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Trimetaphosphimates decompose not only upon heating but also in water. Hydrolysis of trimetaphosphimic acid leads to the formation of diimidotriphosphoric acid by ring opening. Single-crystal structure determination using synchrotron radiation revealed the oxonium salt of the latter acid with double stacks of rod-shaped anions along [001]. Anharmonic displacement parameters were used to model slight disorder of part of the anions. These are interconnected by hydrogen bonds within and between the stacks. Powder X-ray diffraction confirmed phase purity. At temperatures above 120 °C, diimidotriphosphoric acid decomposes into unknown crystalline compounds. It thus seems a promising precursor for the synthesis of oxonitridophosphates at moderate temperatures. Graphical abstract

Easily accessible Cu1.4Ag0.4Bi5.4Se9 features partially occupied Cu atom sites. Increasing Cu mobility leads to significantly decreasing lattice thermal conductivity upon heating and results in a thermoelectric figure of merit zT of up to 0.23.

The narrow band gap semiconductors Bi2Te3 and Sb2Te3 are well known for their room temperature thermoelectric performance. Recently, they were shown to serve as model systems of three-dimensional topological insulators with a bulk band gap and very robust, spin-resolved surface states due to a special band inversion in their periodic bulk. Evidently, it is of interest to investigate the special surface states with a local probe like nuclear magnetic resonance (NMR). However, especially the bulk NMR of these materials shows peculiar and rather unexpected phenomena, e. g., a magnetic field induced deformation of the local charge symmetry and excessive line broadening due to a special internuclear coupling. Here we report a comprehensive account of the room temperature NMR properties of the spin-1/2 nucleus 125Te of single crystalline Bi2Te3 and Sb2Te3. This includes a very unusual spin-lattice relaxation that seems not to be reflected in the NMR shift, as well as an exchange enhanced NMR line broadening.

Multinary transition metal nitrides and oxonitrides are a versatile and intriguing class of compounds. However, they have been investigated far less than pure oxides. The compounds Sc5 P12 N23 O3 and Ti5 P12 N24 O2 have now been synthesized from the binary nitrides ScN and TiN, respectively, by following a high-pressure high-temperature approach at 8 GPa and 1400 °C. NH4 F acts as a mineralizing agent that supports product formation and crystallization. The starting materials ScN and TiN are seemingly an uncommon choice because of their chemical inertness but, nevertheless, react under these conditions. Sc5 P12 N23 O3 and Ti5 P12 N24 O2 crystallize isotypically with Ti5 B12 O26 , consisting of solely vertex-sharing P(O/N)4 tetrahedra forming two independent interpenetrating diamond-like nets that host TM(O/N)6 (TM=Sc, Ti) octahedra. Ti5 P12 N24 O2 is a mixed-valence compound and shows ordering of Ti3+ and Ti4+ ions.

Single‐crystalline domains in intergrown microcrystalline material of the new compounds Ba22.5+x La55−x [Si129N240−x O x ]O3:Ce3+ and Ba25.5+x La77−x [Si170N312−x O9+x ]O4:Ce3+ were identified by transmission electron microscopy (TEM). Precise diffraction data from these domains were collected with microfocused synchrotron radiation so that crystal structure elucidation of the complex disordered networks became possible. They are composed of two different interconnected slabs of which one is similar in both compounds, which explains their notorious intergrowth. The distribution of Ba and La is indicated by the analysis of bond‐valence sums and by comparison with isostructural Sr28.5+x La75−x [Si170N312−x O9+x ]O4. Ce3+ doping leads to yellow luminescence. This is a showcase that highlights the discovery and accurate characterization of new compounds relevant for luminescence applications from heterogeneous microcrystalline samples by exploiting the capability of the combination of TEM and diffraction using the latest focusing techniques for synchrotron radiation., Single‐crystalline domains of microcrystalline intergrown oxonitridosilicate oxides Ba22.5+x La55−x [Si129N240−x O x ]O3 and Ba25.5+x La77−x [Si170N312−x O9+x ]O4 and related Sr analogues were identified by TEM. Diffraction data collected with microfocused synchrotron radiation reveal extraordinarily complex tetrahedra networks. This combination of analytical methods enables the characterization of new luminescent materials in heterogeneous powder samples.

Linarite, PbCuSO4(OH)2, crystallizes as secondary mineral in form of clusters of crystals in Mine du Pradet at Cap Garonne in France. A tiny single crystal was isolated and its structure was refined from synchrotron diffraction data (λ = 0.049592 nm): P121/m1, a = 467.75(2), b = 563.48(4), c = 967.64(5) pm, β = 102.647(5)°, wR = 0.0544, 819 F 2 values and 56 variables. The proton positions were also refined. The Cu2+ cations are located within Cu(OH)2 ribbons and exhibit pronounced Jahn-Teller distortion (d(Cu–O): 2 × 191.9, 2 × 197.3 and 2 × 252.8 pm). The Cu(OH)2 ribbons are condensed with the sulfate tetrahedra and the lead cations. The latter are coordinated to eight oxygen atoms in a slightly anisotropic manner. Calculations of the electron localization function (ELF) of PbO (litharge), PbSO4 (anglesite) and PbCuSO4(OH)2 (linarite) show pronounced lone-pair character for PbO but rather isotropic ELF values around the lead cations in PbSO4 and PbCuSO4(OH)2.

Tetrahedra-based nitrides with network structures have emerged as versatile materials with a broad spectrum of properties and applications. Both nitridosilicates and nitridophosphates are well-known examples of such nitrides that upon doping with Eu2+ exhibit intriguing luminescence properties, which makes them attractive for applications. Nitridosilicates and nitridophosphates show manifold structural variability; however, no mixed nitridosilicatephosphates except SiPN3 and SiP2N4NH have been described so far. The compounds AESiP3 N7 (AE=Sr, Ba) were synthesized by a high-pressure high-temperature approach using the multianvil technique (8 GPa, 1400-1700 °C) starting from the respective alkaline earth azides and the binary nitrides P3 N5 and Si3 N4 . The latter were activated by NH4 F, probably acting as a mineralizing agent. SrSiP3 N7 and BaSiP3 N7 were obtained as single crystals. They crystallized in the barylite-1O (M=Sr) and barylite-2O structure types (M=Ba), respectively, with P and Si being occupationally disordered. Cation disorder was further supported by solid-state NMR spectroscopy and energy-dispersive X-ray spectroscopy (EDX) mapping of BaSiP3 N7 with atomic resolution. Upon doping with Eu2+ , both compounds showed blue emission under UV excitation.

[EN] High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSb2Te4 into the high-pressure phases of its parent binary compounds (alpha-Sb2Te3 and SnTe) above 7 GPa. The internal polyhedral compressibility, the behavior of the Raman-active modes, the electrical behavior, and the nature of its different bonds under compression have been discussed and compared with their parent binary compounds and with related ternary materials. In this context, the Raman spectrum of SnSb2Te4 exhibits vibrational modes that are associated but forbidden in rocksalt-type SnTe; thus showing a novel way to experimentally observe the forbidden vibrational modes of some compounds. Here, some of the bonds are identified with metavalent bonding, which were already observed in their parent binary compounds. The behavior of SnSb2Te4 is framed within the extended orbital radii map of BA(2)Te(4) compounds, so our results pave the way to understand the pressure behavior and stability ranges of other "natural van der Waals" compounds with similar stoichiometry., This work has been performed under financial support from the Spanish MINECO under Project MALTA-CONSOLIDER TEAM network (RED2018-102612-T) and Project FIS2017-83295-P, from Generalitat Valenciana under Project PROMETEO/2018/123. This publication is a product of the "Programa de Valoracion y Recursos Conjuntos de I+D+i VLC/CAMPUS and has been financed by the Spanish Ministerio de Educacion, Cultura y Deporte, as part of "Programa Campus de Excelencia Internacional". Supercomputer time has been provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster. J.A.S. acknowledges a "Ramon y Cajal" fellowship (RYC-2015-17482) for financial support, and E.L.D.S. acknowledges Marie Sklodowska-Curie Grant No. 785789-COMEX from the European Union's Horizon 2020 research and innovation program. We also thank ALBA synchrotron and DIAMOND light source for funded experiments.

The multigram synthesis of K [Fe S ] starting from K S and FeS is presented, and its electronic and magnetic properties are investigated. The title compound obtains a defect variant of the K[Fe Se ] structure type. Dielectric and impedance measurements indicate a dielectric constant of 1120 at 1 kHz and an outstanding ionic conductivity of 24.37 mS cm at 295 K, which is in the range of the highest reported value for potential solid state electrolytes for potassium ion batteries. The Seebeck coeffcient of the n type conductor amounts to amp; 8722;60 amp; 956;V K at 973 K. The mismatch of the measured electrical resistivity and the predicted metal like band structure by periodic quantum chemical calculations indicates Mott insulating behavior. Magnetometry demonstrates temperature dependent, large exchange biasfields of 35 mT, as a consequence of the coexistence of spin glass and antiferromagnetic orderings due to the iron vacancies in the lattice. In addition, the decreasing training effects of 34 in the exchange bias are identified at temperatures lower than 20 K. These results demonstrate the critical role of iron vacancies in tuning the electronic and magnetic properties and a multifunctional material from abundant and accessible elements

Cu2Se is a high ZT material consisting of cheap and earth abundant elements. Its high thermoelectric performance is mainly based on very low thermal conductivity associated with mobile atoms. This comes with the drawback of a critical voltage, over which the material decomposes to elemental copper and a copper-deficient Cu2−xSe phase. Composites of copper selenide with graphite do not enhance the critical voltage significantly as copper selenide is not completely encapsulated by graphite. Thermoelectric properties of pellets of such composites obtained by mixing and pressing Cu2Se powder and graphite flakes are comparable to pristine Cu2Se, but thermal stability increases remarkably. Samples with different grain sizes show that the reproducibility of measurements is worse for larger grains, which in addition lead to inferior thermoelectric performance. Higher graphite contents increase both thermal and electrical conductivity, and an optimum of the thermoelectric figure of merit ZT is observed for fine-grained samples with 4 wt. % graphite.

We present the first nitridic analogs of micas, namely AE Si 3 P 4 N 10 (NH) 2 ( AE = Mg, Mg 0.94 Ca 0.06 , Ca, Sr), which were synthesized under high-pressure high-temperature conditions at 1400 °C and 8 GPa from the refractory nitrides P 3 N 5 and Si 3 N 4 , the respective alkaline earth amides, implementing NH 4 F as a mineralizer. The crystal structure was elucidated by single-crystal diffraction with microfocused synchrotron radiation, energy-dispersive X-ray spectroscopic (EDX) mapping with atomic resolution, powder X-ray diffraction, and solid-state NMR. The structures consist of typical tetrahedra-octahedra-tetrahedra ( T - O - T ) layers with P occupying T and Si occupying O layers, realizing the rare motif of sixfold coordinated silicon atoms in nitrides. The presence of H, as an imide group forming the SiN 4 (NH) 2 octahedra, is confirmed by SCXRD, MAS-NMR, and IR spectroscopy. Eu 2+ doped samples show tunable narrow-band emission from deep blue to cyan (451 - 492 nm).

The oxide materials Ca3Co4O9 and Na2Ca2Nb4O13 were combined in a new ceramic composite with promising synergistic thermoelectric properties. Both compounds show a plate-like crystal shape and similar aspect ratios but the matrix material Ca3Co4O9 with lateral sizes of less than 500 nm is about two orders of magnitude smaller. Uniaxial pressing of the mixed compound powders was used to produce porous ceramics after conventional sintering. Reactions between both compounds and their compositions were thoroughly investigated. In comparison to pure Ca3Co4O9, mixing with low amounts of Na2Ca2Nb4O13 proved to be beneficial for the overall thermoelectric properties. A maximum figure-of-merit of zT = 0.32 at 1073 K and therefore an improvement of about 19% was achieved by the ceramic composites.

We present the first nitridic analogs of micas, namely AESi

The nitridophosphates AEP(8)N(14) (AE=Ca, Sr, Ba) were synthesized at 4-5 GPa and 1050-1150 degrees C applying a 1000 t press with multianvil apparatus, following the azide route. The crystal structures of CaP8N14 and SrP8N14 are isotypic. The space group Cmcm was confirmed by powder X-ray diffraction. The structure of BaP8N14 (space group Amm2) was elucidated by a combination of transmission electron microscopy and diffraction of microfocused synchrotron radiation. Phase purity was confirmed by Rietveld refinement. IR spectra are consistent with the structure models and the chemical compositions were confirmed by X-ray spectroscopy. Luminescence properties of Eu2+-doped samples were investigated upon excitation with UV to blue light. CaP8N14 (lambda(em)=470 nm; fwhm=1380 cm(-1)) and SrP8N14 (lambda(em)=440 nm; fwhm=1350 cm(-1)) can be classified as the first ultra-narrow-band blue-emitting Eu2+-doped nitridophosphates. BaP8N14 shows a notably broader blue emission (lambda(em)=417/457 nm; fwhm=2075/3550 cm(-1)).

The layered compound Sn2.8(4)Bi20.2(4)Se27 exhibits an extraordinarily long‐periodic 150R stacking sequence. The crystal structure contains three different building blocks, which form upon the addition of Sn to a Bi‐rich bismuth selenide. Sn‐doped Bi2 double (“2”) layers similar to those in elemental bismuth, Sn0.3Bi1.7Se3 quintuple (“5”) layers and Sn0.4Bi2.6Se4 septuple (“7”) layers are arranged in a 7525757525|7525757525|7525757525 sequence, which corresponds to a structure with a=4.1819(4) and c=282.64(6) Å in space group R 3‾ m. The structure of a microcrystal was determined using microfocused synchrotron radiation and refined as a formally commensurately modulated structure in (3+1)D superspace (superspace group R 3‾ m(00γ)00), with a trivial basic structure that contains just one atom. The stacking sequence as well as the cation distribution are confirmed by aberration‐corrected scanning transmission electron microscopy (STEM) in combination with chemical mapping by X‐ray spectroscopy with atomic resolution. Stacking faults are not typical but have been observed occasionally., Layering up: 150R‐Sn2.8(4)Bi20.2(4)Se27 exhibits an extraordinarily long‐periodic layered structure with a lattice parameter of c=282.6(6) Å. The structure is built up from three different kinds of slabs, that is, double, quintuple and septuple layers, which has been confirmed by STEM‐HAADF and EDX with atomic resolution.

Barium imidonitridophosphate BaP6N10NH was synthesized at 5 GPa and 1000 degrees C with a high-pressure high-temperature approach using the multianvil technique. Ba(N-3)(2), P3N5 and NH4Cl were used as starting materials, applying a combination of azide and mineralizer routes. The structure elucidation of BaP6N10NH (P6(3), a=7.5633(11), c=8.512(2) angstrom, Z=2) was performed by a combination of transmission electron microscopy and single-crystal diffraction with microfocused synchrotron radiation. Phase purity was verified by Rietveld refinement. H-1 and P-31 solid-state NMR and FTIR spectroscopy are consistent with the structure model. The chemical composition was confirmed by energy-dispersive X-ray spectroscopy and CHNS analyses. Eu2+-doped samples of BaP6N10NH show blue emission upon excitation with UV to blue light (lambda(em)=460 nm, fwhm=2423 cm(-1)) representing unprecedented Eu2+-luminescence of an imidonitride.

The gold-rich intermetallic compounds REAu4Cd2 (RE = La–Nd, Sm) were synthesized from the elements in sealed tantalum ampoules. Their characterization by X-ray powder and single crystal data confirmed the tetragonal YbAl4Mo2 type, space group I4/mmm. The basic building units are Au4 squares (278 pm Au–Au in CeAu4Cd2) and infinite linear cadmium chains (275 pm Cd–Cd in CeAu4Cd2). We exemplarily studied the solid solution CeAu4+ x Cd2− x for x = 0–1 up to CeAu5Cd. Electron diffraction patterns on a CeAu5Cd sample confirm the single crystal data. They give no hint for complete gold-cadmium ordering. Temperature-dependent magnetic susceptibility measurements of CeAu4Cd2, CeAu5Cd, PrAu4Cd2 and NdAu4Cd2 show stable trivalent rare earth ions and give no hint for magnetic ordering above 3 K.

The lanthanum oxonitridophosphate La21 P40 O46 N57 was synthesized by high-pressure metathesis from partially hydrolysed LiPN2 and LaCl3 at 750-950 °C and 7-9 GPa. The combination of transmission electron microscopy (TEM) and diffraction using microfocused synchrotron radiation revealed a monoclinic crystal structure (space group P21 /n, a=14.042(4), b=7.084(3), c=41.404(10) A, β=97.73(3)° and Z=2), which is characterized by loop-branched 21 member single chains of P(O,N)4 tetrahedra that extend along [2 0 1]. These chains are related to the loop-branched dreier single chains with dreier-ring loops in stillwellite (CeBSiO5 ). In La21 P40 O46 N57 , these chains are characterized by a complex long-periodic conformation and exhibit disorder that involves La/N and P split positions. This is an extraordinarily long periodicity with respect to branched single chains of tetrahedra. La21 P40 O46 N57 constitutes the first rare-earth oxonitridophosphate exhibiting a chain structure. Single-crystal data are consistent with electron and powder X-ray diffraction.

In contrast to the solid solution series (LiSbTe2)1-x(GeTe)x, compounds with compositions (NaSbTe2)1-x(GeTe)x are not thermodynamically stable at room temperature, but can be obtained as metastable phases by quenching melts with x ≤ 0.5. For x > 0.5 and in slowly cooled melts, samples are inhomogeneous. Despite the metastability, the lattice parameters of (NaSbTe2)1-x(GeTe)x show a Vegard-like behavior. The limited tendency toward forming solid solutions is due to the fact that the ionic radius of Na+ is much larger than that of Ge2+ or Li+ and thus the lattice parameter of NaSbTe2 (a = 6.32 A) being significantly larger than that of LiSbTe2 (a = 6.11 A). Measurements of transport properties revealed an increasing Seebeck coefficient with increasing GeTe content. Electrical and thermal conductivities of all members of the series (NaSbTe2)1-x(GeTe)x with x ≤ 0.5 are low with ∼15 mS cm−1 and 0.5 W m−1 K−1, respectively, which is consistent with the inherently low electrical conductivity of NaSbTe2. Nevertheless, this model system explains both the low thermoelectric performance of other chalcogenides with high Na contents and the widely recognized potential of Na as doping agent in thermoelectric materials.

Thermoelectric oxide-based multiphase systems gain synergistic properties from different materials. Therefore, multiphase systems based on a thermoelectric oxide, combined with both a polymeric phase (Matrimid) and a highly electrically conducting phase (Ag, carbon black) have been investigated. Compared to single-phase porous Ca3Co4O9, the resulting composite materials showed a decreased electrical conductivity while reaching a high Seebeck coefficient of up to 200 μV/K as well as a 4 times lower thermal conductivity. The strongly enhanced phonon scattering in the multiphase system resulting in low thermal conductivity is an especially interesting concept to design thermoelectric multiphase materials. Additionally, Ioffe plots are revitalized to compare the resulting power factor and thermal properties of the composite materials. The significantly low thermal conductivity due to the heteromaterial interfaces in the composite materials especially underlines the potential of multiphase systems as thermoelectric materials.

Pt(II) and Cu(II) complexes, trans-[PtCl2(7AI3CAH)2] and [CuBr2(7AI3CAH)2]n, containing 7-azaindole-3-carboxaldehyde (7AI3CAH) have been synthesized and investigated by a single crystal X-ray diffraction, vibrational spectroscopy and DFT calculations. In the platinum(II) complex two pyridine nitrogen atoms of the 7AI3CAH ligands and two chloride ligands are coordinated to the central metal atom, in a square-planar trans arrangement. In the polymeric copper(II) complex the coordination geometry is a tetragonal bipyramid (4 + 2), where the in-plane ligands are two pyridine nitrogen atoms of two organic ligands and two trans-bromide ligands. The apical positions of bipyramid are occupied by the two Br ligands from the neighboring units. Thus, the CuBrBrCu double bridge system is formed. Detailed vibrational assignments of the IR and Raman spectra of the Pt(II) and Cu(II) complexes have been made on the basis of the calculated potential energy distributions (PEDs) using B3LYP method. The in vitro antiproliferative activity of trans-[PtCl2(7AI3CAH)2] was studied against different human cancer cell lines. The results have shown that this complex is comparably cytotoxic with cisplatin at the LoVo (colon cancer) and MCF7 (breast cancer) cells, whilst its cytotoxicity is significantly lower against the A549 cells (lung cancer) as compared to cisplatin. However, it is about 8-fold less toxic than cisplatin against a normal fibroblast cell line (BALB/3T3). A study on stability of trans-[PtCl2(7AI3CAH)2] in DMSO solution has been performed by FT-IR (ATR) spectroscopy to predict a possible binding mode of trans-platinum(II) complex with DNA.

Cu9.1Te4Cl3 is a new polymorphic compound in the class of coinage metal polytelluride halides. Copper is highly mobile, which results in multiple order-disorder phase transitions in a limited temperature interval from 240 to 370 K. Mainly as a consequence of thermal transport properties, the compound's thermoelectric figure of merit reaches values up to ZT = 0.15 in the temperature range between room temperature and 523 K. Its structure is closely related to that of Ag10Te4Br3, another coinage metal polytelluride halide, which represents the first p-n-p-switchable semiconductor approachable by a simple temperature change. The title compound outperforms Ag10Te4Br3 in terms of thermoelectric properties by 1 order of magnitude and therefore acts as a link between the class of p-n-p compounds and thermoelectric materials.

Multinary transition metal nitrides and oxonitrides are a versatile and intriguing class of compounds. However, they have been investigated far less than pure oxides. The compounds Sc5P12N23O3 and Ti5P12N24O2 have now been synthesized from the binary nitrides ScN and TiN, respectively, by following a high‐pressure high‐temperature approach at 8 GPa and 1400 °C. NH4F acts as a mineralizing agent that supports product formation and crystallization. The starting materials ScN and TiN are seemingly an uncommon choice because of their chemical inertness but, nevertheless, react under these conditions. Sc5P12N23O3 and Ti5P12N24O2 crystallize isotypically with Ti5B12O26, consisting of solely vertex‐sharing P(O/N)4 tetrahedra forming two independent interpenetrating diamond‐like nets that host TM(O/N)6 (TM=Sc, Ti) octahedra. Ti5P12N24O2 is a mixed‐valence compound and shows ordering of Ti3+ and Ti4+ ions., The oxonitridophosphates Sc5P12N23O3 and Ti5P12N24O2 have been prepared by high‐pressure high‐temperature reactions from the refractory nitrides ScN and TiN, respectively. These reactions were enabled by the addition of NH4F as a mineralizing agent. The crystal structures were elucidated by a combination of SCXRD, BVS calculations and magnetic measurements for Ti5P12N24O2 revealing two distinct crystallographic sites occupied by either Ti3+ or Ti4+, respectively.

[EN] Two anomalous broad bands are usually found in the Raman spectrum of bulk and 2D Te-based chalcogenides, which include binary compounds, like ZnTe, CdTe, HgTe, GaTe, GeTe, SnTe, PbTe, GeTe2, As2Te3, Sb2Te3, Bi2Te3, NiTe2, IrTe2, and TiTe2, as well as ternary compounds, like GaGeTe, SnSb2Te4, SnBi2Te4, and GeSb2Te5. Many different explanations have been proposed in the literature for the origin of the anomalous broad bands in tellurides, usually located between 119 and 145 cm(-1). They have been attributed to the intrinsic Raman modes of the sample, to oxidation of the sample, to the folding of Brillouin-edge modes onto the zone center, to the existence of a double resonance, like that of graphene, or to the formation of Te precipitates. In this paper, we provide arguments to demonstrate that such bands correspond to clusters or precipitates of trigonal Te in the form of nanosize or microsize grains or layers that are segregated either inside or at the surface of the samples. Several mechanisms for Te segregation are discussed and sample heating caused by excessive laser power during Raman scattering measurements is emphasized. Besides, we show that anomalous Raman modes related to Se precipitates also occur in selenides, thus providing a general vision for better characterization of selenides and tellurides by means of Raman scattering measurements and for a better understanding of chalcogenides in general., This work has been performed under financial support from the Spanish Ministry of Science, Innovation and Universities, the Spanish Research Agency (AEI), and the European Fund for Regional Development (FEDER) under grants TEC2017-85912C2-2, RED2018-102612-T (MALTA-CONSOLIDER TEAM network) and PID2019-106383 GB-C42/C43. We are also thankful for financial support from Generalitat Valenciana under grant PROMETEO/2018/123 (EFIMAT). The authors also acknowledge Dr Philipp Urban for performing the synthesis of SnBi2Te4.

Tetrahedra‐based nitrides with network structures have emerged as versatile materials with a broad spectrum of properties and applications. Both nitridosilicates and nitridophosphates are well‐known examples of such nitrides that upon doping with Eu2+ exhibit intriguing luminescence properties, which makes them attractive for applications. Nitridosilicates and nitridophosphates show manifold structural variability; however, no mixed nitridosilicatephosphates except SiPN3 and SiP2N4NH have been described so far. The compounds AESiP3N7 (AE=Sr, Ba) were synthesized by a high‐pressure high‐temperature approach using the multianvil technique (8 GPa, 1400–1700 °C) starting from the respective alkaline earth azides and the binary nitrides P3N5 and Si3N4. The latter were activated by NH4F, probably acting as a mineralizing agent. SrSiP3N7 and BaSiP3N7 were obtained as single crystals. They crystallized in the barylite‐1O (M=Sr) and barylite‐2O structure types (M=Ba), respectively, with P and Si being occupationally disordered. Cation disorder was further supported by solid‐state NMR spectroscopy and energy‐dispersive X‐ray spectroscopy (EDX) mapping of BaSiP3N7 with atomic resolution. Upon doping with Eu2+, both compounds showed blue emission under UV excitation., The first nitridosilicatephosphates are synthesized using high‐pressure high‐temperature reactions. The incorporation of P and Si as well as their occupational disorder in the compounds AESiP3N7 (AE=Sr, Ba) is proven by solid‐state NMR spectroscopy, STEM‐EDX mapping, and single‐crystal diffraction. Eu2+‐doped samples show blue luminescence under irradiation with UV light and therefore expand the range of possible host lattices for luminescent materials.

High pressure X-ray diffraction, Raman scattering, and electrical measurements, together with theoretical calculations, which include the analysis of the topological electron density and electronic localization function, evidence the presence of an isostructural phase transition around 2 GPa, a Fermi resonance around 3.5 GPa, and a pressure-induced decomposition of SnSb

Due to the weak oxidative force of N2 , nitrides are only typically formed with the less electronegative metals. Meeting this challenge, we here present Pb2 Si5 N8 , the first nitridosilicate containing highly electron-affine cations of a metal from the right side of the Zintl border. By using advanced synchrotron X-ray diffraction, the crystal structure was determined from a tiny single crystal of 1×3×3 μm3 in size, revealing a significantly different bonding situation compared to all other nitridosilicates known so far. Indeed, DFT calculations confirm distinct amounts of covalency not only between Pb and N but also between formal Pb2+ cations. Thus, unprecedented cationic Pb2 dumbbells with a stretching vibration at 117 cm-1 were found in Pb2 Si5 N8 , the first representative of a crystallographically elucidated lead nitride, stabilized by high amounts of covalency.

Based on the known linking options of their fundamental building unit, that is the SiN4 tetrahedron, nitridosilicates belong to the inorganic compound classes with the greatest structural variability. Although facilitating the discovery of novel Si-N networks, this variability represents a challenge when targeting non-stoichometric compounds. Meeting this challenge, a strategy for targeted creation of vacancies in highly condensed nitridosilicates by exchanging divalent M2+ for trivalent M3+ using the ion exchange approach is reported. As proof of concept, the first Sc and U nitridosilicates were prepared from α-Ca2 Si5 N8 and Sr2 Si5 N8 . Powder X-ray diffraction (XRD) and synchrotron single-crystal XRD showed random vacancy distribution in Sc0.2 Ca1.7 Si5 N8 , and partial vacancy ordering in U0.5x Sr2-0.75x Si5 N8 with x≈1.05. The high chemical stability of U nitridosilicates makes them interesting candidates for immobilization of actinides.