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The all-solid-state battery (ASSB) is a promising candidate for electrochemical energy storage. In view of the limited availability of lithium, however, alternative systems based on earth-abundant and inexpensive elements are urgently sought. Besides well-studied sodium compounds, potassium-based systems offer the advantage of low cost and a large electrochemical window, but are hardly explored. Here we report the synthesis and crystal structure of K-ion conducting T5 KSi2 P3 inspired by recent discoveries of fast ion conductors in alkaline phosphidosilicates. KSi2 P3 is composed of SiP4 tetrahedra forming interpenetrating networks of large T5 supertetrahedra. The compound passes through a reconstructive phase transition from the known T3 to the new tetragonal T5 polymorph at 1020 °C with enantiotropic displacive phase transitions upon cooling at about 155 °C and 80 °C. The potassium ions are located in large channels between the T5 supertetrahedral networks and show facile movement through the structure. The bulk ionic conductivity is up to 2.6×10-4 S cm-1 at 25 °C with an average activation energy of 0.20 eV. This is remarkably high for a potassium ion conductor at room temperature, and marks KSi2 P3 as the first non-oxide solid potassium ion conductor.

In this paper, we discuss information on crystal structure and morphology available from nuclear magnetic resonance (NMR) spectroscopy of 207Pb for the mineral family [Pb(4f)]2[Pb(6h)]3(AO4)3Cl with A = V (vanadinite), P (pyromorphite), and As (mimetite). The isotropic chemical shift of the 207Pb atoms at Wyckoff positions 4f and 6h was (re-)determined from either static single-crystal or magic angle spinning NMR experiments. This isotropic shift can be linearly correlated to the unit-cell volume within the mineral family, and in the wider context of lead-bearing minerals, to the shortest Pb-O distance for position 4f, in which 207Pb is solely coordinated by oxygen. By evaluating the number of resonances and their respective line widths in the 207Pb-NMR spectra of these three naturally grown minerals, it could be established that vanadinite forms single-domain macroscopic crystals with very small mosaicity, whereas pyromorphite crystals show NMR characteristics, which can be interpreted as being caused by significant mosaicity. In some instances, this mosaic spread could be quantitatively approximated by a Gaussian distribution with a standard deviation angle of σ = 5°. In contrast, our mimetite specimen was composed of multiple sub-crystals with a very high variability of orientations, going beyond mere mosaicity effects. By extending the NMR methodology presented here to other minerals, it may be possible to gain new insights about structure-property relationships and the morphology of natural grown minerals.

We report on the synthesis of the II‐IV‐N2 semiconductors ZnSiN2, MnSiN2, and the Zn1–xMnxSiN2 solid solutions by a one‐step solid‐state metathesis reaction. The successful syntheses were carried out by reacting the corresponding metal halides with stoichiometric amounts of silicon nitride and lithium azide in sealed tantalum ampoules. After washing out the reaction byproduct LiCl, powder X‐ray diffraction patterns were indexed with orthorhombic space group Pna21. Single phase products were obtained without applying external pressure and at a moderate reaction temperature of 700 °C. The resulting ZnSiN2 was found to consist of nano‐sized grains and needle‐shaped nano‐crystals. With increasing manganese content in the Zn1–xMnxSiN2 solid solution, we found the reaction product to be increasingly crystalline. Both the cell parameters and the bandgap values across the different compositions of the solid solutions change linearly. The sample Zn0.95Mn0.05SiN2 synthesized by means of solid‐state metathesis reaction is an intense red emitter with a broad emission maximum at λmax ≈ 619 nm when excited with ultraviolet light after annealing the sample at a pressure of 6 GPa and a temperature of 1200 °C.

The effort for determining NMR interaction tensors from orientation-dependent spectra of single crystals may be greatly reduced by exploiting symmetry relations between atoms of the observed nuclide in the unit cell, as is well documented in the literature. In this work, we determined both the full chemical shift (CS) tensor of 207Pb and the unknown orientation of the rotation axis for the natural mineral phosgenite, Pb2Cl2CO3, from a single rotation pattern, i.e. spectra of crystal orientations from 0 to 180°. In the tetragonal crystal structure of phosgenite, four symmetry-related, but magnetically inequivalent 207Pb are generated by the Wyckoff multiplicity. The mineral wulfenite, PbMoO4, also crystallises in a tetragonal space group, but the site multiplicity for 207Pb generates only one magnetically inequivalent atom, thus not supplying sufficient experimental data to determine CS tensor and axis orientation from an arbitrary number of rotation patterns. One solution to this problem is to simultaneously acquire data of a known compound with high symmetry and Wyckoff multiplicity (here: phosgenite), which supplies additional constraints making the solution of the target compound (here: wulfenite) possible. The 207Pb CS tensors thus determined are characterised by the following eigenvalues in ppm: δ 11 P A S = ( − 2553 ± 1 ) , δ 22 P A S = ( − 1929 ± 1 ) , δ 33 P A S = ( − 1301 ± 1 ) for phosgenite, and δ 11 P A S = ( − 2074 ± 1 ) , δ 22 P A S = ( − 2074 ± 1 ) , δ 33 P A S = ( − 1898 ± 1 ) for wulfenite.

The electronic surroundings of phosphorus and lithium atoms in the ionic conductor lithium dihydrogen phosphate (LDP) have been studied by single-crystal nuclear magnetic resonance (NMR) spectroscopy at room temperature. From orientation-dependent NMR spectra of a large homegrown LDP single crystal, the full 31P chemical shift (CS) and 7Li quadrupole coupling (QC) tensor was determined, using a global fit over three rotation patterns. The resulting CS tensor is characterized by its three eigenvalues: &delta, 11 P A S = ( 67.0 &plusmn, 0.6 ) ppm, &delta, 22 P A S = ( 13.9 &plusmn, 1.5 ) ppm, and &delta, 33 P A S = ( &minus, 78.7 &plusmn, 0.9 ) ppm. All eigenvalues have also been verified by magic-angle spinning NMR on a polycrystalline sample, using Herzfeld&ndash, Berger analysis of the rotational side band pattern. The resulting 7Li QC tensor is characterized by its quadrupolar coupling constant &chi, = Q 33 P A S = ( &minus, 71 &plusmn, 1 ) kHz and the two eigenvalues Q 11 P A S = ( 22.3 &plusmn, 0.9 ) kHz, and Q 22 P A S = ( 48.4 &plusmn, 0.8 ) kHz. The initially unknown orientation of the mounted crystal, expressed by the orientation of the rotation axis in the orthorhombic crystal frame, was included in the global data fit as well, thus obtaining it from NMR data only.

Orientation-dependent NMR spectra of a single crystal of the mineral vanadinite, Pb5(VO4)3Cl, were acquired using only one rotation axis with a general orientation in the hexagonal crystal lattice (space group P 6 3 / m ). The chemical shift (CS) tensors for the 207Pb on Wyckoff positions 6 h and 4 f , and both CS and quadrupole coupling tensor Q for 51V at the positions 6 h were determined by including the NMR response of symmetry-related atoms in the unit cell (and in case of 207Pb at 4 f , also the isotropic shift from MAS NMR spectra). This previously suggested ’single rotation method’ greatly reduces the necessary amount of data acquisition and analysis. The precise orientation of the rotation axis could not be found by X-ray diffraction experiments because of the high linear absorption coefficient of vanadinite, which is chiefly due to its high lead content. The axis orientation was therefore included into the multi-parameter data fit routine. This NMR-based approach is widely applicable, and offers an alternative way of orienting single crystals. The NMR parameters derived from the tensor eigenvalues are δ i s o = ( − 1729 ± 9 ) ppm, Δ δ = ( − 1071 ± 5 ) ppm, η C S = 0.362 ± 0.008 for 207Pb at positions 6 h , and δ i s o = ( − 1619 ± 2 ) ppm, Δ δ = ( − 780 ± 58 ) ppm, η C S = 0.06 ± 0.08 for positions 4 f . For 51V, δ i s o = ( − 509 ± 3 ) ppm, Δ δ = ( − 37 ± 2 ) ppm, η C S = 0.78 ± 0.09 , with the quadrupolar coupling described by χ = ( 2.52 ± 0.01 ) MHz and η Q = 0.047 ± 0.003 . In contrast to the precisely determined tensor eigenvalues, the orientation of the eigenvectors in the crystal a b -plane of the vanadinite system could only be resolved by resorting to data obtained from density functional theory (DFT) calculations.

The chemical shift (CS) tensors for P-31 and Pb-207 in the natural mineral pyromorphite, Pb-5(PO4)(3)Cl, were determined from orientation-dependent NMR spectra of a single crystal, and MAS-NMR spectroscopic experiments. For the two crystallographically independent lead atoms in the hexagonal crystal lattice with space group P6(3)/m, the NMR parameters derived from the tensor eigenvalues are delta(iso) = -2172 ppm,eta(cs) = 0.08 for the Pb-207 at Wyckoff position 6h, and delta(iso) = -2810 ppm,eta(cs) = 0.49 for position 4f. For the P-31, which are also located at positions 6h, delta(iso) = -1.74 ppm and eta(cs) = 0.21 was found. A multi-parameter fit was utilized to extract the tensors from spectraacquired with one crystal rotation axis. The fit was sufficiently over-determined to also include the orientation of the crystal rotation axis into the fit, which could not be determined by X-ray diffraction because of the high absorption coefficient of pyromorphite, caused by the large lead content, and the large crystal size. In contrast to the precisely determined tensor eigenvalues, the orientation of the eigen-vectors in the crystal ab-plane of the pyromorphite system could only be resolved by using the results of density functional theory (DFT) calculations.

The full 207 Pb chemical shift (CS) tensor of lead in the mineral anglesite, PbSO 4 , was determined from orientation-dependent nuclear magnetic resonance (NMR) spectra of a large natural single crystal, using a global fit over two rotation patterns. The resulting tensor is characterised by the reduced anisotropy Δ δ = ( - 327 ± 4 ) ppm, asymmetry η C S = 0 . 529 ± 0 . 002 , and δ i s o = ( - 3615 ± 3 ) ppm, with the isotropic chemical shift δ i s o also verified by magic-angle spinning NMR on a polycrystalline sample. The initially unknown orientation of the mounted single crystal was included in the global data fit as well, thus obtaining it from NMR data only. By use of internal crystal symmetries, the amount of data acquisition and processing for determination of the CS tensor and crystal orientation was reduced. Furthermore, a linear correlation between the 207 Pb isotropic chemical shift and the shortest Pb–O distance in the co-ordination sphere of Pb 2 + solely surrounded by oxygen has been established for a large database of lead-bearing natural minerals.

A plasma-enhanced atomic layer deposition (ALD) process is presented, capable of producing thin conformal films of nickel(II) oxide (NiO) on various substrates. Nickelocene (NiCp2) is used as an inexpensive metal precursor with oxygen plasma as the oxidant. The film growth rate saturates with both nickel precursor and plasma exposure. An ALD window is observed between 225 and 275 degrees C. Linear growth is achieved at 250 degrees C with a growth rate of 0.042 nm per cycle. The thickness is highly uniform and the surface roughness is below 1 nm rms for 52 nm thick films on Si(100). Substrates with aspect ratios up to 1:10 can be processed. As-deposited, the films consist of polycrystalline, cubic NiO, and are transparent over the entire visible range with an optical bandgap of 3.7 eV. The films consist of stoichiometric NiO and contain approximate to 1% of carbon impurities. Two promising applications of these films are showcased in renewable energy conversion and storage devices: The films are pinhole-free and exhibit excellent electron blocking capabilities, making them potential hole-selective contact layers in solar cells. Also, high electrocatalytic activity of ultrathin NiO films is demonstrated for the alkaline oxygen evolution reaction, especially in electrolytes containing Fe3+.