N. Petrova

Yttrium-Zirconium Citric Complexes as Starting Material for Preparation of YSZ Powders and Layers

Yttrium−zirconium citric complexes prepared in ethylene glycol (EG) medium are used for preparation of yttria-stabilized zirconia (YSZ). The composition and some spectral characteristics of the complexes are studied and their formulae are derived. Most probably, they are of a mixed-metal nature. The utilization of the complexes for YSZ production allows the final product to be prepared at a rather low citric acid/ EG ratio. Thin films (200−1000 nm) of YSZ are deposited by spray pyrolysis using EG-solution of the complexes.

On the Chemistry of Pechini Process in Cerium Containing Systems

A short summary is made about some peculiarities in the composition, spectral characteristics and thermal decomposition of cerium citric and tartaric complexes, prepared at conditions analogous to that in the polymerized complex method. The nature of the bimetallic Ce(IV)-Ti(IV)and threemetallic Y-Fe-Ce-citrates is discussed. Special attention is paid on the changes in the Ce-oxidation state depending on the nature of the salt, used as Ce-source, the ligands and the temperature of synthesis.

Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO3 and La1−xCaxMnO3

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn3O4 (hausmannite) and LaMnO3 respectively. Parasitic phase(s) are observed in LaxCa1−xMnyO3, produced from LaCaMn-citrate.

Synthesis and characterization of Al-and Y-Al-citrates as potential precursors for YAlO3

Al-and Y-Al-citric complexes have been synthesized in ethylene glycol medium at conditions close to the ones used in polymerized complex method and their composition and spectral characteristics have been studied. Proofs have been found for the formation in the bimetallic system of a mixed-metal Al-Y-complex. Doubly ionized and esterified ligands take place in the Al-complex. All of the ligands forming Y-Al-complex are mono-or doubly esterified. Deprotonation of the alcoholic group takes place in the formation of the mixed-metal complex. Both complexes contain adduct-bonded ethylene glycol. Heating of the bimetallic complex or of the polyester resin formed leads to not phase-homogeneous YAlO3-along with cubic YAlO3, its orthorhombic modification as well as Y4All2O9 are found by X-ray diffractometry.

Combined laser and magnetic field treatment of YFeO3—containing films grown by spray-pyrolysis

Thin films (50–1200 nm) of YFeO3 were deposited on fused silica substrates by spray-pyrolysis using ethylene glycol solution of Y-Fe(III) citric complexes. The films were post deposition annealed at 750°C in static air for 2 h. Films obtained in this way were afterwards irradiated by a burst mode operated Nd-YAG laser (pulse energy 650 mJ, pulse duration 700 μs, energy density 110 mJ/cm2). The laser’s onset was synchronized with that of a magnetic field pulse of nearly square shape (magnetic induction 0.5 T, pulse duration 900 μs). The samples were placed normally to the direction of the magnetic field. The treatment does not affect the phase composition of the film but significantly increases the crystallite sizes of the phases presenting in the sample. The saturation magnetization of the films decreases as a result of the laser and magnetic field treatment and the coercive force increases by 50%.