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The role of lithium excess and Mn doping on lithium titanium phosphate properties is studied by structural (X-ray and neutron diffraction) and spectroscopic (electron paramagnetic resonance and impedance) techniques. The dopant cation is present with 2+, 3+, and 4+ oxidation states in both the lithium and titanium sublattices: Mn2+ is preferentially located on Li sites and Mn4+ on Ti ones, and Mn3+ can occupy both the sites. The refinement of neutron diffraction patterns allowed us to identify the 18e crystallographic site as the preferred location of the excess Li ions. Cationic distribution and valence state are mainly related to sol–gel or solid-state synthesis routes. Consequently, the complex behavior of the bulk conductivity can be explained by the presence of Mn on the Li site and the amount of Li excess, while the effect of the sintering degree is comparable in all the samples as revealed by scanning electron microscopy.

Structural, microstructural, and spectroscopic properties of Ba6Zr2Ta8O30 (BZT) and Ba6Zr1.94M0.06Ta8O30 (M = Ni, Co, Fe, Mn, Cr) related doped compounds are reported. The distribution of Zr, Ta, and M dopant ions on the cationic sites and the M valence states are discussed on the basis of the results obtained by the application of the Rietveld method on X-ray powder diffraction (XRPD) patterns and by electron paramagnetic resonance. The micro-Raman spectra of pure and doped BZT, reported and discussed for the first time, confirm the capability of the lattice to host transition cations in a glasslike matrix. The particle size effects of the samples are investigated by analyzing XRPD line broadening and scanning electron microscopy observations. Comparisons with the isostructural pure and doped Ba6Ti2Nb8O30 compounds are also reported.

Pure and doped Ba 6 Ti 2 Nb 8 O 30 (BTN), obtained by substituting M = Cr, Mn, or Fe on the Ti site (Ba 6 Ti 2-x M x Nb 8 O 30 , x = 0.06 and 0.18) and Y and Fe on the Ba and Ti sites, respectively (Ba 6-x Y x Ti 2-x Fe x Nb 8 O 30 , x = 0.18), are synthesized. The influence of cation doping on the local structure, the cation oxidation state, and the possible defect formation able to maintain the charge neutrality are investigated by spectroscopic (electron paramagnetic resonance (EPR) and micro-Raman), structural (X-ray powder diffraction) and transport (impedance spectroscopy, thermoelectric power) measurements, in the temperature range of 300-1200 K in air and N 2 flow. Starting from the valence state of the doping ions (Fe 3+ , Cr 3+ , and Mn 2+ ), determined by EPR, and from thermoelectric power measurements, evidencing a negative charge transport, different charge-compensating defect equilibria, based on the creation of positive electron holes or oxygen vacancies and electrons, are discussed to interpret the conductivity results.

Ga-doped Li−Mn-spinels Li1.02GaxMn1.98-xO4 with 0.00 ≤ x ≤ 0.20 are investigated to verify the lattice capability to allocate the Ga3+ ions on both tetrahedral and octahedral sites and to determine the lowest amount of dopant that prevents the occurrence of the Jahn−Teller (J−T) transition observed near room temperature in LiMn2O4. XRPD, NMR, and EPR spectra and static magnetic susceptibility and conductivity data are related to the site occupancy, the Mn valence state and the homogeneous distribution of the dopant. The electronic and magnetic features of the spinel framework are strongly dependent on substitution in its cationic sublattice: dopant amounts as low as 1% significantly modify the temperature of the conductivity drop associated with the J−T distortion. Ga3+ ions substitute chiefly in the octahedral sites, Mn4+ ions occupy regular and distorted octahedral sites and, at the same time, the value of lattice parameter remains unchanged. Mn2+ ions are present in the tetrahedral site and Li+ increa...