Phase-field Determination of NaSICON Materials in the Quaternary System Na2 O-P2 O5 -SiO2 -ZrO2 : The Series Na3 Zr3-x Si2 Px O11.5+x/2.

Two types of solid electrolytes have reached technological relevance in the field of sodium batteries: ß/ß"-aluminas and NaSICON-type materials. Today, significant attention is paid to room-temperature stationary electricity storage technologies and all-solid-state Na batteries used in combination with these solid electrolytes are an emerging research field besides sodium-ion batteries. In comparison, NaSICON materials can be processed at lower sintering temperatures than the ß/ß"-aluminas and have a similarly attractive ionic conductivity. Since Na2 O-SiO2 -ZrO2 -P2 O5 ceramics offer wider compositional variability, the series Na3 Zr3-x Si2 Px O11.5+x/2 with seven compositions (0≤x≤3) was selected from the quasi-quaternary phase diagram in order to identify the predominant stability region of NaSICON within this series and to explore the full potential of such materials, including the original NaSICON composition of Na3 Zr2 Si2 POl2 as a reference. Several characterization techniques were used for the purpose of better understanding the relationships between processing and properties of the ceramics. X-ray diffraction analysis revealed that the phase region of NaSICON materials is larger than expected. Moreover, new ceramic NaSICON materials were discovered in the system crystallizing with a monoclinic NaSICON structure (space group C2/c). Impedance spectroscopy was utilized to investigate the ionic conductivity, giving clear evidence for a dependence on crystal symmetry. The monoclinic NaSICON structure showed the highest ionic conductivity with an optimum ionic conductivity of 1.22×10-3 at 25 °C for the composition Na3 Zr2 Si2 PO12 . As the degree of P5+ content increases, the total ionic conductivity is initially enhanced until x=1 and then decreases again. Simultaneously, the increasing amount of phosphorus leads a decrease in the sintering temperatures for all samples, which was confirmed by dilatometry measurements. The thermal and microstructural properties of the prepared samples are also evaluated and discussed.

Fast Na ion transport triggered by rapid ion exchange on local length scales.

The realization of green and economically friendly energy storage systems needs materials with outstanding properties. Future batteries based on Na as an abundant element take advantage of non-flammable ceramic electrolytes with very high conductivities. Na3Zr2(SiO4)2PO4-type superionic conductors are expected to pave the way for inherently safe and sustainable all-solid-state batteries. So far, only little information has been extracted from spectroscopic measurements to clarify the origins of fast ionic hopping on the atomic length scale. Here we combined broadband conductivity spectroscopy and nuclear magnetic resonance (NMR) relaxation to study Na ion dynamics from the µm to the angstrom length scale. Spin-lattice relaxation NMR revealed a very fast Na ion exchange process in Na3.4Sc0.4Zr1.6(SiO4)2PO4 that is characterized by an unprecedentedly high self-diffusion coefficient of 9 × 10-12 m2s-1 at -10 °C. Thus, well below ambient temperature the Na ions have access to elementary diffusion processes with a mean residence time τNMR of only 2 ns. The underlying asymmetric diffusion-induced NMR rate peak and the corresponding conductivity isotherms measured in the MHz range reveal correlated ionic motion. Obviously, local but extremely rapid Na+ jumps, involving especially the transition sites in Sc-NZSP, trigger long-range ion transport and push ionic conductivity up to 2 mS/cm at room temperature.

Single-dose pharmacokinetics of labetalol in healthy young men.

Single doses of labetalol (200 mg i.v. over 5 min, 200 and 400 mg orally) were given to five healthy men on three different occasions. Plasma levels were followed for up to 25 h and blood pressure for 5 h. The elimination half-life was 1.6 to 8.5 h for the first 8 h. The oral bioavailability ranged from 4 to 23%. All doses induced a significant fall in systolic blood pressure at 2 h, the peak effect occurring at 30--120 (mean 63-72) min. After intravenous administration the peak supine blood-pressure fall was significant for both systolic and diastolic blood pressure and occurred 16 min after administration.

Validation of methods for determination of urinary estriol during pregnancy using mass fragmentography.

A specific and accurate method for determination of urinary estriol during pregnancy is described. After acid hydrolysis of 1 ml urine, a fixed amount of [2,4-2H2] estriol (usually 15 mug) is added and the mixture is extracted with diethyl ether. The extracted estriol is converted into the tri-trimethylsily derivative and the amount of unlabeled estriol is determined from the ratio between the recordings at m/e 504 and m/e 506 obtained after analysis with a gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions used correspond to the molecular peak in the mass spectrum of unlabeled and (2,4-2H2)-labeled tri-trimethylsilyl derivative, respectively. The relative standard deviation of the method was about 6%. The method was compared with a photometric method using the Kober reaction and the gas liquid chromatographic method used in routine analysis. There was a good correlation in both cases and the regression coefficient was 1.5 and 1.3, respectively.