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[Abstract] In this work we focus in setting the limits of the tolerance factor and the size of the A-cations that stabilize the perovskite structure in hybrid dicyanamide compounds [A][Mn(dca)3]. For this purpose, we propose an alternative, simple approach to calculate a more realistic effective ionic radius for the large and anisotropic A-cations often present in these type of compounds. We test the proposed procedure by analysing the crystal structures of [A][Mn(dca)3] dicyanamide hybrids reported in the literature and recalculating the tolerance factors of such compounds, as well as by preparing five new [A][Mn(dca)3] members, discussing also the influence of the A-cation shape in the stability limits of the perovskite structure. Interestingly, such methodology is not only useful to develop new compounds of the emerging family of (multi)functional multi(stimuli)-responsive dicyanamide materials but can also be applied to other hybrid organic-inorganic perovskites and related materials. As for financial support, the authors thank Ministerio de Economía y Competitividad MINECO and EU-FEDER (projects MAT2017-86453-R and PDC2021-121076-I00), and Xunta de Galicia for the collaboration agreement “Development of research strategic actions Universidade da Coruña I ​+ ​D ​+ ​i 2021–2022: CICA-Disrupting Projects 2021SEM-A3 (NanoCool). J.G.-B. and J.M.B.-G. acknowledge Xunta de Galicia for Predoctoral and Postdoctoral Fellowships, respectively. I.D.-F thanks Ministerio de Universidades for a FPU Predoctoral Fellowship. A. G.-F. and U.B.C thank the Carl Tryggers foundation and the Göran Gustafsson foundation for financial support

In this work, we study the structural changes of the polar [NH4][Cd(HCOO)3] hybrid perovskite under external hydrostatic pressure. We report a reversible framework rearrangement as a function of pressure characterized by: (i) a gradual modification of one formate ligand, which changes its coordination mode from a bridging syn–anti mode at atmospheric pressure (LP-phase) to a chelating-anti mode at high-pressure (HP-phase) and (ii) a change in the coordination of the Cd2+ cations from six-coordinated (LP-phase) to hepta-coordinated (HP-phase). Very interestingly, this unprecedented framework arrangement displays a large electrical polarization. For instance, the polarization value observed at p = 17.7 GPa is about four times the polarization at atmospheric pressure. Therefore, we report that the external pressure induces a novel framework rearrangement in the polar [NH4][Cd(HCOO)3] hybrid perovskite with enhanced electrical polarization. This structure–property relationship offers new insights for designing novel ferroelectric materials based on pressure-responsive hybrid perovskite materials.

In Solid-State Chemistry, a well-known route to obtain new compounds and modulate their properties is the formation of solid solutions, a strategy widely exploited in the case of classical inorganic perovskites but relatively unexplored among emergent hybrid organic–inorganic perovskites (HOIPs). In this work, to the best of our knowledge, we present the first dicyanamide-perovskite solid solution of [TPrA][Co0.5Ni0.5(dca)3] and study its thermal, dielectric and optical properties, comparing them with those of the parent undoped compounds [TPrA][Co(dca)3] and [TPrA][Ni(dca)3]. In addition, we show that the prepared doped compound can be used as a precursor that, by calcination, allows CNTs with embedded magnetic Ni:Co alloy nanoparticles to be obtained through a fast and much simpler synthetic route than other complex CVD or arc-discharge methods used to obtain this type of material.

We have prepared two new lead halides with the novel general formula of DMA7Pb4X15 (DMA = [(CH3)2NH2]+ and X = Cl– or Br–) by using an easy route under mild conditions at room temperature. These compounds exhibit an unprecedented crystal structure, are formed by layers of distorted [PbX6] octahedra, which share corners and faces, and contain intercalated DMA cations. Very interestingly, they display dielectric transitions, which are related to a partial order–disorder process of the DMA cations between 160 and 260 K. Additionally, these new layered hybrids exhibit a broadband photoluminiscent emission, which is related to the structural distortions of the [PbX6] octahedra. These findings not only open up large possibilities for future optoelectronic applications of these materials, but they also offer a novel playground for an easy modulation of electrical and optical properties of hybrid organic–inorganic materials. We anticipate that this novel A7Pb4X15 formula can be adequate to tune the family of the ...

Cs23Mn16O23 was synthesized via the azide/nitrate route from mixtures of Mn2O3, CsNO3, and CsN3. This manganese(II/III) mixed-valent oxide, which contains only one Mn3+ besides 15 Mn2+ cations, was studied by single-crystal X-ray diffraction and magnetic susceptibility measurements. Its crystal structure [P1, Z = 1, a = 1114.26(2), b = 1185.53(2), c = 1205.39(2) pm, α = 70.596(1), β = 80.377(2), γ = 83.072(2)°, R1 = 0.033] is based on a honeycomb-like arrangement of cesium atoms, providing the space for two different types of one-dimensional polyoxomanganate anions, illustrated by the syntax Cs23[MnO2]4[Mn3O5]4. Magnetic susceptibility measurements indicate dominant antiferromagnetic intra-chain interactions present already at ambient temperature and long range inter-chain magnetic ordering at 11 K.

In this work, we focus on [(CH3)2NH2]PbI3, a member of the [AmineH]PbI3 series of hybrid organic–inorganic compounds, reporting a very easy mechanosynthesis route for its preparation at room temperature. We report that this [(CH3)2NH2]PbI3 compound with 2H-perovskite structure experiences a first-order transition at ≈250 K from hexagonal symmetry P63/mmc (HT phase) to monoclinic symmetry P21/c (LT phase), which involves two cooperative processes: an off-center shift of the Pb2+ cations and an order–disorder process of the N atoms of the DMA cations. Very interestingly, this compound shows a dielectric anomaly associated with the structural phase transition. Additionally, this compound displays very large values of the dielectric constant at room temperature because of the appearance of a certain conductivity and the activation of extrinsic contributions, as demonstrated by impedance spectroscopy. The large optical band gap displayed by this material (Eg = 2.59 eV) rules out the possibility that the observ...

By a wet-chemistry route we have been able to effectively dope the CHA2PbBr4 compound, a ferroelectric compound with photovoltaic effect, with different amounts of Mn2+ obtaining three pure compounds CHA2Pb1-xMnxBr4 with x = 0.05, 0.07 and 0.11. At room temperature the crystal structure of these new Mn-doped compounds present an orthorhombic symmetric with polar space group Cmc21, as in the case of the undoped compoud (x = 0). Very interestingly, the doped compounds exhibit a broad PL emissions at room temperature, with a maximum around 605 nm and a long PL lifetime (~0.55 ms), whose intensity increases further upon cooling. The observed PL emission is induced from an energy transfer from host semiconductor to the d-orbitals of Mn2+ cation. In addition, we have explored the capability of these materials to act as chemical sensors for volatile organic compounds and report the selective luminescence vapochromic response in this family of compounds. Therefore, the here presented Mn-doped CHA2Pb1-xMnxBr4 compounds belong to the scarce and desirable group of multifunctional materials, where not only ferroelectric and photovoltaic properties can coexist but also photoluminescence and vapochromic properties, rendering them extremely interesting for a large number of potential practical applications.

In this work we prepare and study the M(dca) 2 pyz compounds, where dca = polar dicyanamide N(CN) 2 − ligand, pyz = pyrazine (C 4 H 4 N 2 ) ligand and M = Fe 2+ , Co 2+ and Zn 2+ that, according to DSC display a first order phase transition, at T t ∼ 270 K (Fe), ∼250 K (Co) and ∼240 K (Zn). Very interestingly these compounds, which consist of a rather robust framework with incorporated polar dca ligands, and which does not host guest species in the cavities of the structure, display a dielectric anomaly associated to such phase transition. This latter in fact corresponds to the structural transition from the disordered HT-phase (space group Pnma ) to the ordered LT-phase (space group P 2 1 / n ). From a detailed analysis of the dipole distributions in each of these crystal structures we conclude that the polar dca ligands, which bridge two transition metal cations, display a cooperative electrical arrangement, in which the dipoles of each of the two interpenetrated networks show a ferroelectric (FE) arrangement; nevertheless, the relative antiparallel orientation of both networks finally results in net antiferroelectric (AFE) arrangements both in the LT- and HT-polymorphs. Very interestingly, the dynamic disorder of the dca ligands at T t gives rise to the observed dielectric anomaly. These materials constitute, therefore, an example of hybrid organic–inorganic compounds where the dielectric response directly arises from the framework –and not from polar guest species– which is a very interesting and novel approach in the search for materials in which the dielectric and magnetic properties can couple more strongly.

In this work, we have successfully synthesized hollow microtubular crystals of the metal–organic framework (MOF) [Co2(NH2-bdc)2(dabco)]·[G] {G = H2O, N,N-dimethylformamide (DMF); NH2-bdc =2-amino-1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane} by a very simple coordination-modulation method that avoids the use of an external modulator. Additionally, we have obtained the corresponding hollow microtubular crystals of Co3O4 through the solid-state thermolysis of the Co-MOF material at 400 °C. The as-prepared Co3O4 crystals exhibit the typical magnetic behavior for a nanostructured material with good crystallinity. Thus, this coordination-modulation method provides a simple route for the preparation of nanostructured porous frameworks and derived oxides and opens a way to prepare new materials with advanced properties.

We report on the hybrid inorganic-organic ammonium compound [NH4][Cd(HCOO)3], which displays a most unusual framework structure: instead of the expected 4(9)·6(6) topology, it shows an ABX3 perovskite architecture with the peculiarity and uniqueness (among all the up-to-date reported hybrid metal formates) that the Cd ions are connected only by syn-anti formate bridges, instead of anti-anti ones. This change of the coordination mode of the formate ligand is thus another variable that can provide new possibilities for tuning the properties of these versatile functional metal-organic framework materials. The room-temperature crystal structure of [NH4][Cd(HCOO)3] is noncentrosymmetric (S.G.: Pna21) and displays a polar axis. DFT calculations and symmetry mode analysis show that the rather large polarization arising from the off-center shift of the ammonium cations in the cavities (4.33 μC/cm(2)) is partially canceled by the antiparallel polarization coming from the [Cd(HCOO)3](-) framework, thus resulting in a net polarization of 1.35 μC/cm(2). As shown by second harmonic generation studies, this net polarization can be greatly increased by applying pressure (Pmax = 14 GPa), an external stimulus that, in turn, induces the appearance of new structural phases, as confirmed by Raman spectroscopy.

We have found that the hybrid organic-inorganic perovskite-like formate Mn(HCOO)(3)[(CH(3))(2)NH(2)] shows a dielectric transition around 190 K. According to single crystal X-ray diffraction, the compound shows rhombohedral symmetry at room temperature and monoclinic symmetry at low temperature (100 K), and the main difference between both structures is that the (CH(3))(2)NH(2)(+) (DMA) cations are disordered in the high temperature phase but cooperatively ordered in the low temperature one. The vibrational spectra of this compound reveal that significant changes take place in the vibrations ascribed to the DMA cation (changes in the frequency of certain vibrations, splitting of particular vibrations, and changes in the intensities), while no significant changes have been observed in those attributed to the formate anion. On the basis of all this information, we attribute the origin of the dielectric transition to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectric transition.

A multistimuli response to temperature and pressure is found in the hybrid inorganic–organic perovskite-like [TPrA][Mn(dca)3] compound, which is related to a first-order structural phase transition near room temperature, Tt ≈ 330 K. This phase transition involves a transformation from room temperature polymorph I, with the noncentrosymmetric space group P4̅21c, to the high temperature polymorph II, with the centrosymmetric space group I4/mcm, and it implies ionic displacements, order–disorder phenomena, and a large and anisotropic thermal expansion (specially along the c-axis). As a consequence, [TPrA][Mn(dca)3] exhibits a dielectric anomaly, associated with the change from a cooperative to a noncooperative electric behavior (antiferroelectric (AFE)–paraelectric (PE) transition). The former implies an AFE distribution of electric dipoles in polymorph I, related to the described off-shift of the apolar TPrA cations and the order–disorder of the polar dca ligands mechanisms, that are different from those reported, up to now, for others perovskite-type hybrid compounds. Such cooperative electric order, below Tt ≈ 330 K, coexisting with long-range antiferromagnetic ordering below T = 2.1 K render the [TPrA][Mn(dca)3] a new type-I multiferroic material. In addition, the obtained experimental results reveal that this compound is also a multistimuli-responsive material, with a very large sensitivity toward temperature and applied external pressure, δTt/δP ≈ 24 K kbar–1, even for small values of pressure (P < 2 kbar). Therefore, this material opens up a potential interest for future technological applications, such as temperature/pressure sensing., The authors are grateful for the financial support from Ministerio de Economia y Competitividad MINECO (MINECO) ENE2014-56237-C4-4-R and Xunta de Galicia under the project GRC2014/042. J. M. B.-G. also wants to thank Barrié Foundation for a predoctoral fellowship and S. Y.-V. to the Xunta de Galicia for a postdoctoral grant (Plan I2C).

We report the dielectric response of Ca2?xPrxMnO4 (x = 0 and 0.25). Specifically, their intrinsic dielectric constants are calculated by impedance spectroscopy from the values of the obtained bulk capacitances. For Ca2MnO4, that does not show charge-order, the measured intrinsic dielectric constant is 14. The Pr doping induces charge-order in the system, and also a noteworthy increase in , that reaches a value of ~220 for x = 0.25, unusual in these kind of oxides. This result provides a new link between both phenomena.

The dielectric properties of mixed-oxide CaMn7O12 are reported. This compound exhibits a high dielectric constant at room temperature (er >1 0 4 ), for frequencies up to 10 4 Hz, values that make it very attractive for potential applications provided that its rather high losses can be minimized. Complex plane analysis of the obtained data reveal an important extrinsic contribution to these high er values; and also that the

Polycrystalline samples of the charge ordered mixed oxide LaMn0.5Co0.5O3−δ (TCO = 400 K) have been prepared by the nitrate decomposition method. These samples are biphasic, according to XRPD, and except one, oxygen defficient (δ ≈ 0.04-0.05). The study of the dielectric properties of these samples reveal that LaMn0.5Co0.5O3−δ displays a high dielectric constant, specially at room temperature and low frequencies. This e′r is seen to be strongly dependent on the particle size and not so much on the oxygen defficiency and the best properties are found in the sample with biggest particle size (ϕ = 7 μm) for which e′r (300 K) ≈ 105 up to 2x104 Hz. Analysis of the role of the grain size and the electrode contacts on the obtained data reveal that this mixed oxide has an intrinsic dielectric constant that is rather high for this type of compounds (e′r,∞ ≈ 30) and that is further enhanced by extrinsic Maxwell-Wagner effects. We relate such enhanced intrinsic dielectric constant to the electronic process of charge ordering present in this material below 400 K.

In this work we have prepared, by a sol-gel method, LiCo 1-x M x O 2 compounds (M= Ni, Al and Mg), in order to study the doping effect in their electrochemical behaviour as cathodes in lithium-batteries. We have studied the influence of the synthesis conditions (using various chelating agents for the formation of the gel) on their morphologic, structural and electrochemical properties. We have obtained monophasic materials: LiCo 1-x Ni x O 2 (0≤x≤0.8), LiCo 1-x Mg x O 2 (0≤x≤0.05), LiCo 1-x Al x O 2 (0≤x≤0.3) and LiCo 0.5 Ni 0.5-x Al x O 2 (0≤x≤0.3). In general, the samples obtained with succinic acid have better ordered lithium layers than malic samples.The capacity of the Li//LiCo 1-x M x O 2 batteries decrease upon doping. However, more stable charge-discharge cycling performances have been obtained as compared to those displayed by the native oxides. In LiCo 1-x Mg x O 2 , small amounts of MgO appear as secondary phases for 0.05

We have prepared polycrystalline, single-phase Nd1−xSrxCoO3 materials (0≤x≤0.40) using the nitrate decomposition method and we have studied how their structural, magnetic and transport properties change upon Sr2+ doping. In this context we find that these series of compounds crystallize in GdFeO3-type perovskite structures whose cell volume increases as x gets higher. From the magnetic point of view, this doping makes the materials evolve towards a ferromagnetic behavior as x increases, so that for x>0.20 the samples are already ferromagnetic below a Tc∼225 K. Also, their electrical conductivity progressively increases with x. Nevertheless the materials remain semiconducting for x≤0.30 and only the sample with x=0.40 displays a M–I transition as a function of temperature (TMI∼160 K).

[Abstract] Lithiated metal oxides LiCo1−yNiyO2 were synthesized by a sol–gel method using succinic acid as chelating agent. Microcrystalline materials were formed by calcination in oxygen at 800°C. The physicochemical properties of the powders (crystallinity, lattice constants, size grain) has been investigated in the compositional range 0≤y≤1. Structural studies show that a layered single phase was obtained. The local cationic environment has been studied by Raman and FTIR spectroscopy. The changes in the vibrational spectra are well related to those observed by X-ray diffraction. It is shown that the lithium predominant layers are preserved in the entire range of substitution. Pelletized LiCo1−yNiyO2 powders (0.2≤y≤1.0) were tested in Li//LiCo1−yNiyO2 cells by galvanostatic titration. These cells have an initial capacity of 140 mAh/g in the voltage range 2.8–4.2 V and show attractive charge–discharge profiles upon cycling. Spanish and French Foreign Office; PAI Picasso 00717TC Spanish and French Foreign Office; HF1999-0101

We have synthesized LiNi1−yCoyO2 powders by a sol-gel method using malic acid as a chelating agent. The dependence of physico-chemical properties of the powders (crystallinity, lattice constants, grain size) has been investigated by changing the malic acid quantity and the calcination temperature for the different LiNi1−yCoyO2 oxides in the composition range 0 ≤ y ≤1. Structural studies show that a layered single phase was obtained for the y values 0.2 ≤ y ≤ 1.0. The local cationic environment has been studied by Raman and FTIR spectroscopy. Using acid-assisted LiNi1−yCoyO2 powders (with compositions y=0.8 and y=0.6) calcined at 800 °C, Li//LiNi1−yCoyO2 cells were assembled and tested by galvanostatic titration. These cells had an initial capacity of 140 mAh/g in the voltage range 2.8-4.2 V and showed attractive charge-discharge profiles upon cycling.

We have used three soft-chemistry methods for the efficient preparation of Ln1−xSrxCoO3 samples, adapting the combustion and the liquid-mix methods for the synthesis of the Ln = La and Gd compounds, respectively, and the preparation of Nd1−xSrxCoO3 by the nitrate decomposition method. We report the magnetic and electrical properties of these relatively small particle-size materials, specially in the case of the Ln = La and Ln = Nd series (d≈0.2 µm and 0.5 µm, respectively), and we compare them to those displayed by the corresponding compounds prepared at higher temperatures. The compounds here obtained are ferromagnetic for x≥0.15 when Ln = La and for x≥0.20 when Ln = Nd and Gd. Their resistivity decreases as the doping degree increases. And, very interestingly, for compositions 0.20

Magnetic and transport measurements on the system La{sub 1-x}Sr{sub x} CoO{sub 3-{delta}}(0 < x {le} 0.50, {delta} = 0 for 0 {le} x < 0.30, and {delta} (x) {le} 0.06 for 0.30 {le} x {le} 0.50) have led to a phase diagram for this system. Upon Sr doping, the material segregates into hole-rich, metallic ferromagnetic regions and a hole-poor matrix similar to LaCoO{sub 3}. The Co ions of the ferromagnetic phase are in intermediate-spin configurations; the hole-poor matrix experiences a thermally induced low-spin to high-spin transition. For low Sr doping (x < 0.20), the hole-rich regions are isolated from one another and show superparamagnetic behavior below T{sub c}{approx}240 K; longrange magnetic order via frustrated intercluster interactions occurs below a superparamagnetic freezing temperature T{sub g} that increases with x. At x = 0.20, the coupling between the intermediate-spin, metallic ferromagnetic clusters within an interpenetrating matrix reaches a magnetic percolation threshold that orders the clusters ferromagnetically below T{sub c}{approx} 250 K. However, the electrical conduction in the ferromagnetic regions is modulated by the matrix, which has a spin state that varies with temperature. This causes a reentrant semiconductive behavior in the samples with 0.20 {le} x {le} 0.25. Metallic ferromagnetic behavior ismore » found for 0.30 {le} x {le} 0.50 even though the presence of an interpenetrating hole-poor matrix persists to x = 0.50. A ferromagnetic fraction less than unity leads to peculiar magnetic properties that have been attributed in the literature to a magnetic {open_quotes}cluster glass.{close_quotes}« less

We report that the hybrid organic-inorganic compound [(CH(3))(2)NH(2)][Mg(HCOO)(3)] shows a marked dielectric transition around T(t) ∼ 270 K, associated to a structural phase transition from SG R3[combining macron]c (centrosymmetric) to Cc (non-centrosymmetric). This is the highest T(t) reported so far for a perovskite-like formate that is thus a promising candidate to display electric order very close to room temperature.

This is the accepted manuscript of the following article: Yáñez-Vilar, S., Sánchez-Andújar, M., Gómez-Aguirre, C., Mira, J., Señarís-Rodríguez, M., & Castro-García, S. (2009). A simple solvothermal synthesis of MFe2O4 (M=Mn, Co and Ni) nanoparticles. Journal Of Solid State Chemistry, 182(10), 2685-2690. doi: 10.1016/j.jssc.2009.07.028 Nanoparticles of MFe2O4 (M=Mn, Co and Ni), with diameters ranging from 5 to 10 nm, have been obtained through a solvothermal method. In this synthesis, an alcohol (benzyl alcohol or hexanol) is used as both a solvent and a ligand; it is not necessary, therefore, to add a surfactant, simplifying the preparation of the dispersed particles. We have studied the influence of the synthetic conditions (temperature, time of synthesis and nature of solvent) on the quality of the obtained ferrites and on their particle size. In this last aspect, we have to highlight that the solvent plays an important role on the particle size, obtaining the smallest diameters when hexanol was used as a solvent. In addition, the magnetic properties of the obtained compounds have been studied at room temperature (RT). These compounds show a superparamagnetic behaviour, as was expected for single domain nanoparticles, and good magnetization values. The maxima magnetization values of the MFe2O4 samples are quite high for such small nanoparticles; this is closely related to the high crystallinity of the particles obtained by the solvothermal method The authors are grateful for financial support from the MEC of Spain (Project CSD2006-00012 of Consolider-Ingenio 2010 Programme and FPI fellowship to S. Yáñez-Vilar), from the Xunta de Galicia (Project PGIDIT06PXIB103298PR, Rede Galega de Nanomedicina and Parga Pondal Programme) and from the EU (FEDER) SI

HREM has been used to study the process induced by the reaction of the HTSC YBa{sub 2}Cu{sub 3}O{sub 7{minus}y} (commonly referred to as '123') with the lithiating agent n-BuLi. High resolution electron micrographs reveal that this reaction promotes, at room temperature, irreversible microstructural modifications into the '123' structure leading to a rather heterogeneous product. In this respect, both '247' (Y{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15{minus}z}) and the '124' (YBa{sub 2}Cu{sub 4}O{sub 8}) structures appear as either extended defects within the '123' matrix or disordered intergrowths. A structural model is proposed to justify the high lithium conductivity displayed by these materials.

[Abstract] The Pr0.79Na0.21MnO3 perovskite has been prepared in polycrystalline form by a ceramic method. We have carried out its structural characterization by synchrotron X-ray powder diffraction (SXRPD) at room temperature and at 150 K (T

We report the structure and microstructure of the Ruddlesden-Popper (RP) series n=2 Gd2−2xSr1+2xCo2O7 (x = 0 and 0.10). X-ray powder diffraction, electron diffraction and HRTEM indicate that these compounds have a tetragonal structure (space group: P42/mnm) with cell parameters a ≈ 5.3749A c ≈ 19.3591A, in which the [CoO6] octahedra are distorted and tilted. Also, very interestingly, according to the obtained results these compounds presents A-site cation ordering where the divalent and bigger Sr2+ cation selectively prefers the 12-coordinated P site while the smaller and trivalent Gd3+ cation prefers the 9-coordinated R site. From the electrical point of view these materials are semiconducting and their resistivitiy decreases upon doping. In addition, the highest doped sample presents a small magnetoresistive effect MRmax = −3.2 % under Hmax = 50 kOe at T = 55 K.

We have prepared LiCo1−yAlyO2 and LiNi0.5−yAlyCo0.5O2 (0≤y≤0.3) powder samples by a low temperature sol–gel method using succinic acid as chelating agent. We have studied the details of their crystallographic and local structure by X-ray diffraction (XRD) and FTIR spectroscopy, respectively; we have analyzed their chemical composition by ICP and obtained information about the morphology of the polycrystalline particles by SEM. Also, we have studied the electrochemical performance of the as-prepared materials in the LiLiNi0.5−yAlyCo0.5O2 cells cycled in the potential range 2.5–4.2 V finding that the overall capacity of the oxides has been reduced due to the metal substitution. For example, at 4.2 V cut-off, the charge capacity of the LiLiNi0.35Al0.15Co0.5O2 cell is ca. 115 mA h/g. However, more stable charge–discharge cycling performances have been obtained as compared to those displayed by the native oxides. Finally, we have characterized the kinetics of Li-diffusion by the galvanostatic intermittent titration technique and, according to our results, Al substitution provides an increase in the chemical diffusion coefficients of Li ions in the LiNi0.5−yAlyCo0.5O2 matrix. Spanish and French Foreing Office; PAI Picasso 00717TC Spanish and French Foreing Office; HF 1999-0101