Influence of Mg on the structural and optical properties of LiNbO3 thin films grown by polymeric precursor method

A polymeric precursor solution was used to deposit pure and Mg doped LiNbO3 thin films on sapphire substrates by spin-coating. The effects of magnesium addition on crystallinity, morphology and optical properties of the annealed films were investigated. X-ray diffraction patterns indicate the oriented growth of the films. Phi-scan diffraction evidenced the epitaxial growth with two in-plane variants. AFM studies show that the films are very homogeneous, dense and present smooth surfaces. The refractive index and optical losses obtained by the prism coupling method were influenced by the magnesium addition.

Phonons in binary BCC lithium-sodium alloys

The dispersion relations along the principal symmetry directions in BCC lithium-sodium alloys are calculated using second-order perturbation theory. The local modified Hoshino-Youngmodel potential was used for the lithium and the local Harrison model potential for sodium. The phonon density of states, the root mean square displacements and (Θ-T) curves are also calculated. In the absence of experimental data, just the theoretical predictions are presented here.

Lithium-lanthanum double chromates

Synthesis and crystallographic data are reported for low and high temperature forms of LiLa(CrO4)2. The compounds are closely related to lamellar rare earth phosphates and arsenates of sodium and to RbLu(CrO4)2. Lattice parameters of the orthorhombic (low temperature) and monoclinic (high temperature) forms are given. The low temperature form is moisture sensitive and Li+ ions are easily displaced by protons. Thermal decomposition takes place at 250 °C and results in the formation of LiCrO2, LaCrO4, LaCrO3 and Cr2O3. © 1993.

Lanthanum-lithium-sodium double chromates as ionic conductors

Lanthanum-lithium-sodium double chromates Li1-xNaxLa(CrO4)2 were prepared and analysed by means of admittance spectroscopy. Their a.c. conductivity parameters are correlated with structural details of high and low temperature forms of pure lanthanum-lithium double chromates. Lithium compounds show the lowest conductivity values and the highest activation energy for ion motion, while the sample Li0.5Na0.5La(CrO4)2 exhibits the highest conductivity 10-5 S cm-1 and the lowest activation energy 0.58 eV.

Lithium intercalation into double rare earth chromates

Lithium intercalation into double rare earth chromates was carried out. It was found that the compounds NaxLi1-xLa(CrO4)2 belong to the NaLa(CrO4)2 structural type and may be recommended as fast ionic conductors. At small values of x a third polymorphous modification of LiLa(CrO4)2 can be stabilized. Attempts to intercalate lithium into CsLa(CrO4)2 lead to collapse of the lamellar network with the formation of LaCrO4 and alkaline chromates. Ion exchange Li+/H+ data are consistent with these considerations. © 1994.