Random-Walk Aggregation Phenomena in Solid Bimodal Liquid Dispersions: Transition to Nondeterminism from Si3N4to Si3N4+ Al2O3Aqueous Systems

This paper, which is based on another recent work, (Mezzasalma, S. A.,Phys. Rev. E55(4), (1997)) deals with experiments and theory concerning an aqueous dispersed system formed from silicon nitride (Si₃N₄), alumina (Al₂O₃), and mixed silicon nitride + alumina (Si₃N₄+ Al₂O₃) solid agglomerates. From titration data applied to a thermodynamic equilibrium condition, the minimum number of each agglomerate species and their maximal average dimensions have been derived as functions of the aqueous solution pH. These parameters are of the order of, respectively, (1–2) μm for Si₃N₄and Al₂O₃agglomerates and (20–50) μm for the mixed agglomerates. The numbers of solid particles of all species are poorly correlated with changes in pH of the liquid phase. This behavior has been interpreted as intrinsically related to the complexity of the system which, due to the many interactions among the different species, probably becomes nondeterministic. In order to describe such behavior a probabilistic approach has been developed. The probability of finding a given solid agglomerate number within a scatter band varies with the suspension pH. Furthermore, the scatter band amplitude becomes negligible near the isoelectric point. Accordingly, only the numbers of aggregates derived in the neighborhood of the isoelectric point are predictable.     

Synthesis of α-alumina from a less common raw material

A nanostructured α-Al₂O₃ with particle size lower than 100 nm was obtained from a hazardous waste generated in slag milling process by the aluminium industry. The route developed to synthesize alumina consisted of two steps: in the first one, a precursor of alumina, boehmite, γ-AlOOH was obtained by a sol–gel method. In the second step, the alumina was obtained by calcination of the precursor boehmite (xerogel). Calcination in air was performed at two different temperatures, i.e. 1,300 and 1,400 °C, to determine the influence of this parameter on the quality of resulting alumina. X-Ray diffraction patterns and transmission electron microscopy images of calcined powers revealed beside corundum the presence of transition aluminas and some rest of amorphous phase in the sample prepared at 1,300 °C. The increase of the calcinations temperature to 1,400 °C favors the formation of an almost single-phase corundum powder. The transition of θ- to α-Al₂O₃ was followed by means of infrared spectroscopy, since it is accompanied by the disappearance of the IR band frequencies associated with tetrahedral sites (AlO₄ sites), giving rise to a spectrum dominated by Al³⁺ ions in octahedral sites (AlO₆) characteristic of corundum.     

Isoconversional Kinetics of Thermal Processes in Mixtures Based on Metakaolin and Sodium Hydroxide

This study investigated the thermal behavior of the mixtures 6Al₂Si₂O₇: 12NaOH and 6Al₂Si₂O₇: 12NaOH: 2Al₂O₃ which are designed for synthesis of LTA (Linde type A) zeolite. XRD, SEM, and Synchronous thermal analysis (STA) have been used. It was found that after evaporating suspensions, molding pellets, and drying, small amounts of LTA and sodium hydroaluminates have been formed in the sample. The removal of crystallization water occurs on heating up to 400°C. In the temperature range from 400 to 850°C, Na₆Al₄Si₄O₁₇ and Na₈Al₄Si₄O₁₈ are synthesized by interaction of metakaolin with sodium hydroxide. The formation of mullite and nepheline is also observed. It was shown that preactivation of powders in the vibratory mill allows reducing the starting temperature of synthesis at 50–100°C. For the range 400–850°C using Ozawa–Flynn–Wall analysis, the values of apparent activation energy and preexponential factor have been calculated. It was established that the apparent activation energy for mixtures without preactivation made 200–290 kJ mol⁻¹. After preactivation, E values decreased to 130–170 kJ mol⁻¹. Also it was shown that alumina excess inhibits nepheline and mullite formation.     

A novel low temperature synthesis technique of sol–gel derived nanocrystalline alumina abrasive

The effect of ball milling process, co-doped seed and two step sintering technique on the properties of sol–gel derived alumina abrasive sintered at low temperature was investigated. The results showed that ball milling time with 10 h can be effective in enhancing the activity of the precursor and the microstructural uniformity of sintered alumina abrasive. A small amount of Al₂O₃–(NH₄)₃AlF₆ co-doped seed addition had potential synergistic effects for reducing α-Al₂O₃ phase transformation temperature and improving the mechanical property of alumina abrasive. A remarkable suppression of grain growth was achieved by controlling sintering temperature with two-step sintering method. Therefore, by using ball milling process, co-doping α-Al₂O₃–(NH₄)₃AlF₆ seed and two-step sintering technique, the sol–gel derived uniform nanocrystalline alumina abrasive is easily achieved at low temperature. Nanocrystalline alumina abrasive prepared at these conditions exhibited excellent mechanical properties and wear resistance compared to fused corundum abrasive and those sol–gel derived corundum abrasive with conventional sintering methods.     

Photoluminescence properties and application of yellow Ca0.65Si10Al2O0.7N15.3:xEu2+ phosphors for white LEDs

A series of yellow-emitting oxynitride Ca_0.65Si₁₀Al₂O_0.7N_15.3:xEu²⁺ phosphors with α-sialon structure were synthesized. The phase composition and crystal structure were identified by X-ray diffraction and the Rietveld refinement. The excitation and emission spectra, reflectance spectra and thermal stability were investigated in detail, respectively. Results show that Ca_0.65Si₁₀Al₂O_0.7N_15.3:0.12Eu²⁺ phosphors can be efficiently excited by UV-Vis light in the broad range of 290–450 nm and exhibit broad emission spectra peaking at 550–575 nm. The concentration quenching mechanism are discussed in detail and determined to be the dipole-dipole interaction. When the temperature increased to 150 °C, the emission intensity of Ca_0.65Si₁₀Al₂O_0.7N_15.3:0.12Eu²⁺ phosphor is 88.46% of the initial value at room temperature. White LED was fabricated with N-UV LED chip combined with blue Ca₃Si₂O₄N₂:Ce³⁺ and yellow Ca_0.65Si₁₀Al₂O_0.7N_15.3:Eu²⁺ phosphors. The color rendering index and correlated color temperature of this white LED were measured to 78.94 and 6728.12 K, respectively. All above results demonstrate that the as-prepared Ca_0.65Si₁₀Al₂O_0.7N_15.3:xEu²⁺ may serve as a potential yellow phosphor for N-UV w-LEDs.     

Sm2Si3O3N4 und Ln2Si2,5Al0,5O3,5N3,5 (Ln = Ce,Pr, Nd,Sm, Gd) – neuer synthetischer Zugang zu N‐haltigen Melilith‐Phasen und deren Einkristall‐Röntgenstrukturanalyse

Sm₂Si₃O₃N₄ and Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) – A Novel Synthetic Approach for the Preparation of N‐containing Melilites and X‐Ray Single‐Crystal Structure Determination The high‐temperature synthesis of nitridosilicates using an especially developed rf furnace was now transferred to the preparation of single‐crystalline oxonitridosilicates and oxonitridoaluminosilicates (sialons). Sm₂Si₃O₃N₄ was obtained by the reaction of SrCO₃, Si(NH)₂, and the respective lanthanoides, for Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) additionally AlN was used. The compounds were obtained as coarsely crystalline products. Their crystal structures were refined on the basis of single‐crystal X‐ray diffraction data. Sm₂Si₃O₃N₄ (a = 768.89(4), c = 499.60(4) pm) and the isotypic sialons Ce₂Si_2.5Al_0.5O_3.5N_3.5 (a = 779.20(3), c = 506.94(4) pm), Pr₂Si_2.5Al_0.5O_3.5N_3.5 (a = 778.26(4), c = 508.56(5) pm), Nd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 776.15(4), c = 506.7(3) pm), Sm₂Si_2.5Al_0.5O_3.5N_3.5 (a = 772.63(13), c = 502.80(9) pm), and Gd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 774.15(5), c = 506.46(4) pm) are new representatives of the N‐containing melilite structure type (space group P 4 2₁m (no. 113), Z = 2). For the structure analysis specific models were applied, which have been developed by Werner et al. on the basis of powder diffraction data.     

Neue Vertreter des Er6[Si11N20]O‐Strukturtyps Hochtemperatur‐Synthesen und Kristallstrukturen von Ln(6+x/3)[Si(11–y)AlyN(20+x–y)]O(1–x+y) mit Ln = Nd,Er, Yb,Dy und 0 ≤ x ≤ 3, 0 ≤ y ≤ 3

New Representatives of the Er₆[Si₁₁N₂₀]O Structure Type. High‐Temperature Synthesis and Single‐Crystal Structure Refinement of Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) with Ln = Nd, Er, Yb, Dy and 0 ≤ x ≤ 3, 0 ≤ y ≤ 3 According to the general formula Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) (0 ≤ x ≤ 3, 0 ≤ y ≤ 3) four nitridosilicates, namely Er₆[Si₁₁N₂₀]O, Yb_6.081[Si₁₁N_20.234]O_0.757, Dy_0.33Sm₆[Si₁₁N₂₀]N, and Nd₇[Si₈Al₃N₂₀]O were synthesized in a radiofrequency furnace at temperatures between 1300 and 1650 °C. The homeotypic crystal structures of all four compounds were determined by single‐crystal X‐ray diffraction. The nitridosilicates are trigonal with the following lattice constants: Er₆[Si₁₁N₂₀]O: a = 978.8(4) pm, c = 1058.8(3) pm; Yb_6.081[Si₁₁N_20.243]O_0.757: a = 974.9(1) pm, c = 1055.7(2) pm; Dy_0.33Sm₆[Si₁₁N₂₀]N: a = 989.8(1) pm, c = 1078.7(1) pm; Nd₇[Si₈Al₃N₂₀]O: a = 1004.25(9) pm, c = 1095.03(12) pm. The crystal structures were solved and refined in the space group P31c with Z = 2. The compounds contain three‐dimensional networks built up by corner sharing SiN₄ and AlN₄ tetrahedra, respectively. The Ln³⁺ and the “isolated” O^2– ions are situated in the voids of the structures. According to Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) an extension of the Er₆[Si₁₁N₂₀]O structure type has been found.     

Adsorption properties of hydrazine on pristine and Si-doped Al12N12 nano-cage

The interaction of hydrazine (N₂H₄) molecule with pristine and Si-doped aluminum nitride (Al₁₂N₁₂) nano-cage was investigated using the density functional theory calculations. The adsorption energy of N₂H₄ on pristine Al₁₂N₁₂ in different configurations was about –1.67 and –1.64 eV with slight changes in its electronic structure. The results showed that the pristine nano-cage can be used as a chemical adsorbent for toxic hydrazine in nature. Compared with very low sensitivity between N₂H₄ and Al₁₂N₁₂ nano-cage, N₂H₄ molecule exhibits high sensitivity toward Si-doped Al₁₂N₁₂ nano-cage so that the energy gap of the Si-doped Al₁₂N₁₂ nano-cage is changed by about 31.86% and 37.61% for different configurations in the Si_Al model and by about 26.10% in the Si_N model after the adsorption process. On the other hand, in comparison with the Si_Al model, the adsorption energy of N₂H₄ on the Si_N model is less than that on the Si_Al model to hinder the recovery of the nano-cage. As a result, the Si_N Al₁₂N₁₁ is anticipated to be a potential novel sensor for detecting the presence of N₂H₄ molecule.     

On the oxidation behaviour of monolithic TiB2 and Al2O3-TiB2 and Si3N4-TiB2 composites

In view of the susceptibility of TiB₂ to oxidation, the thermal stability of monolithic TiB₂ and of Al₂O₃-30 vol% TiB₂ and Si₃N₄-20 vol% TiB₂ composites was investigated. The temperature at which TiB₂ ceramic starts to oxidize is about 400°C, oxidation kinetics being controlled by diffusion up toT≈900°C and in the first stage of the oxidation at 1000°C and 1100°C (up to 800 min and 500 min respectively), and by a linear law at higher temperatures and for longer periods. Weight gains in the Al₂O₃-TiB₂ composite can be detected only at temperatures above ≈700°C and the rate governing step of the oxidation reaction is characterized by a one-dimensional diffusion mechanism atT=700°C andT=800°C and by two-dimensional diffusion at higher temperatures. Concerning the Si₃N₄-TiB₂ composite, three different oxidation behaviours related to the temperature were observed, i.e. up to ≈1000°C the reaction detected regards only the second phase; at ≈1000<T<≈1200°C, the diffusion of O₂ or N₂ through an oxide layer is proposed as the rate-governing step; atT〉=1200°C, a linear kinetic indicates the formation of a non protective scale.     

Interactions between the iron and the aluminum minerals during the heating of Venezuelan lateritic bauxites. II. X-ray diffraction study

Four samples of Venezuelan lateritic bauxites were heated to 300, 600 and 1000°C and the thermal reactions were studied by X-ray diffraction (XED) and by chemical extractability of silica and alumina. Gibbsite was converted to boehmite at 300°C, to an amorphous phase at 600°C and partly to corundum at 1000°C, with isomorphic substitution of Fe for some of the Al in the corundum structure. Goethite was converted to protohematite at 600°C and the hematite at 1000°C, with isomorphic substitution for Al for some of the Fe in both α-Fe₂O₃ varieties. Ti contributed by ilmenite is also occluded by the hematites. The occlusion of Ti takes place at 1000°C during the decomposition of the ilmenite and concomitant recrystallization of α-Fe₂O₃.     

Analytical scheme for tracing sources of contamination during processing of Si3N4 in clean rooms

This work investigates the uptake of impurities during processing of Si₃N₄ and describes an analytical scheme for detecting sources of contamination. For this purpose a process as simple and short as possible was chosen, using commercial starting materials with a high standard of purity and reproducibility. The uptake of non-metallic and metallic contaminants was investigated by choosing elements which were specific for individual processing steps. This was difficult in the determination of metallic impurities in a powder consisting of Si₃N₄ with Y₂O₃/Al₂O₃ additives, because the powder mixture and the sources of contamination (milling balls, attritor disk, wall materials) were similar in composition and the available analytical methods were not precise enough to detect the small increase in concentration that occurred. Therefore pure Si₃N₄ powders were milled in order to get an indication of the kind and concentration of impurity introduced by the individual milling materials and steps. These elements can then be used as monitor elements to trace sources of contamination and to optimize processing parameters. Experience with the processing of Si₃N₄ with Y₂O₃/Al₂O₃ additives by cyclic milling, spray drying, burn-out and isopressing are reported. Contamination by carbon is unavoidable. Its concentration during the process is relatively high, as it is added in the form of processing aids (deflocculants, binders), but temporary, as it can be completely burned out. Oxygen is predominantly taken up during milling. Good deflocculation reduces the milling time and thus limits the uptake of oxygen. As a consequence of these findings the processing parameters could be optimized. Thus the uptake of metallic impurities, e.g. Fe could be limited to 10 g/g and the uptake of oxygen was found to be less than 0.2 wt%.     

High-temperature synthesis and single-crystal X-ray structure determination of Sr10Sm6Si30Al6O7N54 — a layered sialon with an ordered distribution of Si,Al, O,and N

The novel oxonitridoaluminosilicate Sr₁₀Sm₆Si₃₀Al₆O₇N₅₄ has been obtained by the reaction of the powdered metals Sr and Sm with Si(NH)₂, SrCO₃ and AlN using a radiofrequency furnace at a maximum reaction temperature of 1600°C. The crystal structure of Sr₁₀Sm₆Si₃₀Al₆O₇N₅₄ has been determined by single-crystal X-ray crystallography (Fmm2, Z=4, a=1706.94(9), b=3332.4(2), c=995.36(5) pm, R₁=0.0706, wR₂=0.1273). This sialon represents a new structure type which has not been previously observed for a sialon. In the solid a capped double layer structure of the two-dimensional sialon network is formed by corner sharing SiON₃, SiN₄, AlON₃ and AlN₄ tetrahedra. A crystallographic differentiation of Si/Al and O/N seems reasonable on the basis of a careful evaluation of the single-crystal X-ray diffraction data combined with lattice energy calculations using the MAPLE concept.     

Structural studies of sialon ceramics by high-resolution solid-state NMR

High-resolution solide-state ²⁷Al NMR with magic-angle spinning (MASNMR) readily monitors the quantity and coordination (four- and six-fold) of aluminium in two ceramic materials of the SiAlON system. Sialon X-phase, of approximate composition Si₃Al₆O₁₂N₂, contains aluminium-centred octahedra and tetrahedra in the ratio ca. 1.9:1.0, while another sample containing a mixture of sialon polytypoids shows AlO₆ octahedra and a large quantity of what is most probably nitrogen-coordinated tetrahedral aluminium. In addition, ²⁹Si MASNMR detects two different kinds of silicon in the latter sample in a 2:1 ratio. These observations are interpreted satisfactorily in terms of the crystal structures of the compounds and provide further examples of the potential of MASNMR in the investigation of complex ceramic systems.     

Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si₃N₄ and Si₂N₂O are formed as the nitridation products in the samples. Fibroid and short columnar Si₃N₄ are detected in the samples. The formation mechanisms of Si₃N₄ and Si₂N₂O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O₂ in N₂ atmosphere, forming a thin film of SiO₂ on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO₂ film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO₂ film will crack, and N₂ is infiltrated into the central section of the sample through cracks, generating Si₂N₂O and short columnar Si₃N₄ in situ. At the same time, metastable SiO(g) reacts with N₂ and form fibroid Si₃N₄. In the regions where the oxygen partial pressure is high, Si₃N₄ is oxidized into Si₂N₂O.     

Synthesis of mesoporous alumina through photo cross-linked poly(dimethylacrylamide) hydrogels

Catalysis plays a central role in many fields of life, e.g., in biochemical processes, to reduce energy costs and resources in chemical industry and to decrease or even avoid environmental pollution and in energy management. Porous alumina (Al₂O₃) is an essential material in various applications, especially as a support material for catalysts. It is often prepared by nanocasting using porous carbon materials that serve as rigid structure matrices. In this work, an alternative way to synthesize mesoporous Al₂O₃ by using hydrogels as porogenic material is presented. Hydrogels can easily be patterned by light and used to imprint their structure onto alumina opening a new approach to fabricate patterned Al₂O₃. The hydrogels used in this work are based on poly(dimethylacrylamide) and were photo-chemically cross-linked. Followed by a nanocasting process, mesoporous alumina samples were synthesized and characterized by N₂ physisorption and X-ray diffraction. The cross-linker amount in the polymer network was varied and the influence on the properties of the Al₂O₃ is analyzed.     

Der Chromat‐Nosean Na8[Al6Si6O24](CrO4) — ein zeolithisches Gelbpigment?

A Chromate(VI) Oxide Ceramics Na₈[Al₆Si₆O₂₄](CrO₄) with Zeolitic Nosean Structure and Pigment Properties The cages of the zeolitic sodalite lattice can be occupied by half by the tetrahedral CrO₄^2— group, yielding a thermally stable, intense lemon‐yellow pigment, in which the colour centres are shielded completely from the atmosphere. The analyses yielded compositions Na₈[Al_6+2δSi_6—2δO₂₄](CrO₄)_1—δ with a small surplus of Al³⁺ and a CrO₄^2— deficiency (δ ≅ 0.15).     

Nd3Si5AlON10 – Synthese,Kristallstruktur und Eigenschaften eines Sialons im La3Si6N11‐Strukturtyp

Nd₃Si₅AlON₁₀ – Synthesis, Crystal Structure, and Properties of a Sialon Isotypic with La₃Si₆N₁₁ Nd₃Si₅AlON₁₀ was synthesized by the reaction of silicon diimide, aluminium nitride, aluminium oxide, and neodymium in a pure nitrogen atmosphere at 1650 °C using a radiofrequency furnace. The compound was obtained as a coarsely crystalline solid. According to the single‐crystal structure determination the title compound is isotypic with Ln₃Si₆N₁₁ (Ln = La, Ce, Pr, Nd, Sm). Nd₃Si₅AlON₁₀ (P4bm, a = 1007.8(1), c = 486.3(1) pm, Z = 2, R₁ = 0.016, wR₂ = 0.031) is built up by a three‐dimensional network structure of corner sharing SiON₃ and (Si/Al)N₄ tetrahedra (molar ratio Si : Al = 3 : 1). According to lattice energetic calculations using the MAPLE concept a differentiation of O and N seems to be reasonable. One of the two different sites for the tetrahedral centres is probably occupied by Si (distances: Si–O: 168.4(1), Si–N: 173.6(3)–176.0(4) pm) the second site by Si and Al with the molar ratio 3 : 1 (distances: (Si/Al)–N: 172.0(3)–176.6(2) pm). The Nd³⁺ ions are located in the voids of the (Si₅AlON₁₀)^9– framework (distances: Nd–O: 261.07(8), Nd–N: 246.1(2)–286.6(2) pm).     

Theoretical Investigation of the Solid State Reaction of Silicon Nitride and Silicon Dioxide forming Silicon Oxynitride (Si2N2O) under Pressure

The high‐pressure behavior of Si₂N₂O is studied for pressures up to 100 GPa using density functional theory calculations. The investigation of a manifold of hypothetical polymorphs leads us to propose two dense phases of Si₂N₂O, succeeding the orthorhombic ambient‐pressure polymorph at higher pressures:a defect spinel structure at moderate pressures and a corundum‐type structure at very high pressures. Taking into account the formation of silicon oxynitride from silicon dioxide and silicon nitride and its pressure dependence, we propose five pressure regions of interest for Si₂N₂O within the pseudo‐binary phase diagram SiO₂‐Si₃N₄: (i) stability of the orthorhombic ternary phase of Si₂N₂O up to 6 GPa, (ii) a phase assemblage of coesite, stishovite, and β‐Si₃N₄ between 6 and 11 GPa, (iii) a possible defect spinel modification of Si₂N₂O between 11 and 16 GPa, (iv) a phase assemblage of stishovite and γ‐Si₃N₄ above 40 GPa, and (v) a possible ternary Si₂N₂O phase with corundum‐type structure beyond 80 GPa. The existence of both ternary high‐pressure phases of Si₂N₂O, however, depends on the delicate influence of configurational entropy to the free energy of the solid state reaction.     

The preparation of fluoroarenes by the catalytic decarboxylation of aryl fluoroformates

The catalytic decarboxylation of phenyl fluoroformate to fluorobenzene has been achieved with yields of 70–80% in a flow system using alumina or alumina-based catalysts. The reaction occurs in short space times (<1 s) and with optimal efficiency at ca. 300 °C (some 500 °C lower than the temperature required for the thermal decomposition of the fluoroformate). Impregnation of the alumina with a platinum group metal gave the following order of catalytic activity; Pt/Al₂O₃>Pd/Al₂O₃>Rh/Al₂O₃≈Al₂O ₃.2,4,6-Trimethlyphenyl flouroformate, a new material, was found to decarboxylate similarly to give 1-flouro-2,4,6-trimethylbenzene, but 4-chlorophenyl flouroformate was noted to produce only low yields (～10%) of the corresponding arly flouride     

Synthesis and Luminescence Properties of Amber Emitting La7Sr[Si10N19O3] : Eu2+ and Syntheses of the Substitutional Variants RE8-xAEx[Si10N20-xO2+x] : Eu2+ with RE=La,Ce; AE=Ca,Sr, Ba; 0≤x≤2

The oxonitridosilicate La₇Sr[Si₁₀N₁₉O₃] : Eu²⁺ and its substitutional variants RE_8-xAE_x[Si₁₀N_20-xO_2+x] : Eu²⁺ with RE=La, Ce; AE=Ca, Sr, Ba and 0≤x≤2 were synthesized starting from REN, SrN/Ca₃N₂/Ba₂N, SiO₂, amorphous Si₃N₄ and Eu₂O₃ as doping agent at 1600 °C in a radiofrequency furnace. The crystal structure of La₇Sr[Si₁₀N₁₉O₃] was solved and refined based on single-crystal X-ray diffraction data. La₇Sr[Si₁₀N₁₉O₃] crystallizes in the orthorhombic space group Pmn2₁ (no. 31). The crystal structures of the isotypic compounds RE_8-xAE_x[Si₁₀N_20-xO_2+x] were confirmed by Rietveld refinements based on powder X-ray diffraction data using the single-crystal data of La₇Sr[Si₁₀N₁₉O₃] as starting point. Crystal structure elucidation reveals a 3D network of vertex sharing SiN₄ and SiN₂(N_1/2-x/4O_1/2+x/4)₂ (0≤x≤2) tetrahedra. When excited with UV to blue light, La₇Sr[Si₁₀N₁₉O₃] : Eu²⁺ shows amber luminescence with λ_em=612 nm and fwhm=84 nm/2194 cm⁻¹, which makes it interesting for application in amber phosphor-converted light emitting diodes.