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The synthesis of FeO3 and YFe1–xNixO3 (x = 0.1; 0.15; 0.2; 0.3; 0.5) nanocrystals was performed under the conditions of a self-propagating wave of glycine-nitrate combustion and their characterization and determination of the effect of Ni2+ doping of yttrium ferrite on the magnetic properties of nanopowders. The technology for the synthesis of yttrium orthoferrite nanoparticles (with and without doping with Ni2+ ions) by the glycine-nitrate combustion method at a ratio of G/N = 1 and 1.5 without adding a gelling agent to the reaction mixture and using ethylene glycol/glycerol is described. For the characterization of nanopowders based on YFeO3, the following were determined: phase composition and crystal structure (X-ray diffraction (XRD) method); size and structure of nanocrystal particles (transmission electron microscopy (TEM)); elemental composition of the samples (local X-ray spectral microanalysis (LXSMA)); magnetic characteristics (field dependences of specific magnetization). Thermal annealing of the synthesized samples at 800°C for 60 min led to the formation of the о-YFeO3 main phase. Undoped samples of yttrium orthoferrite were characterized by a particle diameter in the range of 5-185 nm, depending on the gelling agent used. YFe1-xNixO3 particles had a predominantly round shape with a size of 24 to 31 nm; the non-monotonic dependence of the average particle diameter on the dopant content was revealed: as the amount of dopant added increased, the average crystallite size tended to decrease. Nanopowders of undoped yttrium orthoferrite exhibit antiferromagnetic behaviour of magnetic susceptibility with temperature. The change in the magnetic properties of the nickel-doped YFeO3 nanocrystalline powders was due to the incorporation of Ni2+ into the Fe3+position, which led to the formation of a material with more pronounced soft magnetic properties at a substitution degree of 0.1. Samples with high degrees of substitution (x = 0.15 and 0.3) were also characterized by paramagnetic behaviour at temperatures above 100 K.

In this work, we aimed to prepare chromium substituted cobalt ferrite Co(CrxFe1–x)2O4 powders by a simple coprecipitationannealing method with different Cr contents to create novel magnetic adsorbents for the removal of phosphate ions from water. The effects of Cr substitution on the crystal structure, phase composition, morphology, surface atomic composition, surface area and magnetic properties of our adsorbents were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller nitrogen adsorption-desorption and vibrating sample magnetometry. According to the results, all our Co(CrxFe1–x)2O4 samples exhibited higher phosphate adsorption than CoFe2O4 powder but their magnetic properties were reduced for increasing Cr substitution. Among them, the Co(Cr0.25Fe0.75)2O4 sample was found to be the most promising material since its magnetic properties are still high to allow it to be easily separated from the solution and its maximum P adsorption capacity (according to the Langmuir model) was estimated to be 4.84 times higher than CoFe2O4, which can be attributed to the presence of Cr3+ ions on the surface and the enhanced surface specific area of this substituted sample. Moreover, the adsorption data of Co(Cr0.25Fe0.75)2O4 sample also fitted well to the pseudo second order kinetic model, revealing the adsorption rate constant of 0.87 mgP–1s–1, two times superior to CoFe2O4.

Nanocrystalline copper (II) ferrite with a spinel structure doped with holmium was synthesized by co-precipitation using an aqueous solution of NaOH as a precipitant and subsequent annealing at 800°C for 60 min. The doping limit was determined by X-ray phase analysis. The similarity of the real and nominal compositions of the doped samples was established by energy-dispersive X-ray spectroscopy using a scanning electron microscope. The obtained particles had an approximately spherical shape, and their size was 40–70 nm (X-ray phase analysis, transmission electron microscopy). The introduction of Ho3+ cations to х = 0.15 into a CuFe2O4 spinel lattice led to a decrease in the average size of crystallites, an increase in the coercive force of nanopowders, and a decrease in excess magnetization and saturation magnetization. Synthesized CuFe2-xHoxO4 (х = 0, 0.1 and 0.15) nanopowders were magnetically hard materials with high coercive force.

In this work, orthoferrite NdFeO3 nanomaterials with particle sizes 20-40 nm have been successfully synthesized via a simple co-precipitation method through the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. Single-phase NdFeO3 was generated after calcination of the as-prepared powder at 700, 800, and 900 °C for 1 hour. The UV-Vis spectra at room temperature presented strong absorption in the UV-Vis regions (l = 200–400 nm and 400–600 nm) with small band gap energy (Eg = 2.2÷2.5 eV). The obtained NdFeO3 nanomaterials exhibited a hard ferromagnetic behavior with high coercivity (Hc = 600–1600 Oe).

In this work, nano-sized crystalline praseodymium orthoferrite was successfully synthesized via sol-gel method using water – methanol co-solvent. Single-phase PrFeO3 nanoparticles were formed after annealing the precursors at 650, 750, 850, and 950 °C during 60 min. The crystal size, lattice volume and coercivity (Hc) of nanocrystalline PrFeO3 increase with the annealing temperature. The obtained praseodymium orthoferrite exhibited paramagnetic properties with Hc = 28 – 34 Oe

Iris family in the countries of eastern part of Indochina Peninsula, such as Cambodia, Laos and Viet­nam includes lone native genus – Iris L. with two aboriginal species – I. japonica Thunb. and I. tectorum Maxim. Iris japonica is often cultivated as an outdoor ornamental plant in mountainous regions in the northern Vietnam, where it occasionally naturalizes. Herbarium specimens of I. japonica, collected in central Laos near Nape town, probably represent southernmost locality of the Iris genus in Eurasia. Iris tectorum was discovered in native, primary plant communities of karstic highly eroded limestone in Cao Bang province (Bao Lac district) of the northern Vietnam. This species is recorded as new for the flora of the Indochina Peninsula. The report of I. collettii Hook. f. on the territory of peninsular flora does not yet confirmed by herbaria and remains doubtful. Data on taxonomy, authentic specimens, distribution, habitats, phenology, conservation status and biology are provided for all Iris species. The identification key for Iris species is compiled, as well as dotted distribution maps on the territory of countries of eastern Indochina. Other representatives of the family from such genera as Belamcanda Adans. (B. chinensis (L.) Redouté), Crocosmia Planch. (C. × crocosmiiflora (G. Nicholson) N. E. Br.), Eleutherine Herb. (E. bulbosa (Mill.) Urb.), Freesia Klatt (F. refracta (Jacq.) Klatt.), Gladiolus L. (numerous horticultural forms) и Trimezia Salisb. ex Herb. (T. martinicensis (Jacq.) Herb.) reported from Indochina are introduced cultivated ornamental plants capable to occasional naturaliza­tion as an adventive element of the Indochinese flora.