Synthesis and transport properties ofSrxNbO3

Abstract

Polycrystalline samples of Sr NbO, (0.75~x~0.90) have been successfully synthesized by a solidstate reaction technique using TiO as a reducing agent. Powder x-ray-diffraction analysis indicated that the samples with x 0.80 were single phase of the cubic perovskite structure. Electrical resistivity of each sample exhibited metallic behavior at temperatures below 300 K. For the samples with x &0.90, the magnetic susceptibility was nearly temperature independent (Pauli paramagnetic), while the sample with x =0.90 showed a Curie-Weiss behavior. Since the thermoelectric power coefficient (S) was found to be negative for all the samples in the temperature range between 10 and 300 K, the dominant charge carriers in Sr Nb03 (0.75~x~0.90) were thought to be electrons. On the contrary, the nonlinear temperature dependence of S indicated that electrons in Sr"Nb03 were not simply metallic but rather similar to those in amorphous metals.

An investigation of crystal structure, surface area and surface chemistry of strontium niobate and their influence on photocatalytic performance

“…25 In our previous work1, it has been shown that strontium niobate has successfully achieved the water splitting half-reaction of H 2 production under visible light irradiation with oxalic acid as a sacrificial reagent, as well as the photoxidative degradation of methylene blue and oxygen evolution from water with Ag + as 30 sacrificial reagent. In addition, its conductivity was measured equal to 3x10 3 Scm -1 for x= 0.2 and it was found to decrease slightly while the temperature increased, in agreement with what has already been reported in literature [26][27][28] . The temperature coefficient of resistance was calculated to be α t = 2.05 x 10-4 K -1 .…”

“…Cubic symmetry (space group P m-3m) has been reported when the occupancy of Sr lies between (1-x)= 0.75 and 0.9 27,28 ; while distorted structures with a higher Sr occupancy have been found at room temperatures with decreased symmetries 26,31 . More specifically, the material exhibits a cubic phase until around x=0.08 and from that point on, the NbO 6 octahedra reorientate and the structure adopts the less symmetric form of orthorhombic phase 26,29,[31][32][33] .…”

“…The challenges are 5 the reaction conditions as well as the choice of precursors. Previous methods using SrO as a precursor in a vacuous quartz condition have many drawbacks, not only because SrO is sensitive towards CO 2 and H 2 O but also, because it may react with quartz to form stable silicates 27,34 . …”

“…Some impurity peaks were occasionally present in the patterns but they were quite small. The refined unit cell parameters are 15 listed in 27,28 , although values do vary probably due to differing microstructures of the sintered pellets. From SEM images (Fig.…”

Crystal Structure Refinement of MgNb2O6Columbite from Neutron Powder Diffraction Data and Study of the Ternary System MgO–Nb2O5–NbO, with Evidence of Formation of New Reduced Pseudobrookite Mg5−xNb4+xO15−δ(1.14≤x≤1.60) Phases

“…In these superconducting phases the formal oxidation state of niobium is lower than #5. Also, mixed oxides in which Nb presents an oxidation state between #4 and #5, such as Sr V NbO (0.75(x( 0.90) and BaNbO , have also been investigated, although no superconducting behavior was reported (3,4).…”