M. Kurzawa

Reinvestigation of Phase Equilibria in the V2O5–ZnO System

A diagram of phase equilibria established in a two-component oxide system V25–ZnO has been worked out applying differential thermal analysis and X-ray phase analysis as well as depending on investigations carried out with the aid of high-temperature X-ray attachment and scanning electron microscope linked to an X-ray microanalyser.

Reactivity of FeVO4 towards oxides and pyrovanadates(V) of Co and Ni

Abstract A novel Co 2 FeV 3 O 11 compound was obtained from a solid state reaction. Co 2 FeV 3 O 11 undergoes a reversible polymorph transition at 770 ± 5°C. It melts congruently at 980 ± 5°C. The indexing results and the calculated unit cell parameters for both polymorphs of Co 2 FeV 3 O 11 as well as for the previously obtained Ni 2 FeV 3 O 11 and Ni 2 FeVO 6 compounds are given. The IR spectra of the above-mentioned compounds are presented.

The synthesis and selected properties of new compounds: Mg3Fe4(VO4)6 and Zn3Fe4(VO4)6

Abstract New compounds: Mg3Fe4(VO4)6 and Zn3Fe4(VO4)6 were obtained from a solid state reaction. The temperatures of melting of Mg3Fe4(VO4)6 and Zn3Fe4(VO4)6 amount to 950±5 and 850±5°C, respectively. The indexing results and the calculated unit cell parameters for both compounds are given and suggest that both phases are isotypic with Mn3Fe4(VO4)6. The IR spectra of the above-mentioned compounds are presented.

The FeVO4-MoO3 system

A phase diagram of the FeVO4-MoO3 system has been constructed from the results of DTA and X-ray analysis. The components of the system form a compound FeVMoO7. This compound melts incongruently at 680±5 °C, with separation of the solid Fe4V2Mo3O20.ZusammenfassungDas Phasendiagramm des Systems FeVO4-MoO3 wurde basierend auf Ergebnissen der DTA und Röntgenanalyse aufgestellt. Die Komponenten des Systems bilden die Verbindung FeVMoO7,. Diese Verbindung schmilzt inkongruent bei 680±5° unter Abscheidung von festem Fe4V2Mo3O20.РезюмеФазовая диаIрамма сис темы FeVO4-МоО3 была установлена на основ е измерений ДТА и фазивого анализ а. Компоненты системы образуют соединение FeVMoO7, которое плавилось инконгруэ нтно при 680 ±5 °? с выделен ием твердого вещества Fe4V2Mo3O20.

Neutron diffraction study of Mg2FeV3O11-δ

The neutron diffraction patterns of Mg2FeV3O11-δ compound at various low temperatures have been investigated. No magnetic ordering was observed in the investigated temperature range down to 10K. These materials have been formed in the triclinic space group but there are specific differences in the positions of atoms as compared to previously determined from XRD method. The iron(III) ions are distributed non-statistically with magnesium(II) ions and this could be responsible for some differences in the structure of the above sample. The method of sample preparation, in particularly thermal annealing processes could be responsible for the differences.

Study of the solid solution of MoO3 in Fe2V4O13

Differential thermal and phase X-ray analyses have shown that MoO3 and Fe2V4O13 form a solid substitution solution, in which Mo6+ ions are incorporate into the crystal lattice of Fe2V4O13 in place of V5+ ions. The solubility limit of MoO3 in Fe2V4O13 at ambient temperature is 18 mole % of MoO3. The phase equilibria in the system Fe2V4O13-FeVMoO7, were also studied. Results are presented in the form of a phase diagram.ZusammenfassungDurch DTA und Röntgenphasenanalyse wurde gezeigt, daß MoO3 und Fe2V4O13 Substitutionsmischkristalle bilden, in denen Mo6+-Ionen anstelle von V5+-Ionen in das Kristallgitter von Fe2V4O13 eingebaut sind. Die Löslichkeitsgrenze von MoO3 in Fe2V4O13 beträgt bei Umgebungstemperatur 18 Mol-% MoO3. Ebenfalls wurden die Phasengleichgewichte im System Fe2V4O13-FeVMoO7 untersucht. Die Ergebnisse sind in Form eines Phasendiagramms dargestellt.РезюмеДифференциальный те рмический и рентгено-фазовый ана лизы показали, что МоО3 и Fe2V4O13 образуют твердый р аствор замещения, в ко тором ионы Мo6+ замешают ионы V5− в кристаллической реш етке Fe2V4O13. Предел растворимости МоО3 в Fe2V4O13 при обычной температуре составл яет 18 мольных %. Изучено также фазовое равновесие с истемы Fe2V4O13-FeVMoO7 и результаты предста влены в форме фазовой диаграммы.

Studies on chromium(III) molybdate and equilibria in the CrVO4-Cr2(MoO4)3 system

Abstract The behaviour of Cr 2 (MoO 4 ) 3 towards CrVO 4 up to 1000 °C over the entire range of component concentrations was investigated using differential thermal analysis and X-ray powder diffraction. The results are shown in the form of a phase diagram. Chromium(III) molybdate decomposes to Cr 2 O 3 and MoO 3 before reaching its melting point. The decomposition of Cr 2 (MoO 4 )3 takes place at 810°C accompanied by the sublimation of MoO 3 .

Diffuse reflectance spectra of iron(III) vanadates

Abstract The electronic spectra of solid iron(III) vanadates FeVO 4 and Fe 2 V 4 O 13 were investigated by the diffuse reflectance technique in the spectral range 12 500–50 000 cm −1 . The spectra of investigated vanadates contain 2–3 intensive CT bands in the UV region and two lowest energy d – d bands in the 12 000–22 000 cm −1 range. The presence of the weak bands for FeVO 4 and Fe 2 V 4 O 13 at 16 500 cm −1 and 20 500 cm −1 points to the lattice deffects (oxygen deficiency and the presence of the V 4+ ions) in the structure of investigated vanadates.

Phase equilibria in the FeVO4-Fe2(MoO4)3 system

Phase équilibria have been investigated in the FeVO4-Fe2(MoO4)3 system for the whole concentration range of the components. In this system there is one compound which melts incongruently: Fe4V2Mo3O20. The results are presented in the form of a phase diagram.ZusammenfassungPhasengleichgewichte im System FeVO4-Fe2(MoO4)3 wurden über den ganzen Konzentrationsbereich der Komponenten hinweg untersucht. Eine Verbindung des Systems, Fe4V2Mo3O20, schmilzt inkongruent. Die Ergebnisse sind in Form eines Phasendiagramms angegeben.РЕжУМЕИсслЕДОВАНО ФАжОВОЕ РАВНОВЕсИЕ сИстЕМы FeVO4-Fe2(MoO4)3 ВО ВсЕИ ОБлАстИ кОНцЕНтРАцИИ кОМпОН ЕНтОВ. В ИжУЧЕННОИ сИс тЕМЕ НАИДЕНО сОЕДИНЕНИЕ Fe4V2Mo3O20, плАВьЩЕЕсь ИНкОНгРУ ЕНтНО. пОлУЧЕННыЕ РЕж УльтАты пРЕДстАВлЕНы В ФОРМЕ ФАжОВОИ ДИАгРАММы.

PHASE EQUILIBRIA IN THE SYSTEM NiO-V2O5-Fe2O3 IN SUBSOLIDUS AREA

Reactivity of FeVO4 towards Ni2V2O7 and Ni3V2O8 in the solid state was investigated. On the base of XRD and DTA results, phase diagrams in subsolidus area of the FeVO4-Ni2V2O7 and FeVO4-Ni3V2O8 intersections of the ternary system NiO-V2O5-Fe2O3 have been worked out and the phase diagram of this ternary system in subsolidus area in the whole component concentration range has been verified.