Subsolidus Phase Relations Research Articles

Phase diagram study of Na2O–ThO2–P2O5 system and investigation of thermo physical properties of quaternary compounds

The subsolidus phase relations in Na2O–ThO2–P2O5 pseudo ternary system were determined at 1223 K. Synthesis of all the phases, used for drawing phase diagram, was carried out by solid state route. Formation of ternary and quaternary compounds in Na2O–ThO2, Na2O–P2O5, ThO2–P2O5 and Na2O–ThO2–P2O5 systems was confirmed at 1223 K. With the help of these compounds and phase analysis of number of synthetic mixtures, prepared by reacting different mol fractions of Na2O, ThO2 and P2O5 at 1223 K, phase diagram was drawn and phase boundaries were established. No ternary compound was identified in Na2O–ThO2 system. Formation of three quaternary phosphates, Na2Th(PO4)2, NaTh2(PO4)3 and Na5Th(PO4)3 was confirmed at 1223 K. XRD pattern of monoclinic Na5Th(PO4)3, synthesized for the first time and found iso structural with Na5Th(AsO4)3 and its lattice parameters were obtained by Le Bail method. Thermogravimetric studies of quaternary phosphates were carried out in air to investigate their thermal stability. All the three compounds decompose to ThO2 at 1673 K. Two step weight loss in TG curve of Na2Th(PO4)2 confirmed its decomposition to ThO2 via NaTh2(PO4)3 as an intermediate. To calculate thermal expansion coefficients, high temperature XRD (HT-XRD) data of Na2Th(PO4)2, NaTh2(PO4)3 and Na5Th(PO4)3 was collected in air between the temperature range of 298–1173 K. All these compounds exhibit positive thermal expansion with the average volume expansion coefficient values ranging between 30 and 60 × 10−6 K−1. Heat capacities of these compounds were measured in the temperature range of 308–873 K using Differential Scanning Calorimetry (DSC) technique.

Phase equilibria in the La2O3-Sm2O3-ZrO2 system: Experimental studies and thermodynamic modeling

A series of ceramic samples were prepared to experimentally investigate sub-solidus phase relations in the La2O3-Sm2O3-ZrO2 system at 1873 K and 1673 K. No ternary compounds have been observed, while the binary La2Zr2O7 and Sm2Zr2O7 pyrochlore phases form a continuous solid solution La2−xSmxZr2O7 in the ternary system at the selected temperatures. X-ray diffraction and microstructure results demonstrated that the pyrochlore phase is stable in the ZrO2-rich corner. The homogeneity range of the pyrochlore phase was carefully determined and the phase boundary of the cubic ZrO2 (fluorite phase) which extends into the ternary system was also constructed via electron probe microanalysis. The as-obtained data were adopted to determine the mixing parameters for the pyrochlore and fluorite phases in the present thermodynamic modeling. A self-consistent database of the La2O3-Sm2O3-ZrO2 system was accordingly established for the first time and the calculations agree well with the experimental data in the current work.

Revisiting the Bøggild Intergrowth in Iridescent Labradorite Feldspars: Ordering, Kinetics, and Phase Equilibria

The enigmatic Bøggild intergrowth in iridescent labradorite crystals was revisited in light of recent work on the incommensurately modulated structures in the intermediated plagioclase. Five igneous samples and one metamorphic labradorite sample with various compositions and lamellar thicknesses were studied in this paper. The lamellar textures were characterized with conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The compositions of individual lamellae were analyzed with high-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and atom probe tomography (APT). The average structure states of the studied samples were also compared with single-crystal X-ray diffraction data (SC-XRD). The Na-rich lamellae have a composition of An44–48, and the Ca-rich lamellae range from An56 to An63. Significant differences between the lamellar compositions of different samples were observed. The compositions of the Bøggild intergrowth do not only depend on the bulk compositions, but also on the thermal history of the host rock. The implications on the subsolidus phase relationships of the plagioclase feldspar solid solution are discussed. The results cannot be explained by a regular symmetrical solvus such as the Bøggild gap, but they support an inclined two-phase region that closes at low temperature.

Phase Relations in the Rb2MoO4–R2(MoO4)3–Zr(MoO4)2 (R = Al, Fe, Cr, Y) Systems

Subsolidus phase relations in the Rb2MoO4–R2(MoO4)3–Zr(MoO4)2 (R = Al, Fe, Cr, Y) systems have been studied for the first time by the method of “intersecting cuts.” Eight new triple molybdates, with the compositions Rb5RZr(MoO4)6 (R = Al, Fe, Cr, Y), RbRZr0.5(MoO4)3 (R = Al, Cr, Fe), and Rb2YZr2(MoO4)6.5, have been identified in these systems. The thermal properties and crystallographic characteristics of some molybdates have been assessed.

Subsolidus phase relationship in the Y2O3-Mn3O4-CoOx system in air

The subsolidus phase relations in the Y2O3-Mn3O4-CoOx system in air were investigated by X-ray powder diffraction. All the samples were prepared by solid state reaction method. There are 8 single-phases, 9 two-phase regions and 8 three-phase regions in this system. Two solid solutions, namely o-YCoxMn1-xO3-δ with a narrow range of 0.70 ≤ x ≤ 0.76 and m-YCoxMn1-xO3-δ with a wider range of 0.28 ≤ x ≤ 0.60, were found to form. o-YCoxMn1-xO3-δ crystallizes in an orthorhombic Pnma perovskite structure, while m-YCoxMn1-xO3-δ exhibits diffraction features of either monoclinic P21/n or/and orthorhombic Pnma perovskite structure. The homogeneity ranges for hexagonal YMnO3 (less than 3 at. % CoO), orthorhombic YMn2O5 (less than 4 at. % CoO) and the tetragonal spinel phase t-CoxMn3-xO4 (0-31 at. % CoO), the cubic spinel phase c-CoxMn3-xO4 (65-69 at. % CoO) were determined.

The incommensurately modulated structures of low-temperature labradorite feldspars: a single-crystal X-ray and neutron diffraction study.

Labradorite feldspars of the plagioclase solid solution series have been known for their complicated subsolidus phase relations and enigmatic incommensurately modulated structures. Characterized by the irrationally indexed e-reflections in the diffraction pattern, e-labradorite shows the largest variation in the incommensurate ordering states among the e-plagioclase structures. The strongly ordered low-temperature e-labradorite is one of the last missing pieces of the e-plagioclase puzzle. Nine plutonic and metamorphic labradorite feldspar samples from Canada, Ukraine, Minnesota (USA), Tanzania and Greenland with compositions ranging from An52.5 to An68 were studied with single-crystal X-ray diffraction. Two crystals from Labrador, Canada, and Duluth, MN, USA, with wide enough twin lamellae were analyzed with single-crystal neutron diffraction. The incommensurately modulated structures of e-plagioclase are refined for the first time with neutron diffraction data, which confirmed that the T-O distance modulation in the low-temperature e-plagioclase results from the Al-Si ordering in the framework. Detailed configurations of the M site are also observed in the structures refined from neutron diffraction data, which were not possible to see with X-ray diffraction data. The relation between the q-vectors and the mole% An composition is revealed for the entire compositional range of e-plagioclase, from An25 to An75. The previously proposed two-trend relation depending on the cooling rate and phase transition path is confirmed. A new classification of e-plagioclase (eα, eβ and eγ) is proposed based on the q-vector of the structure, which makes it an independent character from the presence/absence of density modulation. New parameters are proposed to quantify the ordering states of these complicated aperiodic structures of e-plagioclases, such as the difference between 〈T1o-O〉 and 〈T1m-O〉 at phase t = 0.2 or the normalized intensity of the (071\bar 1) reflection.

New triple molybdate K5ScHf(MoO4)6: Synthesis, properties, structure and phase equilibria in the M2MoO4–Sc2(MoO4)3–Hf(MoO4)2 (M = Li, K) systems

Subsolidus phase relations in the M2MoO4–Sc2(MoO4)3–Hf(MoO4)2 (M ​= ​Li, K) systems have been studied by the method of “intersecting cuts”. No new triple molybdates have been identified in the Li2MoO4–Sc2(MoO4)3–Hf(MoO4)2 system and a new triple molybdate K5ScHf(MoO4)6 is formed in the K2MoO4–Sc2(MoO4)3–Hf(MoO4)2 system. The structure of K5ScHf(MoO4)6, have been determined in space group R3‾c through Rietveld analysis of X-ray powder diffraction data. The melting point of molybdate is 999 ​K. The compound has high ion conductivity (about 10−3 ​S ​cm−1).

The Ni–Ni2P phase diagram at 6 GPa with implication to meteorites and super-reduced terrestrial rocks

ABSTRACTWe present experimental results on melting and subsolidus phase relations in the Ni–Ni2P system at 6 GPa and 900–1600°C. The system has four stable phosphides: Ni3P nickelphosphide, Ni8P3/Ni5P2, Ni12P5 and Ni2P transjordanite. The Ni12P5 phase becomes unstable at 900°C and decomposes into Ni5P2 and Ni2P. The eutectic Ni–Ni3P locates at 950°C and 20 mol% P. Ni3P melts incongruently at 1075°C to Ni5P2 and liquid containing 23 mol% P. Ni8P3 and Ni5P2 form a homogeneity range with crystal structure close to Ni5P2. The Ni5P2–Ni2P eutectic locates at 1175°C and 29 mol%. Ni2P melts congruently at 1250°C. The quenched products of nickelphosphide liquid correspond to the eutectics composition and can serve as indicators for reconstructing the P–T–X conditions recorded in meteoritic and terrestrial Fe–Ni–P assemblages. The Ni–P stoichiometries, which were not observed in the equilibrium phase diagrams, including Ni4P and Ni5P, remain enigmatic.

The fate of carbonate in oceanic crust subducted into earth's lower mantle

We report on laser-heated diamond anvil cell (LHDAC) experiments in the FeO–MgO–SiO2–CO2 (FMSC) and CaO–MgO–SiO2–CO2 (CMSC) systems at lower mantle pressures designed to test for decarbonation and diamond forming reactions. Sub-solidus phase relations based on synthesis experiments are reported in the pressure range of ∼35 to 90 GPa at temperatures of ∼1600 to 2200 K. Ternary bulk compositions comprised of mixtures of carbonate and silica are constructed such that decarbonation reactions produce non-ternary phases (e.g. bridgmanite, Ca-perovskite, diamond, CO2–V), and synchrotron X-ray diffraction and micro-Raman spectroscopy are used to identify the appearance of reaction products. We find that carbonate phases in these two systems react with silica to form bridgmanite ±Ca-perovskite + CO2 at pressures in the range of ∼40 to 70 GPa and 1600 to 1900 K in decarbonation reactions with negative Clapeyron slopes. Our results show that decarbonation reactions form an impenetrable barrier to subduction of carbonate in oceanic crust to depths in the mantle greater than ∼1500 km. We also identify carbonate and CO2–V dissociation reactions that form diamond plus oxygen. On the basis of the observed decarbonation reactions we predict that the ultimate fate of carbonate in oceanic crust subducted into the deep lower mantle is in the form of refractory diamond in the deepest lower mantle along a slab geotherm and throughout the lower mantle along a mantle geotherm. Diamond produced in oceanic crust by subsolidus decarbonation is refractory and immobile and can be stored at the base of the mantle over long timescales, potentially returning to the surface in OIB magmas associated with deep mantle plumes.

Subsolidus phase relations and structures of solid solutions in the systems K2MoO4–Na2MoO4–MMoO4 (M = Mn, Zn)

Study of phase formation in the system K2MoO4–Na2MoO4 at 500 °C showed the existence of the only double molybdate K2-xNaxMoO4 (0.4 ≤ x ≤ 1) of the glaserite-related type. Using these data, the subsolidus phase relations in the systems K2MoO4–Na2MoO4–MMoO4 (M = Mn, Zn) were studied at 470–560 °C and the extended solid solutions based on the alluaudite-type Na4−2xM1+x(MoO4)3 were found. In the structure of K1.71Na1.71Mn1.29(MoO4)3 (sp. gr. C2/c, Z = 4, a = 13.0595(3) Å, b = 13.7892(3) Å, c = 7.2973(2) Å, β = 111.339(1)°, R = 0.0134), the potassium ions partially replace Na+ in the channels running along c-axis. The structure of K1.84Na2.11Zn1.02(MoO4)3 (sp. gr. P1̅, Z = 2, a = 7.3258(8) Å, b = 9.4128(10) Å, c = 9.4302(10) Å, α = 93.104(3)°, β = 104.573(3)°, γ = 104.432(3)°, R = 0.0220) is isotypic with alluaudite-related α-K4Zn(WO4)3 and seems to be a result of stabilizing an unknown triclinic modification of K4Zn(MoO4)3 by substitution of sodium for potassium with the strong differentiation of alkali and zinc cations in the structure. In the structure of K1.5Na0.5Mn2(MoO4)3 (sp. gr. Pcca, Z = 8, a = 10.6160(7) Å, b = 12.2714(8) Å, c = 18.0275(11) Å, R = 0.0155) of the α-K2Mn2(MoO4)3 type, one of three initial potassium positions is jointly occupied by (Na, Mn); a similar phenomenon occurs in isostructural Rb3Na3Sc2(MoO4)6. The structure contains zigzag-like ribbons of edge-sharing MnO6 octahedra linked with separate MnO6 octahedra and МоО4 tetrahedra into 3D containing channels along the c-axes filled by K+ ions. BVS maps show possible one-dimensional sodium-ion conductivity for the structures of K1.71Na1.71Mn1.29(MoO4)3 and Rb3Na3Sc2(MoO4)6.

The Fe–Fe2P phase diagram at 6 GPa

ABSTRACTHere, we report experimental results on melting and subsolidus phase relations in the Fe–Fe2P system at 6 GPa and 900–1600°C. The system has two P-bearing compounds: Fe3P and Fe2P. X-ray diffraction patterns of these compounds correspond to schreibersite and barringerite, respectively. The Fe–Fe3P eutectic appears at 1075°C and 16 mol% P. Schreibersite (Fe3P) melts incongruently at 1250°C to produce barringerite (Fe2P) and liquid containing 23 mol% P. Barringerite (Fe2P) melts congruently at 1575°C. Maximum solid solution of P in metallic iron at 6 GPa is 5 mol%. As temperature increases to 1600°C, the P solubility in the metallic iron decreases to 0.5 mol%, whereas the P content in coexisting liquid decreases to 3 mol%. The composition of quenched phases from Fe–P melt coincides with the compositions of equilibrium phases at corresponding temperature. Consequently, the composition of quenched products of Fe-P melts in meteorites can be used for reconstruction of P–T conditions of their crystallization under ambient or low pressures or during shock melting by impact collisions.

Melting and subsolidus phase relations in the system K2CO3–MgCO3 at 3 GPa

ABSTRACTAs part of an investigation of carbonate systems under mantle pressures and temperatures, phase relations in the K2CO3–MgCO3 system have been studied at 3 GPa and 800–1300°C. Subsolidus assemblages comprise the stability fields of K2CO3 + K2Mg(CO3)2 and K2Mg(CO3)2 + MgCO3 with the transition boundary near 50 mol% K2CO3 in the system. The K2CO3–K2Mg(CO3)2 eutectic is located at 840°C and 52 mol% K2CO3. The K2CO3 content in the melt coexisting with potassium carbonate increases to 85 mol% as temperature increases to 1050°C. K2CO3 remains solid up to 1250 and melts at 1300°C. K2Mg(CO3)2 melts incongruently at 890°C to produce magnesite and a liquid containing 51 mol% K2CO3. As temperature increases to 1300°C, the K2CO3 content in the liquid coexisting with magnesite decreases to 27 mol%.

The system K2CO3–CaCO3 at 3 GPa: link between phase relations and variety of K–Ca double carbonates at ≤ 0.1 and 6 GPa

The K2CO3–CaCO3 system is important both in materials science as a source of new nonlinear optical materials and in the Earth science as a sub-system modeling phase relations in fluxing component of mantle rocks responsible for the generation of deep-seated magmas. Existing data on phase relations in the K2CO3–CaCO3 system at ≤ 0.1 and 6 GPa show significant difference in intermediate compounds and, therefore, do not allow any interpolation between these pressures. Here, we report experimental results on melting and subsolidus phase relations in the system K2CO3–CaCO3 at 3 GPa and 800–1285 °C. At 800 °C, the system has two intermediate compounds: K2Ca(CO3)2, synthetic analog of mineral buetschliite, and K2Ca2(CO3)3. As temperature increases to 850 °C, a third intermediate compound, K2Ca3(CO3)4, appears. The calcite–aragonite transition boundary is located at 962 ± 12 °C. Maximum solid solution of CaCO3 in K2CO3 is 18 mol% at 950 °C. The K carbonate–K2Ca(CO3)2 eutectic is established near 970 °C and 56 mol% K2CO3. The melting point of K2CO3 corresponds to 1275 ± 25 °C. K2Ca(CO3)2 melts incongruently at 988 ± 12 °C to produce K2Ca2(CO3)3 and a liquid containing 53 mol% K2CO3. K2Ca2(CO3)3 melts congruently just above 1100 °C. The K2Ca2(CO3)3–K2Ca3(CO3)4 eutectic is situated near 1085 °C and 29 mol% K2CO3. K2Ca3(CO3)4 melts incongruently at 1100 °C to produce calcite and a liquid containing 28 mol% K2CO3. Considering our present results and previous data on the K2CO3–CaCO3 system, a range of K-Ca double carbonates changes upon pressure and temperature increase in the following sequence: K2Ca(CO3)2 (buetschliite), K2Ca2(CO3)3 (≤ 0.1 GPa; < 547 °C) → K2Ca(CO3)2 (fairchildite), K2Ca2(CO3)3 (≤ 0.1 GPa; 547–835 °C) → K2Ca(CO3)2 (buetschliite), K2Ca2(CO3)3, K2Ca3(CO3)4 (ordered) (3 GPa; 800–1100 °C) → K8Ca3(CO3)7, K2Ca(CO3)2 (buetschliite), K2Ca3(CO3)4 (disordered) (6 GPa; 900–1300 °C).

Subsolidus phase relations in a mantle pyroxenite: an experimental study from 0.7 to 1.5 GPa

Subsolidus phase relations in a mantle pyroxenite: an experimental study from 0.7 to 1.5 GPa

Isothermal section of CaO-SiO2-La2O3 system within specific region at 1673–1473 K

So far, the relevant phase equilibrium relations and the type of equilibrium phase fields in the CaO-SiO2-La2O3 basic slag system phase diagram are still unknown, which restricts the smelting process and application in materials of rare earth elements. In the current work, phase equilibrium relations within specific region of CaO-SiO2-La2O3 system at 1673–1473 K were studied experimentally by using the thermodynamic equilibrium experiment followed by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). According to the experimental results, the existence of ternary compound CaO·3SiO2·2La2O3 was determined, it is confirmed to be a solution solid phase. The sub-solidus phase relations between different solid phases were also determined. Finally, the isothermal sections of CaO-SiO2-La2O3 system within specific region at 1673 K, 1573 K and 1473 K were obtained, respectively. The experimental results can not only enrich the phase diagram information of silicate system, but also have practical significance for the application of rare earth in materials.

Subsolidus phase relationships in the Al2O3–SnO2–ZnO ternary system at 1200 °C in air

We report the subsolidus phase relationships in the Al2O3–SnO2–ZnO ternary system at 1200 °C in air. The phases and lattice parameters of samples were analyzed by powder X-ray diffraction (XRD). Only one type of solid solutions was found in this ternary system, which is Al-substituted zinc stannate spinel ternary compounds of Zn2-xSn1-xAl2xO4-type solid solutions with the solubility limit of x ≈ 0.045 at 1200 °C in air. In comparison with In2O3–SnO2–ZnO and Ga2O3–SnO2–ZnO ternary systems previously reported, the solubility limit of Al3+ (≈4.5 mol %) in the Zn2-xSn1-xAl2xO4-type solid solution is much smaller than those of In3+ and Ga3+ in Zn2SnO4 for the substitution of the Sn4+ site, where In3+ and Ga3+ solubility limits are 90 and 100 mol % at 1275 °C and 1250 °C, respectively, in air. In addition, unlike previous report, no solid solution was found to exist more than 0.5 mol% of Zn2+ in Al2O3 at 1200 °C in air. On the basis of our experimental data, we were able to construct the subsolidus phase diagram of the Al2O3–SnO2–ZnO ternary system at 1200 °C in air.

Investigations of the phase relations among e1, e2 and C{\bar {\bf 1}} structures of Na-rich plagioclase feldspars: a single-crystal X-ray diffraction study.

The subsolidus phase relations of plagioclase feldspar solid solution have been puzzling mineralogists and petrologists for decades, mainly due to the complicated structures of intermediate plagioclase at low temperature. The crystal structures of 12 Na-rich plagioclase samples are investigated by single-crystal X-ray diffraction analyses. The samples studied cover a compositional range from An21 to An49 (An is anorthite, CaAl2Si2O8), as well as a wide variety of origins, from extremely slow-cooled gabbroic rocks to pegmatite and metamorphic rocks. The structures fall into three different types: C{\bar 1}, e2 and e1, with an obviously increasing trend in the ordering states of the structures. The phase transitions from C{\bar 1} to e2 and e2 to e1 are both continuous in nature, as no abrupt structure change is required for the transformation. However, the structural difference between C\bar 1 and e1 is large enough to create a miscibility gap causing the Bøggild intergrowth. As the plagioclase structure becomes more and more ordered, Al-Si reorganization in the framework would occur before the ordering of Ca and Na in M sites. Dramatic variations of Na occupancy would only appear in e1 structure with density modulation. This result confirms that Al-Si ordering is the major driving force of the formation of e-plagioclase structure. The composition of the lower end of the Bøggild intergrowth is precisely constrained to An44-An45, based on the structural differences between two samples from the same pegmatite crystal. The modulation periods and directions of e-plagioclase are dependent on the conditions at which e-ordering starts to happen, other than the composition of the plagioclase. However, the three components (δh, δk and δl) of the q vector show strong linear correlations among one another, indicating some crystallographic constraint on the modulation direction which might be independent from the composition. The detailed subsolidus phase relations among e1, e2 and C{\bar 1} are illustrated with a local phase diagram, and schematic free energy curves at different temperatures are provided.

Ab initio-assisted assessment of the CaO-SiO2 system under pressure

We present the results of an ab initio-assisted assessment of melting and subsolidus phase relations in the system CaO-SiO2 up to high pressure conditions. All solid compounds known to nucleate in the system have been treated as purely stoichiometric and the liquid resolved in the framework of a simple polymeric model. Mixing properties of the binary liquid phase are fully described by a single-parameter purely enthalpic chemical interaction plus a strain energy contribution. The latter is required to predict liquid immiscibility of SiO2-rich liquid compositions at ambient conditions and becomes irrelevant at P > 2GPa. A detailed survey of thermodynamic properties of silica polymorphs and calcium oxide and silicates in a broad range of P-T conditions reveals quite controversial stability relations and melting behavior. First-principles calculations on CaO and SiO2 pure liquid components and solid phases (lime and stishovite) have been used, along with a sound assessment of first- and second-order phase transitions, to reconcile thermochemical data with topological details of the observed phase diagrams. A physically-consistent coupling between thermodynamic and thermoelastic properties (viz. compressibility and thermal expansion) turns out to be of fundamental importance to infer reliable stability relations both at subsolidus and melting conditions. Pressure effects shift the composition of the main invariant points in the CaO-SiO2 system and also change the melting behavior of the CaSiO3 metasilicate in a complex manner.

Subsolidus Phase Relations of the CoOx-CuO-SrO System

The subsolidus phase relations of the CoOx-CuO-SrO system were investigated in air. The samples were equilibrated at 900 °C. The pseudo-ternary section contains three stoichiometric binary oxide phases (Sr2CuO3, SrCuO2 and Sr14Cu24O41−δ) and a binary oxide solid solution: Sr6+xCo5O15+δ (0 ≤ x ≤ 0.36). Two binary phases extend into the ternary system forming solid solutions, i.e., Sr14Cu24−xCoxO41−δ (0 ≤ x ≤ 5) and Sr6+xCo5−yCuyO15+δ (0 ≤ x ≤ 0.36, 0 ≤ y ≤ 1.0). The Sr6+xCo5O15+δ solid solution was found to undergo a phase separation into a mixture of Sr6Co5O15−δ and Sr14Co11O33 upon annealing at 600 °C. This transformation is reversible.

Phase relation, structure, and properties of borate MgYB5O10 in MgO–Y2O3–B2O3 system

In the investigation of MgO–Y2O3–B2O3 system, six three-phase regions, five binary compounds, and one ternary compound MgYB5O10 were confirmed in the subsolidus phase relations. Single-phase powder sample of MgYB5O10 was successfully prepared through solution synthesis method. By using the Rietveld method from the step-scanning X-ray powder diffraction data, the crystal structure of MgYB5O10 was determined. It crystallizes in the monoclinic system with the space group P121/c1 and lattice parameters a = 8.5113(2) Å, b = 7.5892(2) Å, c = 12.2460(3) Å, β = 130.200(1)°, and Z = 4. The infrared spectrum of MgYB5O10 at room temperature demonstrates the existence of BO3 and BO4 groups. The UV–visible spectrum shows a wide absorption band within the range of 190–400 nm, while the absorption in the visible region is negligible. According to the electronic structure derived by first-principles calculations, MgYB5O10 is an insulator with a wide indirect energy band gap of about 5.95 eV. Layered structural characteristics, existence of one-dimensional YnO8n+2 chains, and the large band gap should be the immanent reason why MgYB5O10-based materials have exhibited outstanding performances in the luminescence field.