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Co-crystallization of cyclic nitramines with sterically crowded molecules, i.e., ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-CL-20) with cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), is very difficult, but the co-agglomeration (slurry method) of their mixed micro-co-particles gives very good results. CL-20 is present in these co-agglomerates (CACs) in its β-form. Besides the medium of co-agglomeration, also the molar ratio is very important; it is possible to obtain β-CL-20/BCHMX (molar 1.8/1.0) with the impact sensitivity of 14.9 J. The density of these CACs approaches 99.6% of the density of the β-CL-20 crystals. Based on the application of the Raman, FTIR and PXRD techniques, it has been proved that the agglomeration of CL-20/BCHMX micro-co-particles leads to the formation of CACs mostly with the properties of co-crystals (CCs). This also seems to be confirmed by the relationships between the heat of formation and ring-deformation vibrations (in plane) and between the impact sensitivity and the difference in the asymmetric NO2 stretching vibrations in pure CL-20 and its CACs. The CACs studied have lower detonation energies than would be consistent with the percentage of individual coformers in these crystals. An examination of the most sensitive CACs (1.2 J) as a detonator primer has shown the absence of its required acceleration capabilities in the given detonator design. A comparison with literature data and our unpublished preliminary results indicates that the CACs and CCs of this type could have potential beneficial applications in propellants. [ABSTRACT FROM AUTHOR]

The mixed oxide LaNiO3 with perovskite structure was prepared by two relatively new and unconventional methods including preparation and thermal decomposition of mixed metal oxalate or carbonate precursors. The intermediates were prepared by reaction in a highly concentrated suspension (paste). The thermal decomposition conditions of these intermediates were described, and the final calcination temperatures were determined, which were done using thermal analysis methods and X-ray diffraction. During the decomposition of mixed carbonates, one-phase LaNiO3 is produced directly, and in case of decomposition of oxalates, a mixture of LaNiO3 and La2O3 is produced due to the formation of La2O2CO3 during the heating. Catalytic decomposition of nitrous oxide at high temperature (650–930 °C) and high loading (GHSV = 350,000 h−1) has shown high LaNiO3 activity, even at lower temperatures. The results were compared with the same compound obtained by co-precipitation and by solid-state reaction. Methods of preparation based on decomposition of oxalate and carbonate intermediates lead to the preparation of materials with appropriate composition, morphology, specific surface and high catalytic activity. [ABSTRACT FROM AUTHOR]

Perovskite pigments with SrCrxSn1−xO3−δ (x = 0.025, 0.05, 0.1, 0.2, 0.3) composition were prepared by a solid-state reaction, suspension mixing of materials and mechanochemical activation of initial reagents with calcination at high temperature. Results of thermal analysis show the effectivity of mechanochemical activation of reaction mixture that shifts the reaction course to lower temperature. Solid solution of SrSn0.975Cr0.025O3−δ was prepared at temperature 1200 °C. The optimal composition for synthesis of the intense red–pink powder is SrSn0.975Cr0.025O3−δ (L*/a*/b* = 36.34/14.21./1.12). Red–pink colour of the pigments is explained in terms of crystal field theory. The partial substitution of tin ions by chromium ions leads to the formation of the optical absorption bands corresponding to the O2p–Cr3d charge transfer transitions. Pigment is distinguished by good chemical stability in a molten ceramic glaze and high value of solar reflectance in the near-infrared region of light (R* ≈ 61%). [ABSTRACT FROM AUTHOR]

Light brown inorganic pigments based on BiFeO3 doped by Sr2+ cations were prepared by a conventional solid-state reaction at high temperature. This study is focused on the synthesis of Bi1−xSrxFeO3−δ powders in a range of substitution (x = 0-0.35; with step size 0.05). The main role of strontium is to overcome the defects that come to exist during the evaporation of Bi over material preparation. The substitution of trivalent bismuth ions by divalent strontium ions results in oxygen deficiency in the lattice, which was proved by both thermogravimetric analysis and elemental analysis. The substitution has a positive effect on the thermal stability of samples. The thermal stability of BiFeO3 is 1046 K, whereas the substitution of 20 mol% of Bi3+ by Sr2+ ions shifted it to 1403 K and powder with composition Bi0.65Sr0.35FeO3−δ has a thermal stability that is higher than 1434 K. An increasing range of substitution is connected with the change in the pigment color from reddish-brown to orange-brown and back to reddish-brown. The Bi0.85Sr0.15FeO3−δ pigment prepared by calcination at 1273 K offers the most interesting color properties (L* = 45.57; a* = 20.38; b* = 26.23). [ABSTRACT FROM AUTHOR]

All the known chromium(III) NASICON-related phosphates are considered to be solid solutions. In these compounds chromium atoms share their position in the basic framework of the crystal lattice with other structure forming elements such as zirconium. In our study, we have hypothesised a completely new way of structural organisation of the chromium(III) zirconium(IV) NASICON framework, consisting in the distribution of chromium over the charge-compensating atom sites with tetrahedral oxygen coordination. The possibility of formation of the corresponding phosphate, Cr1/3Zr2P3O12, was studied using a classical ceramic route and a sol-gel method. Structural affiliation of the obtained pure phase product was studied using XRD analysis. The results confirmed that the Cr1/3Zr2P3O12 phosphate belongs to monoclinic SW-subtype of the NASICON family. In this structure, chromium atoms occupy charge-compensating sites with a strongly distorted tetrahedral oxygen environment. To the best of our knowledge, it is the first example of tetrahedral coordination of chromium(III) in phosphates. Along with the unusual crystallographic characteristics of chromium, special attention in this paper is devoted to the thermal stability of this phosphate and to its performance as an inorganic pigment. The sample was characterised by heating microscopy and DTA study, particle size distribution analysis, and IR- and VIS-spectroscopy. The stability of the obtained powder in a glaze environment, its colouring performance and lightfastness are discussed as well. [ABSTRACT FROM AUTHOR]

Light brown inorganic pigments based on BiFeO3 doped by Sr2+ cations were prepared by a conventional solid-state reaction at high temperature. This study is focused on the synthesis of Bi1−xSrxFeO3−δ powders in a range of substitution (x = 0-0.35; with step size 0.05). The main role of strontium is to overcome the defects that come to exist during the evaporation of Bi over material preparation. The substitution of trivalent bismuth ions by divalent strontium ions results in oxygen deficiency in the lattice, which was proved by both thermogravimetric analysis and elemental analysis. The substitution has a positive effect on the thermal stability of samples. The thermal stability of BiFeO3 is 1046 K, whereas the substitution of 20 mol% of Bi3+ by Sr2+ ions shifted it to 1403 K and powder with composition Bi0.65Sr0.35FeO3−δ has a thermal stability that is higher than 1434 K. An increasing range of substitution is connected with the change in the pigment color from reddish-brown to orange-brown and back to reddish-brown. The Bi0.85Sr0.15FeO3−δ pigment prepared by calcination at 1273 K offers the most interesting color properties (L* = 45.57; a* = 20.38; b* = 26.23). [ABSTRACT FROM AUTHOR]

Due to the outstanding stability and resistivity to dissolution agents of the compounds related to NaZr2(PO4)3 (NZP family), our attention has been focussed on CoZr4(PO4)6 and its performance as an inorganic pigment for coloration of ceramic glazes. Mixed cobalt zirconium phosphate has been prepared by a solid state reaction and a sol–gel method and was characterised (through thermal analysis, XRD, heating microscopy, SEM, VIS-spectrophotometry and lightfastness measurement) for the first time as a ceramic pigment. In order to reduce the cobalt content in the samples the series of Co1−x Mg x Zr4(PO4)6 (x = 0.25; 0.5) have also been prepared using a solid state reaction and were investigated with the same techniques. It was shown that a solid state reaction provides the formation of CoZr4(PO4)6 through a three component system stage (ZrP2O7, ZrO2 and CoP2O6/Co2P2O7), when employment of the sol–gel method leads to the direct formation of a CoZr4(PO4)6 phase at lower temperatures. During further thermal treatment, with an increase of the calcination temperature up to 1200–1300 °C, an additional phase of Zr2O(PO4)2 appears in the composition. A solid state reaction can be suggested as a preferable method for achieving enhanced thermal stability of this phosphate and the substitution of Co by Mg not only helps to reduce the content of Co in the sample compositions, but also to improve their thermal characteristics. Thus, the obtained results indicate that employment of the more complicated sol–gel method does not provide any advantages at high calcination temperatures with respect to the phase composition, thermal stability, homogeneity and particle size distribution of the obtained samples and the conventional ceramic route does not deteriorate on the basis of these parameters. An irregular change of the colour parameters was observed for the samples during the calcination and the temperature of 1300 °C and 6–12 h of soaking time were chosen for pigment synthesis. Colouring ability of the obtained samples has been analysed with two types of ceramic glazes. The mixed phosphates exhibit saturated purple-blue colour, which becomes lighter only with an increase of Mg content to x = 0.5. Enamelled samples showed excellent lightfastness and the investigated compounds can be considered as high performance inorganic pigments for coloration of ceramic glazes. [ABSTRACT FROM AUTHOR]

All the known chromium(III) NASICON-related phosphates are considered to be solid solutions. In these compounds chromium atoms share their position in the basic framework of the crystal lattice with other structure forming elements such as zirconium. In our study, we have hypothesised a completely new way of structural organisation of the chromium(III) zirconium(IV) NASICON framework, consisting in the distribution of chromium over the charge-compensating atom sites with tetrahedral oxygen coordination. The possibility of formation of the corresponding phosphate, Cr(1/3)Zr2P3O12, was studied using a classical ceramic route and a sol-gel method. Structural affiliation of the obtained pure phase product was studied using XRD analysis. The results confirmed that the Cr(1/3)Zr2P3O12 phosphate belongs to monoclinic SW-subtype of the NASICON family. In this structure, chromium atoms occupy charge-compensating sites with a strongly distorted tetrahedral oxygen environment. To the best of our knowledge, it is the first example of tetrahedral coordination of chromium(III) in phosphates. Along with the unusual crystallographic characteristics of chromium, special attention in this paper is devoted to the thermal stability of this phosphate and to its performance as an inorganic pigment. The sample was characterised by heating microscopy and DTA study, particle size distribution analysis, and IR- and VIS-spectroscopy. The stability of the obtained powder in a glaze environment, its colouring performance and lightfastness are discussed as well.