Hexagonal Space Group P63mc Research Articles

The Family of MII3(TeIVO3)2(OH)2 (M = Mg, Mn, Co, Ni) Compounds—Prone to Inclusion of Foreign Components into Large Hexagonal Channels

MII3(TeIVO3)2(OH)2 (M = Mg, Mn, Co, Ni) compounds crystallize isotypically in the hexagonal space group P63mc (No. 186) with unit-cell parameters of a ≈ 13 Å, c ≈ 5 Å. In the crystal structure, a framework with composition M3(TeO3)2(OH)1.50.5+ defines large hexagonal channels extending along [001] where the remaining OH− anions are located. Crystal-growth studies under mild hydrothermal conditions with subsequent structure analyses on basis of X-ray diffraction methods revealed that parts of other anions present in solution such as CO32−, SO42−, SeO42−, NO3−, Cl− or Br− could partly replace the OH− anions in the channels. The incorporation of such anions into the M3(TeO3)2(OH)2 structure was confirmed by energy-dispersive X-ray spectrometry (EDS) measurements and Raman spectroscopy of selected single-crystals.

Nonstoichiometric Ellenbergerite-Type Phosphates: Hydrothermal Synthesis, Crystal Chemistry, and Magnetic Behavior

We synthesized single crystals of Na0.55Ni6(OH)3(H0.61PO4)4 (I) and polycrystals of (Na, Ni)0.64Ni5.68(OH)3(H0.67PO4)4 (II) with ellenbergerite-like structures using the hydrothermal method. The phases crystallize in the hexagonal space group P63mc with the following unit cell parameters: a = 12.5342(1) Å, c = 4.9470(1) Å, and V = 673.08(2) Å3 for I; a = 12.4708(2) Å, c = 4.9435(2) Å, and V = 665.82(2) Å3 for II; and Z = 2. Their crystal structures are based on a 3D framework built from NiO6 octahedra and PO4 tetrahedra. The difference between I and II lies in the way the structural channels are filled along the [001] direction. These channels accommodate segments of Na- and (Na, Ni)-centered chains of face-sharing octahedra in the structures I and II, respectively. The magnetic susceptibility χ and the specific heat Cp evidence pronounced low-dimensional magnetic behavior at elevated temperatures and the formation of the weakly ferromagnetic long-range order at TNI = 61 K and TNII = 63 K. Analysis of the χ(T) data within both chain and dimer spin models allows the estimation of the leading exchange interaction parameters in the compounds under study.

From Cc to P63mc: Structural Variation in La3S2Cl2[SbS3] and La3OSCl2[SbS3] Induced by the Isovalent Anion Substitution

The first antimony oxychloride sulfide, namely, La3OSCl2[SbS3], has been designed by isovalent anion substitution strategy. It belongs to the polar hexagonal space group P63mc (No. 186) with a = 9.327(5) Å, c = 7.075(5) Å, V = 533.0(5) Å3, and Z = 2. It is composed of three-dimensional (3D) cationic [La3OSCl2]3+ networks hosting covalent [SbS3] molecular anions. The 3D cationic [La3OSCl2]3+ are formed by the one-dimensional (1D) hexagonal columns of corner-shared [(Cl/S)La3] polyhedra propagating along the 63 axis situated in (0,0,z) and [OLa3] trigonal pyramids via corner-sharing. Moreover, the alternating [SbS3] and [OLa3] trigonal pyramids are arranged along the 3-fold axis located at (1/3, 2/3, z), generating a dipole moment component along the c-direction. Another remarkable structural motif is the occurrence of the empty octahedra formed by the disordered Cl/S anions, which further share the face to form 1D chains extending along the 63 axis located at (0,0,z). Interestingly, the occurrence of the isolated [La3SbOS3]4+ cubane-like clusters instead of the “chains of [La3SbOS3]4+” make the title compound distinct from the related La4OCl2S4 featuring common chains of [La4OS3]4+. The preliminary nonlinear optical (NLO) measurement indicates a moderate second-harmonic-generation (SHG) signal (ca. 0.7 × AgGaS2) at 2050 nm laser. Moreover, calculated birefringence for La3OSCl2[SbS3] is ∼0.269 at 2050 nm. In addition, the optical energy gap of 2.5 eV for La3OSCl2[SbS3] was derived, which can be assigned to the charge transition from the highest value of valence band derived dominantly from the of S 3p states to the lowest value of conduction band mainly made up of the Sb 5p and of La 5d states.

Crystal structure of the high-temperature polymorph of C(NH2)3PbI3 and its thermal decomposition

The synthesis of guanidinium lead iodide, C(NH2)3PbI3 (GUAPbI3), was conducted by slow evaporation of the mixture obtained by dissolving PbI2 and C(NH2)3I in acetonitrile. When the evaporation is done at 40 ºC, a yellow needle-like crystals are being formed. The sample was characterized by elemental analysis, density measurements, scanning electron microscopy, thermal analyses, high-temperature X-ray powder diffraction and infrared spectroscopy measurements. The elemental analysis of the obtained crystals confirmed the proposed stoichiometry. The performed thermal analyses showed an endothermic peak associated with structural transition around 160 ºC. On the other hand, the endothermic temperature effects above 300 ºC are accompanied with mass loss and were interpreted as compound degradation. The crystal structure of high temperature polymorph between 160 ºC and 300 ºC was determined using high-temperature powder diffraction data measurements at 280 ºC using simulated annealing technique in order to obtain initial structural model. The structure was refined using the Rietveld method. At temperatures higher than 160 ºC, C(NH2)3PbI3 crystallizes in hexagonal space group P63mc with unit cell parameter a increasing from 9.269 Å to 9.337 Å between 160 ºC and 300 ºC and c parameter increasing from 15.211 Å to 15.287 Å in the same temperature range. The structure consists of PbI6 octahedra couples sharing a common face, linked with corners. Guanidinium cations are situated in the channels between Pb2I9 couples in a manner that the plane of the molecule is perpendicular to the c-axis.

Synthesis and Crystal Structure of Three Ga-rich Lithium Gallides, LiGa6, Li11Ga24, and LiGa2.

Three new binary phases have been synthesized in the Ga-rich part of the Li-Ga system: LiGa6, Li11Ga24, and LiGa2. Their crystal structures and the respective phase formation conditions have been investigated with X-ray single crystal structure refinements, Rietveld refinements of X-ray powder diffraction data, and thermal analyses. They complete the Ga-rich part of the Li-Ga phase diagram together with the reported phases Li6-xGa14 with 2 ≤ x ≤ 3 and LiGa3.42. The compositions of two of the new gallides, LiGa6 and LiGa2, had been predicted in previous thermoanalytical studies, but their crystal structures remained unknown. All three new binary main group compounds adopt new structure types. LiGa6 crystallizes with the trigonal space group R3̅c (No. 167, a = 6.1851(8) Å, c = 23.467(4) Å), Li11Ga24 crystallizes with the hexagonal space group P63mc (No. 186, a = 13.7700(19) Å, c = 23.250(5) Å), and LiGa2 crystallizes with the orthorhombic space group Cmce (No. 64, a = 8.51953(4) Å, b = 14.44163(7) Å, c = 15.29226(7) Å). All phases form air- and moisture-sensitive crystals of bright metallic luster. They can be synthesized starting from the pure elements and taking into account their incongruent melting behavior by adequate tempering sequences derived from differential scanning calorimetry (DSC) studies of the system. Lithium gallides do not form electron-precise Zintl phases. The electronic structures of these polar intermetallic phases combine ionic, covalent, and metallic bonding contributions and have been analyzed by density functional theory (DFT) calculations in the cases of LiGa6 and LiGa2. Measurements of the specific electronic resistivities have also been performed and prove the metallic behavior.

A first Mn member in the struvite morphotropic series, CsMn(H2O)6(PO4): hydrothermal synthesis, crystal structure and interconnections within the family of related phosphates.

Caesium manganese hexahydrate phosphate, CsMn(H2O)6(PO4), was synthesized under hydrothermal conditions. Its crystal structure was determined from single-crystal X-ray diffraction data. The novel phase crystallizes in the hexagonal space group P63mc and represents the first manganese member in the struvite morphotropic series, AM(H2O)6(TO4). Its crystal structure is built from Mn(H2O)6 octahedra and PO4 tetrahedra linked into a framework via hydrogen bonding. The large Cs atoms are encapsulated in the framework cuboctahedral cavities. It is shown that the size of the A+ ionic radius within the morphotropic series AM(H2O)6(XO4) results is certain types of crystal structures and affects the values of the unit-cell parameters. Structural relationships with Na(H2O)Mg(H2O)6(PO4) and the mineral hazenite, KNa(H2O)2Mg2(H2O)12(PO4)2, are discussed.

Synthesis, crystal structure and Raman spectrum of Ba7[BO3]3Br(O1.33F1.33)

Abstract In addition to amorphous material and Ba7[BO3]4−x F2−3x , air and moisture sensitive single crystals of Ba7[BO3]3Br(O1.33F1.33) were formed from H3BO3, Ba(OH)2, BaF2 and BaBr2·2 H2O in alumina crucibles open to the atmosphere at 1300 K for 13 h. Ba7[BO3]3Br(O1.33F1.33) crystallizes in the hexagonal space group P63 mc (no. 186, Z=2) with the lattice parameters a=1118.1(2) and c=723.93(13) pm. The Raman spectrum of the title compounds was also acquired and is compared to literature data.

Crystal Structure, 7Li NMR, and Structural Relationship of Two Rare‐Earth Metal Richer Polar Intermetallics: La15Ge9Li1.50(16) and La7Ge3

Two novel polar intermetallic compounds have been synthesized by a high‐temperature reaction method, and their crystal structures have been characterized by both single‐crystal and powder X‐ray diffractions. La15Ge9Li1 .50(16) crystallizes in the hexagonal space group P63 mc (Z = 2, Pearson code hP52) with nine crystallographically independent sites in the unit cell, and the lattice parameters are a = 15.516(2) and c = 6.895(2) Å. The overall crystal structure can be described as a √3 × √3 × 1 superstructure of the parent compound La5Ge3 adopting the Mn5Si3‐type, and such a superstructure transformation should be attributed to the particular ordering patterns of interstitial Li atoms at the Wyckoff 2a and 2b sites with different occupation factors. La7Ge3 also crystallizes in the hexagonal P63 mc space group (Z = 2, Pearson code hP20) with three La and one Ge non‐equivalent sites in the unit cell. The lattice parameters are a = 10.666(1) and c = 6.357(1) Å. The crystal structure of La7Ge3 shares some similarities with La15Ge9Li1.50(16) and its parent compound La5Ge3, such as the one‐dimensional (1D) zigzag confacial La6 octahedra chains and the 1D zigzag La atomic chains. Theoretical investigations using tight‐binding linear muffin‐tin orbital (LMTO) method provide a comprehensive understanding about electronic structures and chemical bonding of two title compounds based upon density of states (DOS) and crystal orbital Hamilton population (COHP) analyses. The solid‐state 7Li NMR spectrum measurement proves the existence of two independent interstitial Li positions at two distinctive octahedral sites in La15Ge9Li1.50(16).

Synthesis, crystal structure and optical properties of a new nocentrosymmetric borate: Ba7(BO3)3F5

Introduction of the F− anion in the BaO-B2O3 system generates a new noncentrosymmetric (NCS) materials, Ba7(BO3)3F5, with BO3 triangles and the UV cutoff wavelength below 190nm. Ba7(BO3)3F5 crystallizes in the NCS hexagonal space group P63mc with unit-cell parameters a=11.1562(15)Å, c=7.2415(14)Å, Z=2, V=780.5(2) Å3. The calculated band structures and the density of states of Ba7(BO3)3F5 suggest that its direct gap is 4.349eV. It produces SHG intensity about 1/3 times as large as that of KH2PO4 (KDP) and is phase matchable.

Phase Behavior in the LiBH4–LiBr System and Structure of the Anion-Stabilized Fast Ionic, High Temperature Phase

The fast ionic, high temperature (HT) phase of LiBH4 can be stabilized by Br¯ substitution. Lithium borohydride bromide compounds, Li(BH4)1–xBrx, have been synthesized mechanochemically, with and without thermal treatment and the resulting phase behavior determined as a function of composition. Single phase materials exist for 0.29 ≤ x ≤ 0.50 with conductivity 2 orders of magnitude higher than LiBH4 at 313 K. Powder neutron diffraction has been used to resolve the details of the crystal structure of one such compound. These demonstrate that 7Li(11BD4)0.667Br0.333 retains the HT structure (hexagonal space group P63mc, a ≈ 4.2 Å, c ≈ 6.7 Å) from 293 to 573 K. The borohydride bromide exhibits considerable static and dynamic disorder, the latter invoking complex rotational motion of the (BH4)¯ anions.

Na4La2(CO3)5 and CsNa5Ca5(CO3)8: Two New Carbonates as UV Nonlinear Optical Materials

Two nonlinear optical crystal carbonates (Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were successfully synthesized by hydrothermal method, and both of them crystallized in the same noncentrosymmetric hexagonal space group P63mc (No. 186). The structure of Na4La2(CO3)5 consists of a three-dimensional network made up of [CO3] triangles as well as irregular [Na(0.67)La(0.33)O10] and [NaO8] polyhedra. The structure of CsNa5Ca5(CO3)8 can be described as the standing-on-edge [CO3] groups connect the adjacent infinite [CaCO3]∞ layers in the ab plane to construct a framework with four types of channels running parallel to [010]. The Na, Cs, and [Na(0.67)Ca(0.33)] atoms reside in these channels. The measurement of second harmonic generation (SHG) by the method adapted from Kurtz and Perry indicated that Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were phase-matchable in the visible region and exhibited SHG responses of approximately 3 and 1 × KH2PO4 (KDP). Meanwhile, they exhibited wide transparent region with short UV cutoff edge at about 235 and 210 nm, respectively, suggesting that these crystals as NLO materials may have potential applications in the UV region.

Synthesis, crystal structure and magnetic properties of Li2InMo3O8: A novel reduced molybdenum oxide containing magnetic Mo3 clusters

Powder samples and single crystals of Li2InMo3O8 were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction (771 independent reflections for 33 refinable, R1=0.0158 and wR2=0.0354). Li2InMo3O8 is isomorphous with Li2SnMo3O8 and crystallizes in the hexagonal space group P63mc with unit-cell parameters a=5.7931(2)Å, c=10.4681(4)Å and Z=2. The crystal structure consists of distorted hexagonal-close-packed oxygen layers with stacking sequence abac along [001] and that are held together by alternating lithium–indium and molybdenum layers. The Li+ and In3+ ions occupy, respectively, tetrahedral and octahedral sites in the ratio 2:1. The Mo atoms occupy octahedral sites and form strongly bonded triangular clusters involving three MoO6 octahedra that are each shared along two edges, constituting a Mo3O13 unit. The variations of the Mo–Mo and Mo–O bond lengths according to the number of electrons per Mo3 cluster are discussed. The trivalent oxidation state of the indium leads to one unpaired electron per Mo3 and thus gives rise to a paramagnetic spin behavior with an effective magnetic moment of 1.5μB per Mo3 cluster. The magnetic susceptibility vs. temperature curve also shows a maximum at 25K arising probably from an antiferromagnetic ordering between the Mo3 clusters.

Construction of two novel indium phosphites with (3,6)- and (3,5)-connected frameworks: Synthesis, structure and characterization

Two novel anionic indium phosphites, formulated as [H3O][In(HPO3)2] (1) and [C4H12N2][In2(HPO3)3(C2O4)] (2), were prepared under hydrothermal conditions by using piperazine (PIP) as a structure-directing agent (SDA). Single-crystal X-ray diffraction analysis reveals that compounds 1 and 2 crystallize in the hexagonal space group P63mc (No. 186) and orthorhombic space group Cmcm (No. 63), respectively. Compound 1, constructed from InO6 octahedra and HPO3 pseudo-pyramids, exhibits a rare (3,6)-connected layer structure with kgd (Kagome dual) topology. Compound 2, on the other hand, features a 3D phosphite-oxalate hybrid structure with intersecting 8- and 12-MRs channels. From a topological perspective 2 can be regarded as a (3, 5)-connected binodal net with the Schläfli symbol (42.6)(42.65.83).

Syntheses and Crystal Structures of the Solid Solution Sr4OBr2.89(2)Cl3.11(2) and the Elusive Ba2OBr2

Transparent and colorless single crystals of the compounds Sr4OBr2.89(2)Cl3.11(2) and Ba2OBr2 were obtained by solid-state reactions of SrCl2, SrBr2 and SrO (3 : 3 : 2 molar ratio) or by using an excess of BaO together with BaBr2 and Ba as a flux with the molar ratio 3 : 2 : 2, respectively. Ba2OBr2 crystals are isopointal to K2ZnO2 adopting the orthorhombic space group Ibam (no. 72, Z = 4) with the cell parameters a = 7247.44(10), b = 1297.76(20) and c = 657.43(10) pm. Sr4OBr2.89(2)Cl3.11(2) is isotypic to Ba4OCl6 (or isopointal to K6ZnO4) and crystallizes in the hexagonal space group P63mc (no. 186, Z = 2) with the cell parameters a = 982.20(4) and c = 750.41(7) pm.

HoF[SeO3] und Ho3F[SeO3]4: Zwei fluorid‐derivatisierte Oxoselenate(IV) des Holmiums

AbstractHoF[SeO3] and Ho3F[SeO3]4: Two Fluoride‐ Derivatized Holmium Oxoselenates(IV)Three different structure types of rare‐earth metal(III) fluoride oxoselenates(IV) with the formula MF[SeO3] (M = Y, La, Lu) exist so far, whereas for the intermediate lanthanoids M3F[SeO3]4‐type compounds are known with the elements gadolinium and dysprosium. Holmium is now the first lanthanoid realizing both formula types of fluoride oxoselenates(IV), HoF[SeO3] as well as Ho3F[SeO3]4. HoF[SeO3] crystallizes isotypically to YF[SeO3] in the monoclinic system with space group P21/c (a = 657.84(6), b = 688.73(7), c = 718.25(7) pm, β = 99.213(5)° and Z = 4). Ho3+ at the general site 4e is surrounded by six oxide and two fluoride anions forming [HoO6F2]11− polyhedra (d(Ho–O) = 229−244 plus 261 pm, d(Ho–F) = 219 and 221 pm, CN(Ho3+) = 8). Like in YF[SeO3] the $^{2}_{\infty}\rm \{[HoO_{3}F]^{4-}\}$ sheets resulting from condensation of these polyhedra are interconnected by Se4+ cations showing a ψ1‐tetrahedral oxygen coordination as discrete [SeO3]2− anions (d(Se–O) = 167 – 175 pm), but by imaginary removal of the latter only $^{1}_{\infty}\rm \{[HoF^{v}_{2/2}]^{2+}\}$zigzag chains running parallel to the [001] direction remain. Ho3F[SeO3]4 crystallizes in the non‐centrosymmetric hexagonal space group P63mc (a = 1030.24(3), c = 680.37(2) pm and Z = 2). Three [HoO8F]14− polyhedra (d(Ho–O) = 232–254 pm and d(Ho–F) = 233 pm, CN(Ho3+) = 9) at a time are connected via common O2···F edges and four attached ψ1‐tetrahedral [SeO3]2− anions (d(Se–O) = 169–170 pm) to complete the basic building block {FHo3[(Se1)(O1)3][(Se2)(O2)(O3)2]3}. These entities with F−‐centered (Ho3+)3 triangles represent a single formula unit and share triangular (O1,O3,O3) faces with six other blocks in [001] direction. Large hexagonal channels are remaining in between which harbor the “lone‐pair” electrons of the isolated [(Se2)(O2)(O3)2]2− anions. Due to the free position of z/c in space group P63mc, z/c = 1/4 was chosen for the unique fluoride anion on site 2b (site symmetry: 3m.) in order to unify the descriptions for all M3F[SeO3]4‐type compounds eventually. The syntheses of HoF[SeO3] and Ho3F[SeO3]4 succeeded by reacting holmium sesquioxide (Ho2O3), holmium trifluoride (HoF3) and selenium dioxide (SeO2) in molar ratios of 1 : 1 : 3 and 4 : 1 : 12, respectively, with CsBr as fluxing agent within five days at 750 °C in evacuated graphitized fused‐silica ampoules.

Alkaline Earth Metal Oxyhalides Revisited – Syntheses and Crystal Structures of Sr4OBr6, Ba4OBr6 and Ba2OI2

Single crystals of the compounds Ca4OCl6, Sr4OBr6, Ba4OBr6, and Ba2OI2 were obtained by solid-state reactions. The crystals of Ba2OI2 are transparent and colorless and isopointal to K2ZnO2 adopting the orthorhombic space group Ibam (no. 72, Z = 4) with the cell parameters a = 747.20(9), b = 1392.02(18), and c = 678.12(9) pm. Sr4OBr6 and Ba4OBr6 are isotypic to Ba4OCl6 (or isopointal to K6ZnO4) and crystallize in the hexagonal space group P63mc (no. 186, Z = 2) exhibiting the cell parameters a = 982.20(4) and c = 750.41(7) pm for Sr4OBr6 and a = 1030.10(2) and c = 785.92(4) pm for Ba4OBr6. In the ternary systems Ca-O-X (X = Cl, Br or I) the only compound found other than the starting materials was the already known Ca4OCl6 which is also isotypic to Ba4OCl6 crystallizing in the hexagonal space group P63mc (no. 186, Z = 2) with the cell parameters a = 903.30(6) and c = 683.27(8) pm.

The Structure of Ferrihydrite, a Nanocrystalline Material

Despite the ubiquity of ferrihydrite in natural sediments and its importance as an industrial sorbent, the nanocrystallinity of this iron oxyhydroxide has hampered accurate structure determination by traditional methods that rely on long-range order. We uncovered the atomic arrangement by real-space modeling of the pair distribution function (PDF) derived from direct Fourier transformation of the total x-ray scattering. The PDF for ferrihydrite synthesized with the use of different routes is consistent with a single phase (hexagonal space group P6(3)mc; a = approximately 5.95 angstroms, c = approximately 9.06 angstroms). In its ideal form, this structure contains 20% tetrahedrally and 80% octahedrally coordinated iron and has a basic structural motif closely related to the Baker-Figgis delta-Keggin cluster. Real-space fitting indicates structural relaxation with decreasing particle size and also suggests that second-order effects such as internal strain, stacking faults, and particle shape contribute to the PDFs.

The Elusive Tetrasamarium‐oxide‐hexabromide, Sm4OBr6.

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The Elusive Tetrasamarium‐oxide‐hexabromide, Sm4OBr6

AbstractBlack single crystals of tetrasamarium(II)‐oxide‐hexabromide, Sm4OBr6, were obtained from a reaction of SmBr3, Sm2O3 and Na in a sealed tantalum container at 750 °C. Sm4OBr6 crystallizes in the hexagonal space group P63mc (Z = 2, a = 985.89(9), c = 753.50(6) pm, R = 0.035 for all data) as do all M4OX6 type oxide halides with M = Ca,Sr,Ba,Eu,Sm,Yb and X = Cl,Br,I, as far as they have been obtained. The crystal structure is also the anti‐type of K6HgS4/Na6ZnO4 with K6HgS4 = Br6OSm4. The {OSm4} tetrahedron is surrounded by 18 bromide ligands according to {OSm2Sm13}(μ1‐Br16)(μ1‐Br23)(μ2‐Br13)(μ2‐Br23)(μ3‐Br23). These bromide ligands bridge to other such tetrahedra to allow for a three‐dimensional structure.

Synthesis, structure, and luminescence properties of Eu2+ and Ce3+ activated BaYSi4N7

BaYSi4N7 and its phosphors activated with Eu2+ and Ce3+ were synthesized by solid-state reaction at 1400–1650°C under nitrogen mixed with hydrogen atmosphere. The crystal structure of BaYSi4N7 was solved by direct methods and refined by the Rietveld method from powder X-ray diffraction data. BaYSi4N7 crystallizes in the hexagonal space group P63mc (No.186), with a = 6.0550 (2)Å, c = 9.8567 (1)Å, V = 312.96 (2)Å3, and Z = 2, which is isotypic with BaYbSi4N7. The photoluminescence properties have been studied for the solid solutions of Ba1−xEuxYSi4N7 (x = 0–0.4) and BaY1−xCexSi4N7 (x = 0–0.1) at room temperature. Eu2+-doped BaYSi4N7 gives a broad green emission band centered between 503 and 527nm depending on the Eu2+ concentration. The Eu2+ emission band shows a red-shift formulation with increasing Eu2+ concentration mainly caused by the change of the crystal field strength and Stokes shift. Concentration quenching of Eu2+ emission is observed for x = 0.05 due to energy transfer between Eu2+ ions by electric dipole–dipole interactions with a critical interaction distance of about 20Å. Ce3+-doped BaYSi4N7 exhibits a bright blue emission band with a maximum at about 417nm, which is independent of Ce3+ concentration. This is ascribed to a lower solubility of Ce3+ ions in BaYSi4N7 lattice as shown by X-ray powder diffraction analysis.