Complete Series Of Solid Solutions Research Articles

Phase stability of ternary antifluorite type compounds in the quasi-binary systems Mg2X–Mg2Y (X, Y = Si, Ge, Sn) via ab-initio calculations

A first-principles study of the stability of ternary alloys based on the antifluorite structure with Mg2X chemical formula (X = Si, Ge and Sn) is reported in order to evaluate their potential for high temperature thermoelectric applications. For the end-members, we find that |EformMg2Si|<|EformMg2Sn|<|EformMg2Ge| in good agreement with the values in the literature. We find that only the Mg2Si–Mg2Ge alloys form complete series of solid solutions. This result agrees with published experimental results and CALPHAD assessments. We find that Mg2Si–Mg2Sn and Mg2Ge–Mg2Sn systems display a miscibility gap. Therefore, for the Mg2Si–Mg2Sn based alloys, our results qualitatively confirm a recent reassessment of this quasi-binary phase diagram done by Kozlov et al. (J. Alloy Compd509, 3326–3337 (2011)) and suggest that the same kind of quasi-binary phase diagram exists in the case of the Mg2Ge–Mg2Sn alloys with a lower critical demixing temperature. The currently best thermoelectric alloys Mg2Si1−xSnx are most likely a mixture of two-phases and therefore the stability of their thermoelectric properties for long time applications should be carefully studied.

Pronounced site preference and mixed dinuclear dichalcogenide anions (SSe)2− in ternary lanthanum sulfide selenides – The solid solution LaS1.9–LaSe1.9

Ternary lanthanum sulfide selenides LaS1.9−xSex (0 < x < 1.9) were obtained by reaction of the elements in a potassium bromide flux. The ternary compounds adopt the CeSe1.9 structure type (tetragonal, space group P42/n, No. 86) and form a complete solid solution series without indications of ordered superstructures. The lattice parameters of the samples follow Vegard’s rule and are found in the range of 915 ≤ a ≤ 943 pm and 1644 ≤ c ≤ 1703 pm. A pronounced ordering of the distribution of chalcogen atoms is observed which can be attributed to charge density and size effects. The existence of three different types of dichalcogenide anions, namely S22−, Se22− and mixed (SSe)2−, is evidenced by Raman spectroscopy.

Tunability of structure from ordered to disordered and its impact on ionic conductivity behavior in the Nd2−yHoyZr2O7 (0.0 ≤ y ≤ 2.0) system

The present paper describes a detailed investigation of the nature of the order–disorder transition in the Nd2−yHoyZr2O7 system, over the entire composition range (0.0 ≤ y ≤ 2.0), using a combination of diffraction and spectroscopic analysis techniques. The complete series of solid solutions has been prepared by the gel combustion technique followed by high temperature sintering. Detailed structural characterization of the prepared samples using X-ray diffraction studies confirmed their single-phase solid solution formation throughout the series, as well as identifying the transformation of the system from an ordered pyrochlore structure (0.0 ≤ y ≤ 0.8) to a disordered fluorite-type structure (0.8 < y ≤ 2.0). Micro-Raman studies further supported the structural information. Micro-structural studies by SEM revealed dense products with uniform grain distribution in these materials. Comprehensive studies were performed to investigate the ionic conductivity behavior of these solid solutions in correlation with the structural transformations using AC impedance spectroscopy. A detailed analysis of ionic conductivity and related parameters, such as activation energies, etc. corresponding to individual conduction mechanisms such as bulk and grain boundary conduction, clearly correlated the effect of structural transformation on these charge transport properties. The composition Nd1.2Ho0.8Zr2O7 with the pyrochlore structure has been found to show the highest ionic conductivity in the entire series, which has been attributed to a combined effect of increasing carrier concentration and their preferred movement through an ordered array of vacant anion sites.

Structural and magnetic characterization of the complete delafossite solid solution (CuAlO2)1−x(CuCrO2)x

We have prepared the complete delafossite solid solution series between diamagnetic CuAlO2 and the t2g3frustrated antiferromagnet CuCrO2. The evolution with composition x in CuAl1−xCrxO2 of the crystal structure and magnetic properties has been studied and is reported here. The room-temperature unit cell parameters follow the Végard law and increase with x as expected. The μeff is equal to the Cr3+ spin-only S = 3/2 value throughout the entire solid solution. ΘCW is negative, indicating that the dominant interactions are antiferromagnetic, and its magnitude increases with Cr substitution. For dilute Cr compositions, the nearest-neighbor exchange coupling constant JBB was estimated by mean-field theory to be 3.0 meV. Despite the sizable ΘCW, long-range antiferromagnetic order does not develop until x is almost 1, and is preceded by glassy behavior. The data presented here, and those on dilute Al substitution from Okuda et al, suggest that the reduction in magnetic frustration due to the presence of non-magnetic Al does not have as dominant an effect on magnetism as chemical disorder and dilution of the magnetic exchange. For all samples, the 5 K isothermal magnetization does not saturate in fields up to 5 T and minimal hysteresis is observed. The presence of antiferromagnetic interactions is clearly evident in the sub-Brillouin behavior with a reduced magnetization per Cr atom. An inspection of the scaled Curie plot reveals that significant short-range antiferromagnetic interactions occur in CuCrO2 above its Néel temperature, consistent with its magnetic frustration. Uncompensated short-range behavior is present in the Al-substituted samples and is likely a result of chemical disorder.

ChemInform Abstract: Compositionally Controlled Metal—Insulator Transition in Tl2‐xInxTeO6.

AbstractPolycrystalline samples of the complete solid solution series Tl2‐xInxTeO6 (0 ≤ x ≤ 2) are prepared by solid state reaction of stoichiometric mixtures of In2O3, Tl2O3, and TeO2 or H6TeO6 (gold containers, 550—650 °C, 24 h).

Preparation and physical properties of antiperovskite-type compounds CdNCo 3− zNi z (0≤ z≤3)

A series of CdNCo 3− z Ni z (0≤ z≤3) samples were prepared from CdO and metal powders under NH 3 atmosphere at 743 K. The structural and physical properties were investigated by means of X-ray powder diffraction, temperature dependent resistivity and magnetic measurements. X-ray powder diffraction results show that CdNCo 3 is a new ternary nitride with antiperovskite structure, and it can form a complete solid solution series with CdNNi 3. Both CdNCo 3 and CdNNi 3 samples show metallic temperature dependent resistivity and exhibit a Fermi liquid behavior below 50 K. All samples are ferromagnetic, and their coercivity and remanence decrease as the Ni content increases. The temperature dependence of the magnetization of the CdNCo 3− z Ni z samples can be well fitted to the combination of a Bloch term and a Curie–Weiss term. The CdNCo 3 sample is ferromagnet with coercivity of 240 Oe at room-temperature. In contrast to the paramagnetism previously reported, our CdNNi 3 sample exhibits very soft and weak ferromagnetism.

Alkaline-Earth Metal Hydrides as Novel Host Lattices for EuII Luminescence

Luminescence of divalent europium has been investigated for the first time in metal hydrides. A complete solid-solution series was found for the pseudobinary system Eu(x)Sr(1-x)H(2) [a = 637.6(1) pm -12.1(3)x pm, b = 387.0(1)-6.5(2)x pm, c = 732.2(2)-10.1(4)x pm]. Europium-doped alkaline-earth hydrides Eu(x)M(1-x)H(2) (M = Ca, Sr, Ba) with a small europium concentration (x = 0.005) exhibit luminescence with maximum emission wavelengths of 764 nm (M = Ca), 728 nm (M = Sr), and 750 nm (M = Ba); i.e., the emission energy of divalent europium shows an extremely large red shift compared to the emission energies of fluorides or oxides. Theoretical calculations (LDA+U) confirm decreasing band gaps with increasing europium content of the solid solutions.

Electrical and magnetic properties of the complete solid solution series between SrRuO3and LaRhO3: Fillingt2gversus tilting

A complete solid solution series between the t2g^4 perovskite ferromagnet SrRuO3 and the diamagnetic t2g^6 perovskite LaRhO3 has been prepared. The evolution with composition x in (SrRuO3)(1-x)(LaRhO3)(x) of the crystal structure and electrical and magnetic properties has been studied and is reported here. As x increases, the octahedral tilt angle gradually increases, along with the pseudocubic lattice parameter and unit cell volume. Electrical resistivity measurements reveal a compositionally driven metal to insulator transition between x = 0.1 and 0.2. Ferromagnetic ordering gives over to glassy magnetism for x > 0.3 and no magnetic ordering is found above 2 K for x > 0.5. M_sat and Theta_CW decrease with increasing x and remain constant after x = 0.5. The magnetism appears poised between localized and itinerant behavior, and becomes more localized with increasing x as evidenced by the evolution of the Rhodes-Wohlfarth ratio. mu_eff per Ru is equal to the quenched spin-only S value across the entire solid solution. Comparisons with Sr(1-x)Ca(x)RuO3 reinforce the important role of structural distortions in determining magnetic ground state. It is suggested that electrical transport and magnetic properties are not strongly coupled in this system.

ChemInform Abstract: Hydrolytic Precipitation of Solid Solutions of Iron(III) and Gallium( III) with Admixture of Fluoride Ions.

Investigations were carried out on the formation of solid solutions of iron(III) and gallium(III) compounds crystallizing from fluoride-containing solutions. Out of a range of many possible solids, the elpasolite type and oxide hydroxides were chosen. The hexafluoride complexes, K2NaMF6, form a complete series of solid solutions. There is also a complete solubility series for the oxide hydroxides. Crystallization from a pure solution of iron(III) salt leads to the formation of β-FeOOH(F), in which up to 50 mol.% of iron(III) can be substituted by gallium(III). Higher proportions of gallium result in oxide hydroxides with a diaspore structure. The high fluoride content in these compounds is thought to be due to substitution of hydroxide ions by fluoride.

Platinum-group minerals and tellurides from the PGE-bearing Xinjie layered intrusion in the Emeishan Large Igneous Province, SW China

The Xinjie layered intrusion is one of a number of major ultramafic-mafic bodies hosting Fe-Ti-V deposits and Cu-Ni-PGE sulfide deposits in the Pan-Xi (Panzhihua-Xichang) area of the Sichuan Province, SW China. The Xinjie ultramafic-mafic layered intrusion, genetically related to the Permian plume-related Emeishan flood basalts, consists of three lithological cycles, each representing a sequence from ultramafic to mafic-felsic composition. The basal part of the intrusion is composed of three lithological units, namely, the Marginal Unit (MU), Peridotite Unit (PeU) and Pyroxenite Unit (PyU). In the present study, three major PGE-mineralised Cu-Ni sulfide layers were discovered within the Marginal and Pyroxenite Units. The major base-metal sulfides (BMS) comprise chalcopyrite, pyrrhotite, and pentlandite. Detailed microscopic and microprobe analyses revealed the presence of the sperrylite and Pd-Pt-Bi-Te minerals (merenskyite, moncheite, and michenerite). These PGMs are commonly associated with the BMS, or magnetite coexisting with BMS in the PGE-enriched layers. The 1:1 substitution between Pt and Pd, as well as between Te and Bi, confirms the complete solid-solution series between moncheite and merenskyite. The textural association of the PGMs with BMS and Fe-Ti oxides (magnetite) suggests that the PGMs may have crystallised slightly later than the hosting magnetite and BMS. The formation of magnetite may have played an important role in producing the sulfur-saturated melt and the PGEs thus concentrated in the sulfide liquid during the crystallisation history. It is therefore suggested that the Cu-Ni-PGE-bearing layers in the basal part of the Xinjie intrusion were generated by magma evolution processes.

Structural, electronic and optical properties of the wide-gap [formula omitted] ternary alloys

The II–VI compounds CdTe and ZnTe form a complete series of solid solutions with a cubic Zinc Blende structure. The room temperature band gap of these materials can be tuned from 1.5 eV in CdTe to 2.3 eV in ZnTe by controlling the alloy composition. This material is used as the window layer in thin-film solar cells. Using first-principles calculations, we investigated the structural and electronic properties of two binary CdTe and ZnTe for several compositions with various ordered structures (Cu 3Au, luzonite) of Zn 1− x Cd x Te alloys using the theory of order–disorder transformation. An investigation was also conducted using the first-principles total-energy formalism based on the hybrid full potential augmented plane wave plus local orbital (APW+ lo) method, within the local-density approximation (LDA) for the exchange and correlation potential. The 3d orbitals of the Zn atoms and 4d orbitals of the Cd atoms were treated as valence bands in every case. We analyzed the effect of alloying a small amount of ZnTe with CdTe; the fundamental direct band gap energy of the alloys was found to decrease per atomic percent of cadmium.

Synthetic SrCa margarite, anorthite and slawsonite solid solutions and solidfluid SrCa fractionation

Calcium-strontium solid-solutions of margarite, anorthite, slawsonite, calcite and strontianite were synthesized from oxide-hydroxide-fluid mixtures by way of hydrothermal experiments at 400-500 °C and 390-500 MPa. The fractionation of Ca and Sr between the coexisting phases was investigated via electron microprobe and X-ray diffraction analyses of the solids and inductively coupled plasma-optical emission spectrometry of the fluids. A complete solid-solution series of margarite is indicated and the lattice parameters a, b, c, and V increase linearly with increasing Sr content. The lattice parameters of (Ca,Sr)-anorthite show a likewise linear increase with increasing Sr content. The formation of Sr-Ca slawsonite and Sr-Ca strontianite is restricted to high bulk Sr contents. The fractionation of Ca and Sr between minerals and fluid expressed as K mineral-fluid D(Sr-Ca) increases in the following sequence: calcite-fluid < anorthite-fluid < margarite-fluid ≈ 1< strontianite-fluid < slawsonite-fluid. At low X Sr (i.e., for common metamorphic bulk-rock compositions), K calcite-fluid D(Sr-Ca) = 0.09, K anorthite-fluid (Sr-Ca) = 0.51, and K margarite-fluid (Sr-Ca) = 0.56; the Sr/Ca ratio of the fluid is therefore generally higher than that of the coexisting minerals. This suggests that during prograde metamorphism and probably continuous dehydration, the Sr/Ca ratio of the rock decreases continuously with time. But, owing to the roughly equal Sr-Ca mineral-fluid fractionation for margarite and anorthite, which was also determined for zoisite/clinozoisite and lawsonite, this decrease will result in only moderate changes of whole-rock and fluid Sr-composition as long as these phases are the main Sr-bearing minerals.

The constitution of the ternary system Fe–Ni–Si

The ternary system Fe–Ni–Si was investigated using X-ray diffraction (XRD), metallography (SEM), energy dispersive spectroscopy (SEM/EDS), magnetic susceptibility measurements, and differential thermal analysis (DTA). The existence of the ternary phase τ is corroborated and its crystal structure is confirmed to be isostructural to Cr 3Ni 5Si 2. At 700 °C the homogeneity of this phase extends from 43 to 55 at.% iron at constant 20 at.% Si. Furthermore, for the binary phases NiSi 2, Ni 2Si and Ni 31Si 12 extensive solubilities for iron are found, while the solubility of Fe in NiSi, Ni 3Si 2 or Ni 3Si does not exceed 5 at.%. On the other side of the system, the phases FeSi and Fe 3Si have large solubilities for Ni, while this is rather limited in FeSi 2. The (binary high temperature) phase Fe 5Si 3 is stabilized by Ni at least down to 700 °C. Tie lines exist between τ and solid solutions based on Fe 3Si, Ni 31Si 12 as well as γ (Ni). DTA measurements for the vertical section Fe 2Si–Ni 2Si strongly indicate that Fe 2Si and θNi 2Si form a complete series of solid solutions θ(Fe, Ni) 2Si and are thus isostructural. A critical evaluation of the available crystal structure data for Fe 2Si supports this assumption. Iron rich θ(Fe, Ni) 2Si is a weak ferromagnet. The magnetic moment of ∼1 μB per Fe-atom in θ(Fe, Ni) 2Si is only half of the magnetic moment per Fe-atom measured for τ Fe 5Ni 3Si 2. A reaction scheme accounting for all DTA data of the entire system is established and in combination with observations on the first crystallizing phase(s) the liquidus surface of Fe–Ni–Si is revised.

COMPOSITIONAL DATA FOR IKUNOLITE FROM REDZINY, RUDAWY JANOWICKIE, LOWER SILESIA, POLAND

The chemical composition of ikunolite and the distribution of Se among various sulfides and sulfosalts at Redziny, in the metamorphic cover of the Variscan Karkonosze pluton, in Lower Silesia, Poland, have been documented by electron-microprobe analysis. At Redziny, selenium becomes concentrated at the lower-temperature stages of mineralization. Its main carrier is ikunolite, Bi 4 (S,Se) 3 , with Se contents up to ca . 11 wt.%. Some grains of Ag-bearing galena and aikinite also may be enriched in Se (above 1 wt.%). The chemical composition of ikunolite shows a wide variability, never reported from any other locality. Results of our analyses document a full range of Se-for-S substitution in ikunolite and the existence of a complete solid-solution series from the sulfur end-member to a composition with a S:Se ratio ca . 1:1. According to data available in the literature, ikunolite also forms a continuous solid-solution series with laitakarite, Bi 4 (Se,S) 3 . Some ikunolite compositions reveal substantial amounts of Pb substituting for Bi, in the range 0–0.46 apfu . One sample has the composition PbBi 3 (S,Se) 3 , indicating a compositional trend towards babkinite, Pb 2 Bi 2 (S,Se) 3 .

Optical birefringence study of the ferroelectric phase transition in lithium niobate tantalate mixedcrystals: LiNb1−xTaxO3

The optical birefringence of a complete solid-solution series of lithium niobate–tantalatecrystals has been measured as a function of temperature. It is found that, irrespective ofcomposition, the high-temperature paraelectric phase has a birefringence close to+0.063, suggesting that this value arises purely from the oxygen octahedra in the crystalstructure. It is also observed that a small addition of lithium niobate to the tantalateproduces a crystal that has zero birefringence at room temperature.

Phase relations on the diopside–jadeite–hedenbergite join up to 24 GPa and stability of Na-bearing majoritic garnet

Phase relations on the diopside (Di)–hedenbergite (Hd)–jadeite (Jd) system modeling mineral associations of natural eclogites were studied for the compositions (mol %) Di 70Jd 30, Di 50Jd 50, Di 30Jd 70, Di 20Hd 80, and Di 40Hd 10Jd 50 using a toroidal anvil-with-hole (7 GPa) and a Kawai-type 6–8 multianvil apparatus (12–24 GPa). We established that Di, Hd, and Jd form complete series of solid solutions at 7 GPa, and melting temperatures of pure Di (1980 °C) and Jd (1870 °C) for that pressure were estimated experimentally. The melting temperature for the Di 50Jd 50 composition at 15.5 GPa is 2270 °C. The appearance of garnet is clearly dependent on initial clinopyroxene composition: at 1600 °C the first garnet crystals are observed at 13.5 GPa in the jadeite-rich part of the system (Di 30Jd 70), whereas diopside-rich starting material (Di 70Jd 30) produces garnet only above 17 GPa. The proportion of garnet increases rapidly above 18 GPa as pyroxene dissolves in the garnet structure and pyroxene-free garnetites are produced from diopside-rich starting materials. In all experiments, garnet coexists with stishovite (St). At a pressure above 18 GPa, pyroxene is completely replaced by an assemblage of majorite (Maj) + St + CaSiO 3–perovskite (Ca-Pv) in Ca-rich systems, whereas Maj is associated with almost pure Jd up to a pressure of 21.5 GPa. Above ∼22 GPa, Maj, and St are associated with NaAlSiO 4 with calcium ferrite structure (Cf). We established that an Hd component also spreads the range of pyroxene stability up to 20 GPa. In the Di 70Jd 30 system at 24 GPa an assemblage of Maj + Ca-Pv + MgSiO 3 with ilmenite structure (Mg-Il) was obtained. The experimentally established correlation between Na, Si, and Al contents in Maj and pressure in Grt(Maj)–pyroxene assemblages, may be the basis for a “majorite” geobarometer. The results of our experiments are applicable to the upper mantle and the transition zone of the Earth (400–670 km), and demonstrate a wide range of transformations from eclogite to perovskite-bearing garnetite. In addition, the mineral associations obtained from the experiments allowed us to simulate parageneses of inclusions in diamonds formed under the conditions of the transition zone and the lower mantle.

THE SULFIDES AND SELENIDES OF THE MUSONOI MINE, KOLWEZI, KATANGA, DEMOCRATIC REPUBLIC OF CONGO

An investigation of ore minerals from the Thrust-Slice “2400’” of the Musonoi Extension mine, Katanga, Democratic Republic of Congo, has provided new insights into the origin of copper sulfides and selenides. The early sulfides are pyrite, covellite, spionkopite, and digenite, which crystallize, with authigenic quartz, during diagenesis. Metasomatic enrichment in U and Se, which is responsible for the unusual mineralogy of the Musonoi deposit, firstly gave rise to the crystallization of Cu–Pd-bearing trogtalite and various palladium selenides (oosterboschite, verbeekite and unidentified Pd–Cu–Pt–Se phases). Subsequently, Se-rich copper minerals, berzelianite and Se-bearing carrollite formed, followed by the crystallization of Se-bearing digenite. Temperature estimates based on these assemblages indicate at least 200°C. Meteoric alteration affected these primary minerals and mainly resulted in the leaching of copper. Replacement phases are spionkopite, yarrowite, and athabascaite, which formed at temperatures below 100°C. Electron-microprobe analyses show the existence of a complete solid-solution series between high digenite and berzelianite. The variation of the a unit-cell parameter along this solid solution follows the equation y = −0.3446 x 3 + 0.5485 x 2 − 0.0358 x + 5.5758, R2 = 0.96. A similar mechanism of S-for-Se substitution accounts for the precipitation of Se-bearing spionkopite and S-bearing athabascaite. These observations provide new data on the sequence of transformation affecting copper sulfides and selenides at low-temperature, meteoric conditions.

Crystal structures and phase transitions of SrZr(PO 4) 2–BaZr(PO 4) 2 solid solutions

A complete series of solid solutions was prepared in the SrZr(PO 4) 2–BaZr(PO 4) 2 system and examined by conventional X-ray powder diffraction (XRPD). The crystals of Sr x Ba 1− x Zr(PO 4) 2 with x⩽0.1 were isomorphous with yavapaiite (KFe(SO 4) 2, space group C2/ m). The solid solution with 0.2⩽ x⩽0.7 has been composed of a new phase, showing a superstructure along the a-axis ( c-axis of the yavapaiite substructure). The crystals with 0.8⩽ x⩽0.9 were composed of both the new phase and the triclinic phase, the latter being isostructural with SrZr(PO 4) 2 ( x=1). The crystal structure of the new phase has been determined using direct methods, and it has been further refined by the Rietveld method. The crystal of Sr 0.7Ba 0.3Zr(PO 4) 2 ( x=0.7) is monoclinic (space group P2/ c, Z=4 and D x /Mg m −3=3.73) with a=1.53370(8) nm, b=0.52991(3) nm, c=0.84132(4) nm, β=92.278(1)° and V=0.68321(6) nm 3. Final reliability indices are R wp=7.32%, R p=5.60% and R B=3.22%. The powder specimen was also examined by high-temperature XRPD and differential thermal analysis (DTA) to reveal the occurrence of two phase transitions during heating; the space group changed from P2/ c to C2/ m at ∼400 K, followed by the monoclinic-to-hexagonal (or trigonal) transition at 1060 K. The P2/ c-to- C2/ m transition has been, for the first time, described in the yavapaiite-type compounds.

Structural and magnetic properties of Cu–Ni–Cr spinel oxides

The compounds CuCr 2O 4 and NiCr 2O 4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I4 1/amd, with axes ratio c/ a<1 and >1, respectively. The distortion is caused by the Jahn–Teller ions Cu 2+ and Ni 2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr 2O 4 and NiCr 2O 4 form a complete solid solution series Cu 1− x Ni x Cr 2O 4 where for 0.825< x<0.875 members with orthorhombic symmetry were found. Using neutron powder diffraction and thermal analysis methods several members of the solid solution series were investigated. On cooling, all samples showed a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr 2O 4) and 310 K (NiCr 2O 4). The phase Cu 0.15Ni 0.85Cr 2O 4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.

Synthesis and ionic conductivity of PbBi 6M 2O 15 (M=V, P, As) and SrBi 6V 2O 15 solid solutions

PbBi 6V 2O 15, PbBi 6P 2O 15, PbBi 6As 2O 15 and their solid solutions have been prepared by the mixed oxide route at 800–850 °C. Complete solid solutions were formed in the systems PbBi 6V 2O 15–PbBi 6P 2O 15, PbBi 6V 2O 15–PbBi 6As 2O 15 and PbBi 6P 2O 15–PbBi 6As 2O 15. In addition, substitution of Pb by Sr in PbBi 6V 2O 15 resulted in a complete solid solution series. The composition and phase purity of PbBi 6V 2O 15 and the hitherto unreported SrBi 6V 2O 15 were confirmed by electron probe microanalysis (EPMA). Although their crystal structures remain unknown, all compositions appeared to be isostructural from X-ray diffraction (XRD) results and the data could be indexed on an orthorhombic cell derived from the cubic δ-Bi 2O 3 structure, with a∼23.9, b∼17.1 and c∼11.1 Å. Impedance spectroscopy and transference number measurements show these materials to be moderate oxide ion conductors with bulk conductivities of 5×10 −5–10 –7 S cm −1 at 500 °C with transference numbers ∼0.8 at 600–700 °C. Conductivity decreased in the order SrBi 6V 2O 15≫PbBi 6V 2O 15>PbBi 6As 2O 15>PbBi 6P 2O 15 indicating that lone pair electron effects associated with Pb 2+ and cation size effects associated with V, As and P play an important role in controlling the anion transport in these materials.