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.

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.

Application of the Potentiometric Stripping Analysis with Constant Current for the Determination of Lithium Ions Using a Spinel-Type Manganese (IV) Oxide-Modified Carbon Paste Electrode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of the potentiometric response of the doped spinel Li1.05Al0.02Mn1.98O4 for the optimization of a selective lithium ion sensor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ab initio study and NMR analysis of the complexion of citric acid with ion lithium

Quantum mechanics calculations at the ab initio HF/3-21G* level were carried out with Nuclear Magnetic Resonance (NMR) measurements to characterize citric acid and lithium interactions. The results indicate the formation of a tridentate organometallic compound with one lithium and one citric acid molecule and a tridentate and bidentate compound of two lithium atoms and one citric acid molecule. The results are in agreement with the experimental and theoretical data. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Influence of degradation on the electrical conduction process in ZnO and SnO2-based varistors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Single-phase high power-factor boost ZCS pre-regulator operating in critical conduction mode

This paper presents a new single-phase interleaved high power factor boost pre-regulator operating in critical conduction mode, where the switches and boost diode performing zero-current commutations during its turn-off, eliminating the disadvantages related to the reverse recovery losses and electromagnetic interference problems of the boost diode, when operating in the continuous conduction mode. The interleaving technique is applied in the power cell, providing a significant input current ripple reduction in comparison to discontinuous mode of operation, due to its input current continuous conduction operation. This paper presents a complete modeling for the converter operating in critical conduction mode, resulting in an improved design procedure for interleaved techniques with high input power factor, a complete design procedure, and main simulation results from a design example with two interleaved cells rated at 1kW, 400V output voltage and 220V rms input voltage.

Use of lithium niobate detector for measuring X-ray intensity in mammographic range

A detector system that can measure X-ray intensity in the mammographic range of 22 to 36 kVp (equivalent photon energies ofthe beam between 11 and 15 keV) is presented. It consists of a lithium mobate detector and a high-sensitivity current-to-voltage converter.

Evidence of distinct phase transformations in lithium phosphate glass Li2O-P2O5

The purpose of this work is to study the Li2O-P2O5 glass using the differential scanning calorimetry (DSC) and x-ray diffraction (XRD) techniques to understand the crystallization process in this glass matrix. To study the glass by DSC, screened samples with different particle sizes to resolve the crystallization peaks were used. Both crystallization peaks were attributed to Li6P6O18 and LiPO3 phases. This evidence was corroborated by XRD analysis on glasses annealed at different temperatures in order to crystallize these phases.

MOTOR NERVE CONDUCTION and REPETITIVE NERVE STIMULATION IN CAPTIVE RING-TAILED COATI (NASUA NASUA)

There are few electrophysiologic studies in wild animals. The aim of this study was to determine normal data for motor nerve conduction studies and repetitive stimulation in sciatic-tibial and ulnar nerves in clinically normal captive coati. Eight adult ring-tailed coatis (Nasua nasua), two females and six males weighing 68 kg, were used. Average nerve conduction velocity was 70.81 m/sec (standard deviation [SD] = 3.98) and 56.93 m/sec (SD = 4.31) for the sciatic-tibial and ulnar nerves, respectively. Repetitive stimulation responses demonstrated minimal variations of the area of the compound muscle action potentials at low (3 Hz) and high (20 Hz) frequencies. The maximal obtained decremental area response was 8%. These normal data of conduction studies may be used in assessing abnormalities for clinical diagnosis. In addition, the obtained normal repetitive stimulation data were similar to dogs and humans and may be used for post- and presynaptic disturbances of the neuromuscular transmission in coatis.

Effect of lithium additive on the microstructure and electrical responses of 0.9PMN-0.1PT ceramics

Structural effects of lithium additive on 0.9PMN-0.1PT powders prepared by Ti-modified columbite route were studied. The substitution of Li+ ions for Mg2+ ions in the B-site sub-lattice of 0.9PMN-0.1PT perovskite structure was explained in terms of lead and oxygen vacancies generation originated as consequence of the ionic compensation of negatively charged Li'(Mg) sites. The rise in mass transport as consequence of the increasing of Pb2+ and O2- vacancies produces more agglomerated particles during the powder synthesis and changes the mechanical characteristics between grain and grain boundary of sintered ceramic. The relation between K-m and T-m values, the difference between ionic radii of B cation and the molar volume were used to explain the changes in the relaxor behavior and diffusiveness of phase transition as function of lithium doping, which are corroborated by the results obtained through the ferroelectric characterization.

A homovalent doping in PMN ceramics by using lithium and scandium cations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Powder X-ray characterization of lithium thiazoildine-4-carboxylate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

ac conductivity and conduction mechanism of NaNbO3 semiconductor antiferroelectric ceramic: A relaxational approach at high temperature

The electric properties of the sodium niobate perovskite ceramic were investigated by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz and from room temperature up to 1073 K, in a thermal cycle. Both capacitance and conductivity exhibit an anomaly at around 600 K as a function of the temperature and frequency. The electric conductivity as a function of angular frequency sigma(omega) follows the relation sigma(omega)=Aomega(s). The values of the exponent s lie in the range 0.15less than or equal tosless than or equal to0.44. These results were discussed considering the conduction mechanism as being a type of polaron hopping. (C) 2003 American Institute of Physics.