining REEs.

Purification of rare earth bis(trifluoromethyl-sulfonyl)amide salts by hydrometallurgy and electrodeposition of neodymium metal using potassium bis(trifluoromethyl-sulfonyl)amide melts

This paper reports a novel bench-scale hydrometallurgical procedure and electrodeposition using potassium bis(trifluoromethyl-sulfonyl)amide (KTFSA) melts for the recovery of rare earth (RE) elements from Nd-Fe-B magnet waste. The investigations were performed at bench scale to assess the potential of a process based on leaching, deironization, and purification of RE amide salts. In the leaching process using 3.4 kg of oxidized Nd-Fe-B and 14.2 L of an aqueous solution of 1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide (HTFSA), 83.0% Nd and 0.98% Fe were leached in 13 h, indicating that selective leaching of RE elements was performed at bench scale. Then, KOH or oxidized Nd-Fe-B was used as a precipitation agent in the deironization process and 100.0% Fe was successfully separated from RE components. Moreover, 4.07 kg of purified amide salts (M(TFSA)3, M = Pr, Nd, Dy, B, Al, and trace elements) were recovered from a spray dryer. The electrochemical behavior of Nd(III) in KTFSA melts containing M(TFSA)3 (molar fraction of RE components: xRE = 0.1) was investigated in this study. Electrochemical analysis revealed that the reduction peak of Nd(III) at around +1.0 V vs. K/K+ was due to the following reaction: Nd(III) + 3e− → Nd(0). The diffusion coefficient of Nd(III) was estimated to be 3.14 × 10−10 m2 s−1 at 483 K by semi-differential analysis, which is similar to that of Nd(III) in KTFSA melts containing pure Nd(TFSA)3 salts (xNd = 0.1). The electrodeposition of Nd was performed under potentiostatic conditions of +0.8 V vs. K/K+ at 483 K. The electrodeposits had a fine surface morphology with small metal particles. The electrodeposits were confirmed to be Nd metal in the middle layer analyzed by scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Finally, we demonstrated the effectiveness of the novel recovery process for practical use by estimating whole material flow.

Effect of Pr3+ doping on structural, electrical, and optical properties of BaTi0.925(Yb0.5Nb0.5)0.075O3 ceramics

The effect of Pr3+ addition on structural, electrical, and optical properties of Ba1−xPr2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 (0.3% ≤ x ≤ 1%) ceramics was investigated. X-ray studies have allowed the identification of a continuous solid solution with P4mm-tetragonal symmetry of all prepared samples. Incorporation of Pr3+ was found to improve ferroelectric and piezoelectric properties with an optimum at the critical concentration of 0.005. Photoluminescence properties revealed that the introduction of Pr3+ ions gives rise to the green and red photoemissions and permitted to shed more light on the created structural disorder and shallow defects. This effect was confirmed by Raman spectroscopy investigation. The presence of Pr element in such materials may have significant technological promise in novel multifunctional devices.

Enhanced magnetoelastic effect in Laves (Tb,Dy)Fe2 alloys with the joint introduction of Pr and Nd

The structural and magnetoelastic properties of (Tb0.3Dy0.7)1−x(Pr0.5Nd0.5)xFe1.93 (0 ≤ x ≤ 0.20) polycrystalline alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain gauge technique. A single (Tb,Dy,Pr,Nd)Fe2 Laves phase with a cubic MgCu2-type structure is formed when x ≤ 0.12, while a small amount of impurities appear when x ≥ 0.15. The easy magnetization direction at room temperature is detected toward axis. The analysis of XRD, magnetization and magnetostriction shows that the Pr and Nd elements joint introduction into (Tb,Dy)Fe2 system can reduce the magnetocrystalline anisotropy and improve the magnetoelastic properties. The (Tb0.3Dy0.7)0.88(Pr0.5Nd0.5)0.12Fe1.93 alloy exhibits a high low-field magnetostriction λa (~314 ppm/1 kOe), a large spontaneous magnetostriction coefficient λ111 (~1710 ppm), a giant saturation magnetostriction λS (~1060 ppm) and the low magnetocrystalline anisotropy at room temperature, and may make it a promising candidate for magnetostriction applications.

A CHARACTERIZATION OF SOME PGL(2, q) BY MAXIMUM ELEMENT ORDERS

In this paper, we characterize some PGL(2,q) by their orders and maximum element orders. We also prove that PSL(2,p) with p > 3 a prime can be determined by their orders and maximum element orders. Moreover, we show that, in general, if q = p n with p a prime and n > 1, PGL(2,q) can not be uniquely determined by their orders and maximum element orders. Several known results are generalized. All groups considered in this paper are finite. For a group G, as in (27), we construct its prime graph ( G) as follows: the vertices are the primes dividing the order of G and two vertices p and r are joined by an edge if and only if G contains an element of order pr. Denote by T(G) = {�i(G)|1 6 i 6 t(G)} the set of all connected components of the graph ( G), where t(G) is the number of the connected components of ( G). If the order of G is even, we always assume that 2 ∈ �1(G). Let

Effect of Pr on phase structure and cycling stability of La–Mg–Ni-based alloys with A2B7- and A5B19-type superlattice structures

Fast capacity degradation is a significant drawback hindering La–Mg–Ni-based alloys from wide application as anode electrode materials of nickel metal hydride batteries. Herein, the effect of Pr element on the phase structure and cycling stability of La0.8−xPrxMg0.2Ni3.4Al0.1 (x=0, 0.1, 0.2 and 0.3) alloys is investigated. All the alloys contain (La,Mg)2Ni7 and (La,Mg)5Ni19 main phases as well as LaNi5 minor phase. It is found that Pr tends to form [AB5] subunits more than [A2B4] subunits, thus increasing the content of (La,Mg)5Ni19 phase with higher [AB5]/[A2B4] ratio in sacrifice of (La,Mg)2Ni7 phase. The increased (La,Mg)5Ni19 phase network with good structural stability increases the anti-pulverization and anti-amorphization resistance of the alloys. After 100 charge/discharge cycles, part of the superlattice phases in La0.6Mg0.2Ni3.4Al0.1 alloy decomposes into amorphous phase and LaNi5 phase, leading to the decrease in superlattce phase abundance; while little amorphization is observed for La0.6Pr0.2Mg0.2Ni3.4Al0.1 alloy and its phase contents remain almost unchanged. Correspondingly La0.6Pr0.2Mg0.2Ni3.4Al0.1 alloy electrode has a slighter oxidation degree after 100 cycles in alkaline electrolyte and exhibits good electrochemical cycling stability with a discharge capacity of 340mAhg−1 and a cycling stability of 90.7% at the 100th cycle.

Influences of Pr and Ta doping concentration on the characteristic features of FTO thin film deposited by spray pyrolysis

The Pr and Ta separately doped FTO (10 at.% F incorporated SnO2) films are fabricated via spray pyrolysis. The microstructural, topographic, optical, and electrical features of fluorine-doped TO (FTO) films are investigated as functions of Pr and Ta dopant concentrations. The x-ray diffraction (XRD) measurements reveal that all deposited films show polycrystalline tin oxide crystal property. FTO film has (200) preferential orientation, but this orientation changes to (211) direction with Pr and Ta doping ratio increasing. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses show that all films have uniform and homogenous nanoparticle distributions. Furthermore, morphologies of the films depend on the ratio between Pr and Ta dopants. From ultraviolet-visible (UV-Vis) spectrophotometer measurements, it is shown that the transmittance value of FTO film decreases with Pr and Ta doping elements increasing. The band gap value of FTO film increases only at 1 at.% Ta doping level, it drops off with Pr and Ta doping ratio increasing at other doped FTO films. The electrical measurements indicate that the sheet resistance value of FTO film initially decreases with Pr and Ta doping ratio decreasing and then it increases with Pr and Ta doping ratio increasing. The highest value of figure of merit is obtained for 1 at.% Ta- and Pr-doped FTO film. These results suggest that Pr- and Ta-doped FTO films may be appealing candidates for TCO applications.

A discontinuous Galerkin method with Lagrange multiplier for hyperbolic conservation laws with boundary conditions

We introduce a discontinuous Galerkin method with Lagrange multiplier (DGLM) to approximate the solution to the hyperbolic conservation laws with boundary conditions. Lagrange multipliers are introduced on the edge/face of the element via weak divergence (Wang and Ye, 2014). The final global system has reduced numbers of unknowns of the standard DG methods. Numerical fluxes from finite volume/difference method are not considered. For the time discretization, backward Euler difference method is used. Stability of the approximate solution is proved in energy norm. Discontinuity of the solution is allowed in the error analysis. Local error estimates of O(hr+12+Δt) with Pr(E) elements (r≥d+12) are derived, where h and Δt are the maximum diameter of the elements and time steps, respectively, and d is the dimension of the spatial domain. The high order approximation is obtained under an appropriate condition on the stabilizing parameter. It is shown that the method preserves the property of the local mass conservation. An explanation on algorithmic aspects is given.

Evaluation of performances of solid oxide fuel cells with symmetrical electrode material

PrxSr0.6Co0.2Fe0.7Nb0.1O3−σ (PxSCFN, x = 0.38, 0.40, 0.42 and 0.44) oxide has been developed as symmetrical electrode material for solid oxide fuel cell (SOFC) in our group. In this study, the effect of Pr element contents on the cell performance of the PxSCFN symmetrical electrode SOFC is investigated in details. Electrochemical impedance spectra (EIS) technique, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used to characterize the electrodes after the performance test. It is found that the nano-sized Co-enriched particles are obviously formed in anode side, which could contribute to the high catalytic activity of the PxSCFN symmetrical electrode materials. An optimum x value, i.e., 0.42, is found for the PxSCFN symmetrical electrode materials. As-prepared single cell shows an average slow degradation rate of 0.5 mV h−1 during 100 h stability test, indicating that the symmetrical SOFC with PSCFN as electrode has the acceptable stabilization. X-ray photoelectron spectroscopy (XPS) analysis indicated that the content of Sr2+ species on the surface decreases to some extent in the case of A-site Pr element slight excess, which could result in the promoting of the catalytic properties of PSCFN material.

New Odd Levels of Pr I with Low Angular Momentum

Ten new odd levels, of praseodymium I (Pr I), having angular momentum less than 3.5, have been discovered through Fourier transform spectroscopy and presented in this paper. The discovered levels not only explain previously known lines, but also explain some new lines of Pr I. All the new levels together explain fifty-six atomic lines. Previously known classifications of two of the lines of Pr are incorrect, new classifications of these lines have been suggested.

Coercivity enhancement in HDDR near-stoichiometric ternary Nd–Fe–B powders

Anisotropic HDDR near-stoichiometric ternary Nd–Fe–B powders have been prepared. The coercivity of the powders was improved from 208.6 to 980.1kA/m by the subsequent diffusion treatment using the Pr–Cu alloy. For comparison, Nd11.5Fe80.7B6.1Pr1.2Cu0.5 alloy, in which Pr and Cu elements were directly added into the original Nd–Fe–B alloy, was also treated by the same HDDR process and the coercivity was only 557.3kA/m. Microstructural investigations showed that a large area of (Nd, Pr)-rich phases concentrated at triangle regions in the HDDR Nd11.5Fe80.7B6.1Pr1.2Cu0.5 powders, while the (Nd, Pr)-rich phases distributed uniformly in the diffusion treated powders. The uniform grain boundary layer can pin the motion of domain wall more effectively, resulting in a higher coercivity in diffusion treated HDDR Nd–Fe–B powders.

Properties of A-site nonstoichiometry (Pr0.4)xSr0.6Co0.2Fe0.7Nb0.1O3−σ (0.9 ≤ x ≤ 1.1) as symmetrical electrode material for solid oxide fuel cells

In order to solve the carbon deposition and sulfur adsorption problems during operations of solid-oxide fuel cells (SOFCs), (Pr0.4)xSr0.6Co0.2Fe0.7Nb0.1O3−σ (PxSCFN, x = 0.9, 0.95, 1.0, 1.05 and 1.1) oxides are synthesized by the solid state reaction method and investigated as both cathode and anode for SOFCs. For PxSCFN (x = 0.9–1.05) powders, it is found that cubic perovskite phase is formed after sintering at 1050 °C; however, when x increases to 1.1, a single impurity phase is detected for P1.1SCFN sample by X-ray diffraction. The effects of A-site nonstoichiometry on thermal expansion coefficient, electrical conductivity and polarization resistance are investigated. The excess of A-site Pr elements in PxSCFN (x = 1.05 and 1.1) results in a decrease in grain size and the creation of more active sites for oxygen reduction reaction. AC impedance reveals that P1.05SCFN as symmetrical electrodes has the best electrochemical catalytic performance both in O2 and in wet H2 atmosphere. The maximum power densities of a P1.05SCFN/LSGM/P1.05SCFN cell reach as high as 1.13 W cm−2 in wet H2 and 0.67 W cm−2 in wet CH4 at 900 °C. Therefore, P1.05SCFN is a potential symmetrical electrode material for SOFCs.

Magnetostriction, composition and microstructure of Tb0.29(Dy1-xPrx)0.71Fe1.97 alloys with heat treatment

Tb0.29(Dy1-xPrx)0.71Fe1.97 (x=0, 0.1, 0.2 and 0.3) alloys prepared by the directional solidification method were treated at 1073, 1123, 1173, 1223 and 1273 K for 4 h for homogenization, respectively. The magnetostriction, micro-morphology and composition distribution were studied by the standard resistance strain gauge technique, optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results indicated that heat treatment could make the microstructure of alloys homogeneous effectively and improve the magnetostriction significantly. The optimum temperature was 1223 K. Compared to the as-cast ones, the increase amplitudes of magnetostriction of the corresponding samples were 39.5%, 64.9%, 95.3% and 50.8% when x=0, 0.1, 0.2 and 0.3, respectively at the compressive stress of 2 MPa and a magnetic field of 80 kA/m. The compressive stress could also improve the magnetostriction. However, further Pr element addition and over high heat treatment temperature would lead to the excessive decomposition of PrFe2 and destroy the homogeneity, resulting in the decline of magnetostriction of alloys.

Structure and electrochemical hydrogen storage characteristics of La0.8−x Pr x Mg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0–0.4) electrode alloys

For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2B7-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The La0.8−xPrxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, (La, Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability (HRD) first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed (x=0.3) alloys generate the largest discharge capacities of 360.8 and 386.5 mA·h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate (S100) at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient (D), the limiting current density (IL) as well as the electrochemical impedance.

Thermochemical properties of the coordination complex of 8-hydroxyquinolinato-bis-(salicylato) praseodymium (III)

The product, [Pr(C7H5O3)2(C9H6NO)], which was formed by praseodymium nitrate hexahydrate, salicylic acid (C7H6O3), and 8-hydroxyquinoline (C9H7NO), was synthesized and characterized by elemental analysis, UV spectra, IR spectra, molar conductance, and thermogravimetric analysis. In an optimalizing calorimetric solvent, the dissolution enthalpies of [Pr(NO3)3·6H2O(s)], [2 C7H6O3(s) + C9H7NO(s)], [Pr(C7H5O3)2(C9H6NO)(s)], and [solution D (aq)] were measured to be, by means of a solution-reaction isoperibol microcalorimeter, \( \begin{gathered}\Updelta_{\text{s}} H_{\text{m}}^{\theta}\left[ {{ \Pr }\left( {{\text{NO}}_{ 3} } \right)_{ 3} \cdot 6{\text{H}}_{ 2} {\text{O}}\left( {\text{s}} \right), 2 9 8. 1 5{\text{ K}}} \right] \, = - ( 20. 6 6 { } \pm \, 0. 29)\,{\text{kJ}}\,{\text{mol}}^{ - 1} , \hfill \\\Updelta_{\text{s}} H_{\text{m}}^{\theta } \left[ { 2 {\text{C}}_{7} {\text{H}}_{ 6} {\text{O}}_{ 3} \left( {\text{s}} \right) +{\text{ C}}_{ 9} {\text{H}}_{ 7} {\text{NO}}\left( {\text{s}}\right),{ 298}. 1 5 {\text{ K}}} \right] \, = \, ( 4 2. 2 7 { }\pm \, 0. 3 1)\,{\text{kJ}}\,{\text{mol}}^{ - 1} , \hfill \\\Updelta_{\text{s}} H_{\text{m}}^{\theta } \left[ {{\text{solutionD }}\left( {\text{aq}} \right), 2 9 8. 1 5 {\text{ K}}} \right] \,= - \left( { 8 9. 1 5 { } \pm \, 0. 4 3}\right)\,{\text{kJ}}\,{\text{mol}}^{ - 1} , \hfill \\\end{gathered} \) and \( \Updelta_{\text{s}} H_{\text{m}}^{\theta } \left\{ {\left[ {{\Pr }\left( {{\text{C}}_{ 7} {\text{H}}_{ 5} {\text{O}}_{ 3} }\right)_{ 2} \left( {{\text{C}}_{ 9} {\text{H}}_{ 6} {\text{NO}}}\right)} \right]\left( {\text{s}} \right),{ 298}. 1 5 {\text{ K}}}\right\} \, = - \left( { 4 1.0 4 { } \pm \, 0. 3 3}\right)\,{\text{kJ}}\,{\text{mol}}^{ - 1} \), respectively. Through an improved thermochemical cycle, the enthalpy change of the designed coordination reaction was calculated to be \(\Updelta_{\text{r}} H_{\text{m}}^{\theta} = \, ( 2 1 3. 1 8\pm0. 6 9)\,{\text{kJ}}\,{\text{mol}}^{ - 1} \), the standard molar enthalpy of the formation was determined as \( \Updelta_{\text{f}} H_{\text{m}}^{\theta} \left\{ {\left[ {{\Pr }\left( {{\text{C}}_{ 7} {\text{H}}_{ 5} {\text{O}}_{ 3} }\right)_{ 2} \left( {{\text{C}}_{ 9} {\text{H}}_{ 6} {\text{NO}}}\right)} \right]\left( {\text{s}} \right), 2 9 8. 1 5 {\text{K}}}\right\} \, = \, - \, ( 1 8 7 5. 4\pm 3.1)\,{\text{kJ}}\,{\text{mol}}^{ - 1} \).