Nb Ratio Research Articles

Mineral chemistry of tantalate species new in the Borborema Pegmatitic Province, Northeast Brazil

Tantalate samples, supposedly of the columbite group, were collected in the Borborema Pegmatitic Province, aiming to test the Mn/(Mn+Fe) and Ta/(Ta+Nb) ratios as geochemical indicators of pegmatite fractionation. Surprisingly, preliminary microprobe data allowed recognizing some species, so far unknown in the Province, namely titanian ixiolite, fersmite, brannerite, strüverite, natrobistantite, plumbo- and stibiomicrolite, plumboand uranpyrochlore. The identification of these exotic tantalates with unusual composition, in addition to its distribution in several pegmatites, far from the classical Alto do Giz and Seridozinho pegmatites, indicate that the elevated degree of fractionation is not restricted to these two occurrences but may be reached in other pegmatite areas of the Province. It indicates also that this degree of fractionation may be very variable between pegmatites in small areas. The zoning patterns observed in the titanian ixiolite, with Ti and Nb enrichment at the borders at expense of Ta enriched in the core, are also quite unusual and reverse in comparison with the normal trend of progressive Ta and Mn enrichment in tantalates with the degree of fractionation. A similar "reverse" trend was observed in titanian wodginite of petalite/pollucite bearing pegmatites of the Separation Rapids Province in Ontario, Canada.

Determination of the Ta and Nb ratio in LiNb 1− xTa xO 3 by total reflection X-ray fluorescence spectrometry

A procedure for evaluation of the mass ratio between Ta and Nb in LiNb 1− x Ta x O 3 single crystals by total reflection X-ray fluorescence spectrometry (TXRF) is described. The developed procedure does not require chemical preparation of the samples and it proves to be fast (30 min for sample preparation and 10 min for analysis), precise (down 1% RSD) and easy to perform. To check the methodology, the lattice parameter of each LiNb 1− x Ta x O 3 sample was determined by powder X-ray diffraction. While the a hexagonal lattice parameter remains constant, a strong and linear dependence of the c hexagonal lattice parameter with Ta content in molar percentage has been observed for the first time.

Stoichiometry and doping mechanism of the cubic pyrochlore phase in the system Bi2O3–ZnO–Nb2O5

The subsolidus phase diagram of the system Bi2O3–ZnO–Nb2O5 in the region of the cubic pyrochlore phase has been determined at 950 °C. This phase forms a solid solution area that does not include the so-called ideal composition P, Bi3Zn2Nb3O14. It may be described in terms of two compositional variables: ZnO deficiency compared to P together with variable Bi : Nb ratio. Density measurements, preliminary crystallographic studies and the phase diagram indicate the solid solutions to have general formula, Bi3+yZn2−xNb3−yO14−x−y: −0.11(1) ≤ y ≤ 0.14(1) and −0.03(1) ≤ x ≤ 0.31(1).

Paleoproterozoic arc and ophiolitic rocks on the northwest-margin of the Trans-Hudson Orogen, Saskatchewan, Canada: their contribution to a revised tectonic framework for the orogen

A new lithotectonic framework for the northwestern Reindeer Zone of the Trans-Hudson Orogen divides rocks into five northwest- to north-dipping volcano-sedimentary assemblages: (1) at the structural base, the 1.92–1.87 Ga largely sedimentary Levesque Bay Assemblage (partly equivalent to former ‘MacLean Lake gneisses’), which lies within the confines of the Kisseynew Domain and is tectonically imbricated with metasedimentary rocks of the <1.85 Ga McLennan and Burntwood groups; (2) the turbiditic Duck Lake Assemblage, also located along the northern edge of the Kisseynew Domain; it contains detrital zircons ranging in age between 1.92 and 1.87 Ga; (3) the ?1.92 Ga mafic–ultramafic volcano-plutonic Lawrence Point Assemblage of the La Ronge Domain; (4) the ≥1.88 Ga felsic to intermediate volcano-plutonic Reed Lake Assemblage of the La Ronge Domain; and (5) the turbiditic Milton Island Assemblage of the Rottenstone Domain, which contains detrital zircons ranging in age between 2.83 and 1.86 Ga. The assemblages are intruded by a variety of 1.91–1.78 Ga mafic to felsic plutons. The Lawrence Point Assemblage is interpreted as a dismembered supra-subduction zone ophiolite. High-MgO refractory harzburgite (‘Group 1’ ultramafic rocks), at the structural base of the assemblage, is geochemically identical to the upper mantle section of selected supra-subduction zone ophiolites and mantle tectonites. Chromite and olivine compositions of the ‘Group 1’ ultramafic rocks are also comparable to those of ophiolitic harzburgite and mantle tectonite. Mafic metavolcanic rocks of the assemblage are classified as subalkaline tholeiitic basalts. Their trace element patterns and Hf, Ta, Th, Y, Nb, and La element ratios resemble those of modern back-arc basin basalts. The Reed Lake Assemblage represents a subduction-generated arc complex that was built on top of the Lawrence Point Assemblage; its mafic metavolcanic rocks are subalkaline basalts, with calc-alkaline trends, and elevated Th and Ce concentrations and negative Nb anomalies. Feldspar porphyry dykes intruding the Lawrence Point and Duck Lake assemblages constrain timing of Lawrence Point ophiolite emplacement onto the Duck Lake Assemblage to 1.86–1.84 Ga. The trace element geochemistry of the dykes suggests continued arc volcanism after ophiolite emplacement. Mafic metavolcanic rocks of the Levesque Bay Assemblage are geochemically similar to those of the Lawrence Point Assemblage. Other ultramafic rocks (peridotite to pyroxenite) are abundant in the Lawrence Point Assemblage, but have similar geochemistry to small ultramafic bodies intruding the Reed Lake, Duck Lake and Levesque Bay Assemblages. They represent a separate, later phase (?1.86 Ga) of ultramafic plutonism, which post-dates ophiolite emplacement. Timing of Lawrence Point ophiolite emplacement (between 1.86 and 1.84 Ga) and geochemistry of later felsic and mafic/ultramafic volcanism suggest that the Lawrence Point ophiolite and overlying Reed Lake arc assemblage were not accreted to the Hearne Craton prior to 1.86 Ga, but were first accreted to the Flin Flon–Glennie Complex after 1.86 Ga.

Growth and two-color holographic storage properties of Mn-doped lithium niobate crystals with varying Li∕Nb ratio

Near-stoichiometric LiNbO3 crystals slightly doped with Mn from melts with different compositions are grown by the top seeded solution growth method. The growth parameters such as temperature field, pulling, and rotation rates are optimized. Two-color holograms are recorded in these crystals by the use of a near infrared laser of 778 nm for writing and an ultraviolet laser of 350 nm for gating. The light-induced absorption changes and two-color holographic characteristic performances are presented and compared. The results show that crystals with composition closer to stoichiometry exhibit better two-color holographic storage performance.

Dielectric investigation of a new TKWB lead free relaxor

A new lead-free tungsten bronze (TKWB) type relaxor derived from Ba 1− x Sr x Nb 2O 6 and containing Sn was prepared via classical solid state route. A 2.5% Sn:Nb ratio was enough to both induce the relaxor effect and bring the transition temperature close to room temperature. Promising dielectric characteristics were evidenced, in particular when compared to perovskite-type lead-free relaxors. Chemical bonding arguments are used to explain the role of tin in the structure-dielectric properties relationships.

On the origin of EM-I end-member

On the basis of geochemical data available for oceanic basalts distinct mantle reservoirs have been identified during the last decades. Among these reservoirs, the EM-I end-member (Enriched Mantle type I) shows almost unique geochemical characteristics. The definition of the EM-I end member and the petrogenetic processes related to its origin are still debated: the geochemical composition of EM-I basalts has been interpreted in terms of crust-mantle interaction during 1) mantle recycling of subducted crustal material; 2) detachment of lithospheric keels in over-thickened regions; 3) thermal erosion by anomalously hot mantle. Key features of the EM-I end-member are: low uranogenic Pb ratios ( 2 0 6 Pb/ 2 0 4 Pb 0.85), and 2 0 8 Pb/ 2 0 6 Pb (>2.08). EM-I basalts show apparent or inexistent Ba, Pb, Eu or Sr anomalies in primitive mantle-normalized diagrams and have Ba/ Nb ratios ranging from 3.5 to 47.4, Ce/Pb from 1.2 to 24.6, Nb/U from 10.5 to 71.8, Sr/ Nd from 6.2 to 36.4, and Eu/Eu* from 0.83 to 1.25. On these basis, the origin and evolution of the EM-I end-member cannot be explained by a single petrological model, and even the definition of elemental and isotopic parameters is controversial.

Determination of the Li/Nb ratio in LiNbO3 crystals prepared by vapor transport equilibration method

Off-congruent lithium niobate (LiNbO 3 ) single crystal was prepared by vapor transport equilibration (VTE). The Li/ Nb ratio was determined by means of indirect methods such as the lattice parameters, the fundamental absorption edge position and the IR vibrational spectrum. Comparison of the results of the VTE LiNbO 3 with those of the congruent crystal and congruent composition melt added 6 wt% K 2 O. In all cases the Li 2 O content was found to be closer to 50% than that of the congruent composition melt added 6 wt% K 2 O. The homogeneity of the composition in the crystal was also investigated. The data presented in this work show that the VTE method can be effectively applied to produce LiNbO 3 stoichiometric crystal.

The Hekpoort paleosol profile in Strata 1 at Gaborone, Botswana: Soil formation during the Great Oxidation Event

The Hekpoort paleosol is a regional paleoweathering horizon developed on the approximately 2.25 Ga Hekpoort basalt of the Transvaal Supergroup, South Africa. A core (Strata 1) through the Hekpoort paleosol near Gaborone, Botswana, is the most complete section through this paleosol. An uppermost ferricrete layer (∼40 cm) is followed by a mottled zone (∼2.0 m), an iron-depleted sericite-rich zone (∼2.3 m), and a FeO-enriched, chlorite-quartz zone (∼13 m), which grades downward into the Hekpoort basalt. The near-constancy of the mole ratios of Al, Zr, Nb, Hf and Th to Ti indicates that these elements were essentially immobile during the formation of the paleosol. Mg, Zn and Mn were largely removed from the upper portion of the soil and were partly reprecipitated in the chlorite zone. Fe²⁺, Co, Ni, V, Cr and U were depleted in the mottled and sericite zones, and were enriched in the ferricrete layer and in the chlorite zone. The vertical distribution of the major and trace redox-sensitive elements in Strata 1 indicates that the Hekpoort paleosol developed during the Great Oxidation Event (G.O.E.). The atmosphere must have contained some oxygen, but apparently not enough to oxidize all of the Fe²⁺ released during weathering to Fe³⁺. A mass balance calculation suggests a value of P_O₂ between 2.5x10^-4 and 9x10^-3 atm during the formation of the paleosol. Interpretations of the paleosol as a ground water laterite developed under a highly oxygenated atmosphere are difficult to reconcile with the distribution of the major and trace elements in Strata 1.

Major and trace element variation in ilmenite in the Skaergaard Intrusion: petrologic implications

Ilmenite separates from the floor (LS), roof (UBS), and wall (MBS) sequences of the Skaergaard Intrusion were analyzed for major and trace elements using DCP-AES and ICP-MS techniques. In all three sequences, FeO progressively increases, and MgO and Al2O3 progressively decrease with differentiation. Although trace element abundances are, in general, higher in UBS ilmenite than in MBS and LS ilmenite, all three sequences have similar trends for trace element abundance vs. crystallization. Ba, Cs, Rb, Sr, Th, U, Y, and the REEs are excluded elements in ilmenite, and remained at low abundances during differentiation. Cr, Ni, Sc, and V are included elements in ilmenite and other mafic phases, and decreased during differentiation. V contents in ilmenite, however, do not decrease significantly until the upper part of the middle zone, suggesting that magnetite did not begin to affect the magma differentiation trend until much later than when it first appears in the intrusion. Hf, Nb, Ta, and Zr, which are strongly excluded elements in silicates, are included elements in ilmenite. The element ratios Zr/Hf, Y/Ho, Nb/Ta, and U/Th are relatively constant in Skaergaard ilmenite from different parts of the intrusion, suggesting that fluid transport did not significantly effect these elements during differentiation or post-solidification cooling. Calculated partition coefficients for ilmenite in the Skaergaard Intrusion are similar to those reported from previous studies of lunar and terrestrial basalts and kimberlites, and for most elements are significantly lower than those reported for ilmenite in rhyolitic magma. Similar Di's for Zr, Hf, Nb, and Ta suggest that ilmenite crystallization did not significantly affect Zr/Nb or Hf/Ta in the Skaergaard magma, but the ratios of Zr, Hf, Nb, or Ta to other high field strength elements, such as Th, U, Y, or the REEs, may have been altered by ilmenite fractionation.

Cenozoic magmatism in the western Ross Embayment: Role of mantle plume versus plate dynamics in the development of the West Antarctic Rift System

Geochemical and chronological data for Cenozoic plutons and dikes from northern Victoria Land (Antarctica), were used to propose a tectonic‐magmatic model for this portion of the West Antarctic Rift System (WARS). The seven major plutons are compositionally bimodal, with gabbroic and syenitic portions. Among the 180 studied dikes, most are 1 m thick and have alkali basalt‐basanite‐tephrite compositions, along with minor intermediate rocks. Trachytic‐rhyolitic dikes (up to 50 m thick) are by far less common. The 40Ar‐39Ar data for dikes indicate middle Eocene to early Oligocene ages, the oldest found to date for igneous activity throughout the WARS. The geochronological‐structural framework provides evidence for coeval emplacement of dikes on two main NW‐SE and N‐S striking trends, whereas plutonic‐subvolcanic activity occurred in adjacent crustal sectors at different times. Mafic dikes display major and trace element distribution typical of basalts from oceanic islands, such as high ratios of Nb and Ta to large ion lithophile and heavy rare earth elements, coupled with prominent negative K and Pb anomalies in the primitive mantle‐normalized multielement diagrams. Initial isotopic compositions are within the ranges of 0.70299–0.70372 for 87Sr/86Sr and 4.2–6.3 for εNd. These features are shared by younger Neogene lavas. Geochemical modeling for both mafic dikes and lavas indicates an enriched magma source characterized by a residual potassic hydrous phase, thus pointing out a mantle source nearly uniform throughout 50 m.y. Comparable geochemical signature are reported for the magma source of the other Cenozoic volcanic provinces of the WARS and the whole Antarctic Plate. The new data for the early igneous rocks of the rift put in evidence a chronologic‐structural link between magmatic evolution, regional tectonics and plate dynamics which suggests a model for WARS magmatism that is alternative to current plume hypotheses. We propose that magma genesis and emplacement are related to reactivation of preexisting translithospheric faults, which promoted local decompression melting of an enriched mantle that was previously veined during the decompression episode associated with the amagmatic late Cretaceous extensional rift phase.

Compositional Studies on the Electronic and Magnetic Properties of Potassium Fulleride Mesoporous Niobium Oxide Composites

Mesoporous niobium oxide potassium fulleride composites were synthesized by the treatment of mesoporous niobium oxide with 0.3, 0.6, or 1.0 equiv of potassium naphthalene followed by stirring with either excess K3C60 or C60. The reaction of potassium-reduced mesoporous niobium oxide with neutral C60 is the first reported example of a mesoporous oxide functioning as an electron donor to a guest molecule. These new routes allow for greater flexibility in the K:Nb and C:Nb ratios in the composite than our previous method and for this reason enables a more comprehensive study of the effect of absolute carbon and potassium content on electron transport properties. Materials were characterized by elemental analysis, nitrogen adsorption, XRD, XPS, SQUID magnetometry, and room-temperature conductivity measurements in an effort to relate density of states at the Fermi level, temperature-independent paramagnetism, and conductivity patterns to the composition of the composite. Variable temperature resistivity measur...

The systematics of boron isotopes in Izu arc front volcanic rocks

The process of fluid release from the subducting slab beneath the Izu arc volcanic front (Izu VF) was examined by measuring B concentrations and B isotope ratios in the Neogene fallout tephra (ODP Site 782A). Both were measured by secondary ion mass spectrometry, in a subset of matrix glasses and glassy plagioclase-hosted melt inclusions selected from material previously analyzed for major and trace elements (glasses) and radiogenic isotopes (Sr, Nd, Pb; bulk tephra). These tephra glasses have high B abundances (∼10–60 ppm) and heavy δ 11B values (+4.5‰ to +12.0‰), extending the previously reported range for Izu VF rocks (δ 11B, +7.0‰ to +7.3‰). The glasses show striking negative correlations of δ 11B with large ion lithophile element (LILE)/Nb ratios. These correlations cannot be explained by mixing two separate slab fluids, originating from the subducting sediment and the subducting basaltic crust, respectively (model A). Two alternative models (models B and C) are proposed. Model B proposes that the inverse correlations are inherited from altered oceanic crust (AOC), which shows a systematic decrease of B and LILE with increasing depth (from basaltic layer 2A to layer 3), paralleled by an increase in δ 11B (from ∼+1‰ to +10‰ to +24‰). In this model, the contribution of sedimentary B is insignificant (<4% of B in the Izu VF rocks). Model C explains the correlation as a mixture of a low-δ 11B (∼+1‰) ‘composite’ slab fluid (a mixture of metasediment- and metabasalt-derived fluids) with a metasomatized mantle wedge containing elevated B (∼1–2 ppm) and heavy δ 11B (∼+14‰). The mantle wedge was likely metasomatized by 11B-rich fluids beneath the outer forearc, and subsequently down dragged to arc front depths by the descending slab. Pb–B isotope systematics indicate that, at arc front depths, ∼53% of the B in the Izu VF is derived from the wedge. This implies that the heavy δ 11B values of Izu VF rocks are largely a result of fluid fractionation, and do not reflect variations in slab source provenance (i.e. subducting sediment vs. basaltic crust). Since the B content of the peridotite at the outer forearc (7–58 ppm B, mean 24±16 ppm) is much higher than beneath the arc front (∼1–2 ppm B), the hydrated mantle wedge must have released a B-rich fluid on its downward path. This ‘wedge flux’ can explain (1) the across-arc decrease in B and δ 11B (e.g. Izu, Kuriles), without requiring a progressive decrease in fluid flux from the subducting slab, and (2) the thermal structure of volcanic arcs, as reflected in the B and δ 11B variations of volcanic arc rocks.

Variations in Electrical Properties of Nb-Doped SrTiO 3 with Cation Nonstoichiometry

The influences of Sr/(Ti+Nb) ratios on the electrical properties of Nb-doped SrTiO 3 ceramics have been investigated. Regardless of Sr/(Ti+Nb) ratios, the appearance of non-linearity in the current-voltage characteristics was observed. When Sr/(Ti+Nb) ratio is lower than 1.000, the results acquired from impedance analysis revealed that the activation energies for carrier conduction were determined to be 0.83 eV in grains and 1.67 eV in grain boundaries. Otherwise, the specimens with Sr/(Ti+Nb) S 1.004 showed energies of 0.80 eV in grains and 1.27 eV in grain boundaries. From these measured results, it was suggested that the activation energies, about 0.80 eV, measured in grains were originated from oxygen vacancies and the activation energies, 1.27 and 1.67 eV, measured in grain boundaries were from titanium and strontium vacancies, respectively.

Compositional recycling structure of an Archean super-plume: Nb–Th–U–LREE systematics of Archean komatiites and basalts revisited

The volcanic stage of the 2.7-Ga Abitibi greenstone belt, Canada, is dominated by bimodal arc magma series and komatiite–basalt sequences. The latter represents an aerially extensive oceanic plateau erupted from an anomalously hot super-plume. Komatiites define a linear array of Nb/Th vs. Nb/U, extending from Nb/Th=8–20, and Nb/U=26–58, whereas basalts plot on a separate, but overlapping, field extending to higher Th/U but lower Nb/Th values. Inter-element ratios of Th, U, Nb, and LREE of komatiites and basalts plot with Phanerozoic and modern ocean plateau basalts. Th, U, Nb, and LREE are fractionated in subduction zones into low Nb/Th, Nb/U, and Nb/LREE arc crust, and complementary high Nb/Th, Nb/U, and Nb/LREE residual slab. Accordingly, the Archean komatiite–basalt association may be explained by a plume that likely originated from the core–mantle boundary with komatiites erupted from a hot axis containing recycled oceanic crust, and basalts erupted from the plume annulus that entrained upper mantle containing recycled oceanic and continental crust. High Nb/Th and Nb/U of plume-related volcanic sequences documented in Abitibi, Yilgarn, and Baltic Archean greenstone belts suggest that the extraction and recycling of continental crust may have occurred early in the Archean.

Composition control of SBN thin films deposited by PLD on various substrates

Thin films of SrBi2Nb2O9 (SBN) have been grown on both Pt/Ti/SiO2/Si and (100)MgO substrates by pulsed laser deposition. In the Sr–Bi–Nb–O system, the loss of bismuth during the process due to its volatility results obviously in a non-respect of the stoichiometry of the films and the presence of secondary phases. In order to maintain the right composition of the films, two different ways were experimented. On Pt/Ti/SiO2/Si, a sequential deposition from home-made Bi2O3 and SBN sintered targets as well as the use of Bi-enriched targets allows to obtain stoichiometric ferroelectric films. Various parameters like deposition time and periodicity of the Bi2O3 and SBN layers are of first importance. On (100)MgO which promotes SBN epitaxial growth, this sequential deposition is not suitable and we succeeded in the control of the Bi/(Sr+Nb) ratio only by using Bi-enriched targets.

Single Crystal Growth and Characterizations of A3BC3D2O14-Type Compounds for Piezoelectric Applications

A3Nb1-xGa3+(5/3)xSi2O14 (ANGS, A=Sr, Ca) compounds were investigated as a function of Nb and Ga mole ratios and grown using the micro pulling-down (µ-PD) technique after being prepared by the conventional solid-state reaction. On the basis of the µ-PD growth results, ANGS single crystals were grown by the Czochralski method. The grown Sr3NbGa3Si2O14 (SNGS) and Ca3NbGa3Si2O14 (CNGS) the single crystals showed that they were isostructural to that of A3BC3D2O14, which had the space group P321. The lattice parameters of SNGS and CNGS were calculated to be a=8.282, 8.087 and c=5.073, 4.980 Å, respectively. The defect distribution and piezoelectric properties of these crystals were measured.

Epitaxial growth of orientation-controlled KNbO3 crystal films on MgO using KTaxNb1−xO3 intermediate layer by metalorganic chemical vapor deposition

In this letter, we report a method to obtain an orientation-controlled (010) KNbO3 crystal film on (110) MgO substrate based on the epitaxial growth by the low-pressure metalorganic chemical vapor deposition. In order to control the orientation of the KNbO3 film, an intermediate layer of KTaxNb1−xO3 was used. In the case where the Ta/(Ta+Nb) ratio of the KTaxNb1−xO3 film was over 40%, we could obtain (010)-oriented epitaxial KNbO3 films. Furthermore, the surface morphology of the deposited film, the thickness of which was about 1 μm, was smooth at the Ta/(Ta+Nb) ratio of 60%. The measurement of the refractive index dispersion of the KNbO3 crystal film was also carried out.

Superparamagnetic and spin glass behavior in mesoporous niobium oxide bis(cyclopentadienyl)nickel composites

Herein we report the synthesis and characterization of a new family of mesoporous niobium oxide bis(cyclopentadienyl)nickel composites which exhibit superparamagnetic or spin glass behavior depending on the different loading levels of the organometallic in the pores. XRD and nitrogen adsorption studies confirm the retention of the mesostructure in these new materials upon introduction of the guest species. The Nb 3d region of the XPS provides evidence for the slight reduction of the Nb(V) oxide walls while the Ni 2p region shows the presence of both neutral and cationic bis-cyclopentadienyl nickel species with peaks at 856.3 eV and 861.9 eV respectively, as well as two more highly oxidized species at 865.5 eV and 867.3 eV. The presence of neutral and cationic bis(cyclopentadienyl)nickel is further confirmed by EPR. SQUID magnetic measurements show superparamagnetic behavior for the material with a Ni∶Nb ratio of 0.07∶1, while at a ratio of 0.1∶1 the material shows spin glass behavior, a phenomenon normally associated with amorphous metal alloys. The difference in magnetic behavior is rationalized by an increased density of unpaired spins in the pore structure.

Crystal structure of a strontium–tantalum and a magnesium–niobium heterometal alkoxide: precursors for the MOCVD of ferroelectric oxides

The heterometal alkoxides Sr[Ta(OPri)6]2·2PriOH 1 and Mg[Nb(OEt)6]2·2EtOH 2 have been structurally characterised by X-ray diffraction. Compound 1 is a precursor for the deposition of strontium bismuth tantalate (SrBi2Ta2O9) by metalorganic chemical vapour deposition (MOCVD), whilst 2 is a potential precursor for the MOCVD of lead magnesium niobate [Pb(Mg0.33Nb0.66)O3]. In this paper it is shown how the presence of Pb(thd)2 (thd = 2,2,6,6-tetramethylheptane-3,5-dionate) significantly influences the deposition chemistry of 2. In the absence of Pb(thd)2 and at low substrate temperatures (ca. 425 °C) the Mg∶Nb ratio in the oxide film grown from 2 is close to 1∶2, whereas at higher substrate temperatures (600 °C) the films are magnesium deficient, indicating partial decomposition of 2. However, in the presence of Pb(thd)2 films grown from 2 at low temperature (425–500 °C) contain no detectable Mg whilst the 1∶2 Mg∶Nb ratio, required in Pb(Mg0.33Nb0.66)O3, is now obtained at higher substrate temperatures (600 °C). This is attributed to the formation of a thermally stable Mg β-diketonate species via a gas-phase ligand exchange reaction between Pb(thd)2 and 2.