Congruent Melting Research Articles

Ultrahigh‐Temperature Anatexis of Metapelites Generates Near‐Anhydrous Garnet Granitoids

AbstractIt remains unresolved whether extensive granitoids can originate from ultrahigh‐temperature crustal anatexis beyond the stability of fusible hydrous minerals and, if any, how they are generated and characterized. Here we investigate near‐anhydrous garnet granitoids in the Jining Complex, North China, using bulk‐rock and mineral analyses combined with phase equilibria modeling. The Jining garnet granitoids are parautochthonously emplaced within granulite terranes and diagnostically contain perthite, abundant garnet but minor biotite. The rocks exhibit high maficity (FeOT + MgO) of 4–12 wt.%, minimal H2O contents below ∼0.16 wt.% and limited aluminum saturation indexes within 1.1–1.7. Their magmas are scarcely fractionated and have ultrahigh temperatures of 1000–1100°C as revealed by K‐feldspar rich in anorthite (10–13 mol.%) and Ti (175−276 ppm), and garnet rims depleted in heavy rare‐earth elements that crystallize from melts. Besides, these magmas have deficient H2O contents (<∼0.19 wt.%) and high densities and viscosities. The garnet granitoids are generated by metapelite anatexis at ultrahigh‐temperature conditions likely around ∼1100°C, with selective entrainment of 5–40 vol.% residua, and underwent some melt loss during magma crystallization. The melting temperatures are far beyond biotite stability and close to the crustal dry solidus. Garnet‐involved congruent melting reactions are required to produce the maficity‐rich and H2O‐deficient melts with high capability for entraining residua. The ultrahigh‐temperature garnet granitoids differ from ordinary low‐ and high‐temperature garnetiferous granites in both petrologic features and petrogenesis, and represent a new subcategory of S‐type granitoids. They can indicate mantle‐actuated extreme crustal thermal perturbations.

PHASE EQUILIBRIA IN THE SECTION Cu2Se – Cu3SbSe4

Complex selenides are promising thermoelectric materials in a wide temperature range. Since one of the methods for improving material parameters is the formation of solid solutions, the study of phase equilibria and the determination of the homogeneity regions of the components is relevant. This paper presents the results of a study of the physico-chemical interaction in the CuSe2 – Cu3SbSe4 system. The synthesis of alloys of the CuSe2 – Cu3SbSe4 system (0; 10; 30; 50% 70; 90; 100 mol. % Cu3SbSe4) was carried out by a direct one-temperature method at a maximum synthesis temperature of 1053 K. The obtained alloys were studied by X-ray phase, differential thermal and microstructural analyses. Based on the results of the analyses, it was found that CuSe2 – Cu3SbSe4 system is a partially quasi-binary section of the quasi-ternary Cu2Se–Sb2Se3–Se system. The section of CuSe2 – Cu3SbSe4 is characterized by the passage of four nonvariant processes. The studied section crosses the region of primary crystallization of the phase with congruent melting character - β-Cu2Se and the miscibility gap in liquid phase. The region of boundary solid solutions based on the initial components CuSe2 and Cu3SbSe4 does not exceed 5 mol.%.
 Keywords: selenides; phase diagram; thermal analysis; phase equilibria.

Intermetallic compounds RE10RuAl3 (RE = Gd, Tb, Dy, Ho, Er, Tm): Synthesis, crystal structure and thermal properties

In the RE-Ru-Al systems, in the region with high content of rare earth elements a number of isostructural compounds RE10RuAl3 (RE = Gd, Tb, Dy, Ho, Er, Tm) were identified. The structures of the obtained compounds belong to ordered variant of anti-Co2Al5-type with a hexagonal cell, space group P63/mmc (No. 194), Pearson symbol hP28, Z = 2, the cell parameters a = 9.5901(19) Å, c = 9.6504(17) Å (Gd); a = 9.5029(17) Å, c = 9.5746(20) Å (Tb); a = 9.4761(17) Å, c = 9.5544(13) Å (Dy); a = 9.4235(9) Å, c = 9.5132(7) Å (Ho); a = 9.3967(6) Å, c = 9.4761(5) Å (Er); a = 9.3589(12) Å, c = 9.4277(10) Å (Tm). All compounds were synthesized by arc-melting the stoichiometric quantities of elementary components. The structures were determined by X-ray diffraction analysis of a single crystal and refined by the Rietveld method from powder X-ray diffraction patterns. In the structure of the compound Ho10RuAl3 one of the three holmium sites - Ho3 - was mixed with Al, which is reflected in the composition of the intermetallide: compound with Ho shows a small deviation from composition RE10RuAl3 and an adequate formula of the compound is Ho10‒xRuAl3+x (x = 0.07). The crystal structure of the compounds can be represented as rows of trigonal prisms with rare earth atoms at the vertices, centered by ruthenium atoms, alternating with a pair of empty octahedra of rare earth atoms along the direction c of the unit cell. Rows of prisms and octahedrons separate distorted icosahedrons RE[Al6RE6] with a rare earth atom in the center, connected by common triangular faces. All obtained compounds have a congruent melting pattern.

Chemistry in the Molten State: Opportunities for Designing and Tuning the Emission Properties of Halide Perovskites.

A series of monolayered lead halide hybrid perovskites (HO2C(CH2)n-1NH3)2PbX4, named (Cn)2PbX4 (n = 4-6, X = Cl, Br), exhibiting a low congruent melting temperature (Tm) (Tm = 130 °C for (C4)2PbBr4), high stability in the molten state, and whitish type emission, are reported. From the synthesis in the molten state, rare solid solutions of mixed organic cations (Cn1-xCn'x)2PbX4 (n, n' = 4-6; X = Cl, Br; 0 ≤ x ≤1) as well as solid solutions of mixed halides (Cn)2Pb(X1-yX'y)4 (n = 4-6; X, X' = Cl, Br; 0 ≤ y ≤1) have been prepared and characterized (thermal behavior, powder X-ray diffraction (PXRD), photoluminescence properties). The impact of substitutions is significant on the thermal properties, lowering the Tm down to 100 °C for (C4)2Pb(Br0.25Cl0.75)4. The emission properties are slightly tuned in the case of mixed organic cation systems, whereas modifications are more dramatic in the case of mixed halide systems, leading to emission properties through the entire visible region. These results illustrate the great opportunities offered by the congruent melting properties of halide perovskites allowing syntheses in the molten state.

Phase transition and thermodynamic properties of CaV2O6 at high temperature

CaV2O6 is widely utilized in optoelectronic materials, dielectric ceramics, magnetic candidates, and catalytic materials due to its unique physical and chemical properties. CaV2O6 was synthesized by a conventional solid-state reaction technique in this study. The CaV2O6 crystallizes in a monoclinic system belonging to space group C2/m, with the lattice parameters of a = 10.06 Å, b = 3.675 Å, c = 7.039 Å, and β = 104.843°. The congruent melting of CaV2O6 was detected at 1045 K by performing DSC. Enthalpy increments of CaV2O6 were experimentally measured for temperatures ranging from 573 K to 1023 K employing drop calorimetry for the first time. The temperature dependence of the molar heat capacity of CaV2O6 was then calculated on the basis of the enthalpy increments results. Thermodynamic properties (enthalpy change, entropy, and Gibbs free energy) were also calculated in the temperature range of 300–1000 K.

Li2RbSO4Cl with a Short Ultraviolet Absorption Edge and an Acentric Structure through Assembling Heteroleptic [LiO3Cl] Tetrahedra.

Currently, short-wavelength nonlinear optical materials are urgently needed. Through substituting homoleptic [LiO4] in centrosymmetric LiRbSO4 with heteroleptic [LiO3Cl] tetrahedra, an acentric sulfate chloride, Li2RbSO4Cl, was designed and synthesized by the high-temperature melting method. Li2RbSO4Cl shows a relatively short ultraviolet absorption edge (<200 nm) among newly reported sulfate chlorides. Millimeter-sized crystals were grown due to the congruent melting behavior and high thermal stability of the compound.

A practical correlation equation for solubility of hydrates

A practical equation to correlate solubilities of hydrates (Am·nH2O) in water was proposed, and its practicality was examined by analyzing the data of binary aqueous inorganic and organic systems. The derived equation is expressed as ln f(x,m,n) = a + b T−1 + c ln T in which f(x,m,n) stands for xm(1-x)n(m + n)(m+n)/mm/nn where x is the solution composition of A in mole fractions and a, b and c are constants related to physical properties of the hydrate. The equation includes the case of n = 0. After demonstrating its effectiveness by applying it to two cases, solubilities of hydrates were correlated to show acceptable results and in particular the calculated congruent melting points agreed well with the literature data.

Pervasive shock melting at &gt;65 GPa in a Martian basalt, the shergottite Northwest Africa 14672

AbstractShergottites have provided abundant information on the volcanic and impact history of Mars. Northwest Africa (NWA) 14672 contributes to both of these aspects. It is a vesicular ophitic depleted olivine–phyric shergottite, with average plagioclase An61Ab39Or0.2. It is highly ferroan, with pigeonite compositions En49‐25Fs41‐61Wo10‐14 like those of basaltic shergottites, for example, NWA 12335. Olivine (Fo53‐15) has discrete ferroan overgrowths, more ferroan when in contact with plagioclase than when enclosed by pyroxene. The pyroxene (a continuum of augite, subcalcic augite, and pigeonite) is patchy, with ragged “cores” enveloped or invaded by ferroan pyroxene. Magma mixing may be responsible for capture of olivine and formation of pyroxene mantles. The plagioclase is maskelynite‐like in appearance, but the original laths were (congruently) melted and the melt partly crystallized as fine dendrites. Most of the 14% vesicles occur within plagioclase. Olivine, pyroxene, and ilmenite occur in part as fine aggregates crystallized after congruent melting with limited subsequent liquid mixing. There are two fine‐grained melt components, barred plagioclase with interstitial Fe‐bearing phases, and glass with olivine dendrites, derived by melting of mainly plagioclase and mainly pyroxene, respectively. Rare silica particles contain coesite and/or quartz, and silica glass. The rock has experienced &gt;50% melting, compatible with peak pressure &gt;~65 GPa. It is the most highly shocked shergottite so far, at shock stage S6/7. It may belong to the group of depleted shergottites ejected at ~1 Myr from Tooting Crater.

A framework to predict binary liquidus by combining machine learning and CALPHAD assessments

Knowledge of the liquidus is important for the design and processing of many materials. For instance, deep eutectics are important for the design of metallic glasses, and recently multi-principal element alloys have been designed based on eutectic compositions or melting temperatures extrapolated from binary liquidus data. In this study, we provide a general framework for predicting binary liquidus only from the properties of the pure elements and thermodynamic properties calculated by Miedema’s model. Our framework combines three machine learning models that are trained and evaluated on liquidus data collected from 466 CALPHAD assessments of binary phase diagrams. The first model predicts the formation of liquid miscibility gaps with a prediction accuracy of 95.3%, outperforming the empirical Mott model. The second and third models predict the equilibrium onset temperature of solidification and the critical temperature of liquid miscibility gaps, respectively. An important feature of our models is that they can give indications of the presence of congruent melting phases and eutectics. Using our framework, we predict the liquidus in 1563 binary systems not included in our CALPHAD dataset, many of which are unknown. By collecting more data, our framework will continue to grow towards better liquidus prediction.

A thermal modelling of triple tube heat exchanger using phase change material

This paper contains a numerical investigation comparing a series of data for the application of energy storage using a triple tube heat exchanger. The main objective is to study the effect of free convection for a uniform melting in a certain thickness of phase change material (PCM). In addition to that, a non-dimensionless parametric study has been conducted to evaluate the effect of thermal behaviour with the change of the parameters. In this study, the main focus has been kept on studying the effect of inlet temperature and inlet velocity of the heat transfer fluid (HTF) which is described by Stefan number (Ste) and Reynolds number (Re) respectively. The result obtained from the analysis showed that, inlet temperature has a direct impact on achieving uniform melting and lesser melting time however inlet velocity has no such effect on that due to dominant effect of free convection. The vertical orientation of the heat exchanger was also found helpful towards congruent melting as it is influencing the buoyancy force and created a motion in the PCM region.

Investigation of the intermetallic phase stabilities and phase equilibria in Cu-Co-Sm system. Part 1: Cu-Sm system

The binary Cu-Sm system is one of the basic sub-systems, necessary for the development of the materials used as permanent magnets. Nonetheless, there can be found numerous inconsistencies in the phase equilibria data for the system. The current work deals with the evaluation of the phase stabilities of the intermetallic phases in the system and phase equilibria in the Cu-Sm system with the DTA, SEM/EPMA and XRD methods. Cu6Sm and Cu5Sm have been found to express some homogeneity ranges. It was confirmed that CuSm is forming by a peritectic reaction, rather than by congruent melting. The updated phase equilibria data was summed up in a new version of the Cu-Sm phase diagram. The hardness of the Cu6Sm phase was found to be 335 ± 29 HV.

STUDY OF TECHNOLOGICAL PARAMETERS OF OBTAINING CELSIANE AND SLAWSONITE CERAMICS USING SINGLE-STAGE TECHNOLOGY

On the basis of the RO–Al2O3–SiO2 system, radiotransparent ceramic materials of cordierite, celsian, and anorthite composition, which have low dielectric characteristics, are obtained. These requirements are met by one of the main phases of the BaO–Al2O3–SiO2 system – celsian (BaAl2Si2O8), the melting point of which is 1740 °C, and the beginning of active phase formation occurs at a processing temperature of 1300 °C, as well as one of the main phases of the SrO–Al2O3–SiO2 is slavsonite (SrAl2Si2O8), which undergoes congruent melting at a temperature of 1765 °C, and the beginning of active phase formation occurs at a processing temperature of 1400 °C. The purpose of the work is to study the technological parameters of obtaining celsian and slavsonite ceramics by one-stage technology. According to the subsolidus structure of the three-component system RO–Al2O3–SiO2 (RO = ВаО, SrO), it is advisable to synthesize the necessary phases from pure raw materials and, taking into account the presence of impurities that impair the dielectric characteristics, the synthesis of the necessary crystalline phases is carried out from technical raw materials. Figurative points of the compositions of the selected compounds correspond to their stoichiometric composition (for slavsonite, wt. %: SrO – 31,99; Al2O3 – 30,93; SiO2 – 37,08; for celsian, wt. %: BaO – 40,85; Al2O3 – 27,17; SiO2 – 31,98). It was established that the physical characteristics of the obtained samples improve with an increase in the firing temperature by 100 °C, but they are far from the desired level. The dielectric characteristics of the obtained materials are within the requirements for radio-transparent materials. Taking into account the investigated physical properties and the obtained radiographs of fired samples in order to obtain a densely sintered material, it was decided to investigate model compositions with the addition of intensifying additives and to study their influence on the properties of fired samples

Structure and Characterization of K2Na3B2P3O13, a New Nonlinear Optical Borophosphate with One-Dimensional Chain Structure and Short Ultraviolet Cutoff Edge.

Nonlinear optical (NLO) crystals, being the primary medium for laser wavelength conversion, are crucial in all-solid-state lasers. Borophosphates offer more structural varieties than pure borates and phosphates, and they have become popular as NLO crystal candidates. Through spontaneous crystallization, we acquired a noncentrosymmetric alkali metal borophosphate crystal material, K2Na3B2P3O13 (KNBPO). KNBPO crystallizes in the orthorhombic Cmc21 space group with the following unit cell parameters: a = 13.9238(18) Å, b = 6.7673(8) Å, c = 12.1298(15) Å, and Z = 4, and its structure is characterized by a fundamental building unit 1∞ [B2P3O13] chain structure made up of bridging oxygen linkages between BO4 and PO4 tetrahedra. KNBPO has a short ultraviolet (UV) cut-off edge (<186 nm), a congruent melting characteristic, good thermal stability, and a moderate second harmonic generation response roughly 0.42 times that of KH2PO4. Theoretical calculations reveal that the optical properties of the compound mainly originate from BO4 and PO4 units. Due to the short UV cut-off edge, KNBPO can be used as a potential NLO material in the UV and even deep UV regions, and it enhances the structural variety of borophosphates, which has a reference value for scholars investigating similar materials.

Investigation of the solid/liquid phase transitions in the U–Pu–O system

Mixed oxides of uranium and plutonium U1-yPuyO2-x are currently studied as reference fuel for Sodium-cooled Fast Reactors (SFRs). To predict the margin to fuel melting, an accurate description of both solidus and liquidus temperatures of these materials is crucial. In this work, after a critical review of the literature data, the parameters of the liquid phase of the CALPHAD models of the Pu–O and U–Pu–O systems are reassessed based on the model of Guéneau et al.. A good agreement between the calculated and selected experimental data is obtained. Using this model, the melting behaviour of U1-yPuyO2±x oxides is then studied as a function of plutonium content and oxygen stoichiometry. The congruent melting for the mixed oxides is found to be shifted towards low O/M ratios compared to the end-members (UO1.97 and PuO1.95). The temperature of this congruent melting is nearly constant (3130–3140 K) along a ternary phase boundary from UO1.98 to U0.55Pu0.45O1.82 and then decreases with Pu content to a maximum of approximately 3040 K for PuO1.95. This observation is explained by the stabilisation of the hypo-stoichiometric mixed oxides due to the increase of the configurational entropy at high temperatures by the formation of oxygen vacancies and related cation mixing. The influence of the atmosphere used in the laser heating melting experiments on the oxygen stoichiometry of the sample and its solidus and liquidus temperatures is investigated. The determination of this O/M ratio after laser melting tests using XANES is also reported. The simultaneous presence of U6+, U5+, U4+, Pu3+ and Pu4+ is observed, highlighting the occurrence of charge compensation mechanisms. The samples are highly oxidised in air whereas close to stoichiometry (O/M = 2.00) in argon. These results are in agreement with the computed solidification paths. This work illustrates the complex melting behaviour of the U1-yPuyO2±x fuels and highlights the need for the CALPHAD method to accurately describe and predict the high-temperature transitions of the U–Pu–O system.

A comprehensive study of the phase segregation of a urea-based phase change material tested under thermal cycling conditions

Eutectic mixtures are used as PCMs due to the possibility to tailor the melting temperatures and mainly because the phase transition occurs at a unique temperature. Eutectic mixtures are assumed to be congruent melting and solidification materials. Compositional segregation has rarely been reported, when have been researched for its use as PCM. However, the previous premise does not always match the observed facts. The presented work aims to deepen the knowledge regarding the use of eutectic mixtures as PCMs and to determine the influence of operation parameters in the eutectic PCMs potential phase segregation.The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. Nevertheless, the eutectic mixture showed an unforeseen segregation phenomenon when it was exposed to repeated melting-solidification cycles using volumes in the scale of grams. As a result, the phenomenon was studied to determine the potential causes. An experimental campaign was performed to study the urea and sodium nitrate eutectic mixture under different conditions: consisting of thermal cycling using representative masses, and subsequently, the segregated materials and obtained samples were analyzed by different techniques (including XRD, HTXRD, and DSC); and the production of samples under different cooling conditions that were analyzed using microscopy (PLM and SEM). The results established a relationship between the operation conditions, with the resulting crystal structures, which explain the phase segregation in the eutectic mixture. A mitigation measure was determined consisting of mechanical stirring.

Microstructure evolution and phase analysis of Sm60Ni40 alloy

The paper investigates the microstructure evolution and phase analysis of the Sm60Ni40 alloy. The arc melted sample retained the high temperature stable (>873 K) Sm7Ni3 and Sm3Ni2 phases along with the congruently melting SmNi phase. Annealing the as-cast sample at 903 K for 100 h stabilized the high temperature stable (873 K − 903 K) Sm3Ni2 phase. Rietveld refinement was performed to resolve the crystal structure of Sm3Ni2 phase and it was observed that Sm3Ni2 phase stabilizes in monoclinic crystal structure (space group: C2/m) with a lattice parameter of a = 13.49 Å, b = 3.75 Å, c = 9.68 Å and β = 106.6°. The Curie temperature of the Sm3Ni2 phase was determined to be ∼ 110 K. The high squareness ratio of 82 % along with high coercivity of 3 T indicates that the Sm3Ni2 phase possess spontaneous uniaxial magnetic anisotropy.

Stabilization of the Polar Structure and Giant Second‐Order Nonlinear Response of Single Crystal γ‐NaAs0.95Sb0.05Se2

AbstractThe dearth of suitable materials significantly restricts the practical development of infrared (IR) laser systems with highly efficient and broadband tuning. Recently, γ‐NaAsSe2 is reported, and it exhibits a large nonlinear second‐harmonic generation (SHG) coefficient of 590 pm V−1 at 2 µm. However, the crystal growth of γ‐NaAsSe2 is challenging because it undergoes a phase transition to centrosymmetric δ‐NaAsSe2. Herein, the stabilization of non‐centrosymmetric γ‐NaAsSe2 by doping the As site with Sb, which results in γ‐NaAs0.95Sb0.05Se2 is reported. The congruent melting behavior is confirmed by differential thermal analysis with a melting temperature of 450 °C and crystallization temperature of 415 °C. Single crystals with dimensions of 3 mm × 2 mm are successfully obtained via zone refining and the Bridgman method. The purification of the material plays a significant role in crystal growth and results in a bandgap of 1.78 eV and thermal conductivity of 0.79 Wm−1 K−1. The single‐crystal SHG coefficient of γ‐NaAs0.95Sb0.05Se2 exhibits an enormous value of |d11| = 648 ± 74 pm V−1, which is comparable to that of γ‐NaAsSe2 and ≈20× larger than that of AgGaSe2. The bandgap of γ‐NaAs0.95Sb0.05Se2 (1.78 eV) is similar to that of AgGaSe2, thus rendering it highly attractive as a high‐performing nonlinear optical material.

Finding a Deep-UV Borate BaZnB4 O8 with Edge-sharing [BO4 ] Tetrahedra and Strong Optical Anisotropy.

The polarization modulation of deep-UV light is an important process that incorporates functionality to selectively respond to light-mater interaction. Typically, optical anisotropy is foremost to the use efficiency of deep-UV birefringent crystals. Herein, a new congruently melting polyborate with extremely large birefringence (Δn(001) =0.14@589.3 nm) and band gap (6.89 eV) is discovered as a high performance birefringent crystal, which breaks the current deadlock of deep-UV polyborates that usually show small birefringence. The rigid tetrahedra, including [ZnO4 ] and edge-sharing [BO4 ] tetrahedra, make all the planar [BO3 ] triangles in the lattice adopt preferential arrangement and thereby lead to an extraordinary large birefringence that is larger than all the deep-UV borates with experimentally measured values. Structural analyses with the additional theoretical calculations were used to study the origin of strong optical anisotropy in BaZnB4 O8 .

LiAlS2: A promising infrared frequency-conversion material with ultrawide band gap and high laser-induced damage threshold

The development of infrared (IR) nonlinear optical (NLO) crystals could foster their wide applications in civil and military fields. Thus, IR NLO materials with a wide band gap, high laser-induced damage threshold, and lack of two-photon absorption are urgently needed. This work reports the comprehensive optical properties of LiAlS2 through systematic experimental characterizations and the first principle study. The results confirmed the congruently melting feature of LiAlS2, type-I phase matching (PM) performance, and its second-harmonic generation (SHG) response (0.2 × AgGaS2 at 2.09 µm). Notably, LiAlS2 shows the widest band gap of 5.13 eV among the selected IR NLO materials and an ultrahigh laser-induced damage threshold about 28 times that of AgGaS2. The structure-property relationship analysis indicates that the [AlS4] tetrahedra determine the optical band gap and primarily contribute to the SHG response. Moreover, the calculated effective SHG coefficient deff, the refractive index dispersion relation, and the shortest PM wavelength are reported. The results of this study indicate that LiAlS2 can be a promising IR NLO material in high-energy laser systems.

Optimization of Preparation Method, Nucleating Agent, and Stabilizers for Synthesizing Calcium Chloride Hexahydrate (CaCl2.6H2O) Phase Change Material

This study investigates improvements in low-cost latent heat storage material calcium chloride hexahydrate (CaCl2.6H2O). Its melting point is between 25 and 28 °C, with relatively high enthalpy (170–190 J/g); however, this phase change material (PCM) shows supercooling and phase separation. In CaCl2.6H2O incongruent melting causes lower hydrates of CaCl2 to form, which affects the overall energy storage capacity and long-term durability. In this work, PCM performance enhancement was achieved by adding SrCl2.6H2O as a nucleating agent and NaCl/KCl as a stabilizer to prevent supercooling and phase separation, respectively. We investigated the PCM preparation method and optimized the proportions of SrCl2.6H2O and NaCl/KCl. Thermal testing for 25 cycles combined with DSC and T-history testing was performed to observe changes in enthalpy, phase transitions and supercooling over the extended period of usage. X-ray diffraction was used to verify crystalline structure in the compounds. It was found that the addition of 2 wt.% of SrCl2.6H2O reduced supercooling from 12 °C to 0 °C compared to unmodified CaCl2.6H2O. The addition of 5 wt.% NaCl or KCl proved to effectively suppress separation and the melting enthalpy achieved was 169 J/g–178 J/g with congruent melting over 25 cycles, with no supercooling and almost no reduction in the latent heat.