13769-43-2Relevant articles and documents
Influence of neodymium doping on dielectric properties of ferroelectric KVO3 and LiVO3
Patil,Patil,Kashid,Chavan
, p. 57 - 62 (1990)
The dielectric properties of pure and doped with different concentrations of Nd2O3 ferroelectric KVO3 and LiVO3, have been studied by using a digital LCR meter VLCR-7 at fixed frequency (1KHz) in the region of their phase transition. The dielectric constant shows a sharp peak at the phase transition in all the compositions. The dielectric constant is found to increase significantly, when dopant concentration is increased up to 0.5 mol % Nd2O3, however decreases for higher concentrations. The Curie temperature of all the samples decreases with increase in Nd concentration.
Ramsey, J. B.,Robinson, A.
, p. 480 - 483 (1930)
Observation of metal-insulator transition in hollandite vanadate, K 2V8O16
Isobe, Masahiko,Koishi, Shigenori,Kouno, Naomi,Yamaura, Jun-Ichi,Yamauchi, Touru,Ueda, Hiroaki,Gotou, Hirotada,Yagi, Takehiko,Ueda, Yutaka
, (2006)
We have synthesized hollandite vanadate, K2V8O 16, by a solid-state reaction under 4 GPa at 1473 K for one hour, and investigated its structural and electromagnetic properties. We found a metal-insulator transition with a two-step jump of resistivity of about three orders at around 170 K. The magnetic susceptibility is reduced to a small value at the transition, suggesting the formation of V4+-V4+ singlet pairs and V3+-V3+ pairs in the low-temperature insulator phase. The transition is of first order accompanied by a structural change from a tetragonal to a monoclinic structure. The low-temperature phase has a superlattice of √2a × √2a × 2c, where a and c denote the parameters of the primitive cell for the simple tetragonal hollandite structure, suggesting a charge ordering of V4+ and V3+. We construct a possible charge order model from the obtained results, in which two kinds of double-chain formed by V3+ and V4+ chains and by single V4+ chains order in a manner that gives a superlattice of √2 × √2 in the a-b plane. The V4+-V4+ and V3+-V3+ pairs are formed in each chain along the c-axis, resulting in a duplication of the c-axis. 2006 The Physical Society of Japan.
KV6O11: A magnetic metal synthesized at high pressure
Kanke, Yasushi
, p. 3764 - 3776 (1999)
An AV6O11-type magnetic metal KV6O11 was discovered by a high-pressure synthesis. It crystallizes in hexagonal P63/mmc at 295 K, whereas in hexagonal P63mc at 154 K. KV6O11 shows three magnetic transitions at 190, 66.8, and 35.1 K. KV6O11 is paramagnetic above 66.8 K. Its inverse magnetic susceptibility is slightly concave upward with respect to temperature above 190 K, but the relationship is significantly concave upward below 190 K. KV6O11 shows uniaxial magnetic anisotropy with an easy axis of magnetization parallel to the [001] direction below 66.8 K. The magnetization shows an anomaly at 35.1 K. The resistivity normal to [001] is of the order of 10-4 Ω cm-1. The resistivity versus temperature shows a positive slope above 190 K, a broad maximum at around 90 K, a linear relationship with a positive slope between 35.1 and 66.8 K, and Fermi-liquid-type behavior below 35.1 K. The paramagnetic state below 190 K is discussed on the basis of two types of spin-gap models. Problems of the models are also pointed out. The saturated magnetization versus temperature shows a hyperbolic relationship. The magnetization cannot be explained by the well-known mean field theory or the spin fluctuation mechanism. 1999 The American Physical Society.
Explorations of new second-order nonlinear optical materials in the potassium vanadyl iodate system
Sun, Chuan-Fu,Hu, Chun-Li,Xu, Xiang,Yang, Bing-Ping,Mao, Jiang-Gao
, p. 5561 - 5572 (2011)
Four new potassium vanadyl iodates based on lone-pair-containing IO 3 and second-order Jahn-Teller distorted VO5 or VO 6 asymmetric units, namely, α-KVO2(IO 3)2(H2O) (Pbca), β-KVO2(IO 3)2(H2O) (P21212 1), K4[(VO)(IO3)5] 2(HIO3)(H2O)2 H2O (P1), and K(VO)2O2(IO3)3 (Ima2) have been successfully synthesized by hydrothermal reactions. α-KVO 2(IO3)2(H2O) and β-KVO 2(IO3)2(H2O) exhibit two different types of 1D [VO2(IO3)2]- anionic chains. Neighboring VO6 octahedra in the α-phase are corner-sharing into a 1D chain with the IO3 groups attached on both sides of the chain in a uni- or bidentate bridging fashion, whereas those of VO5 polyhedra in the β-phase are bridged by IO3 groups into a right-handed helical chain with remaining IO3 groups being grafted unidentately on both sides of the helical chain. The structure of K4[(VO)(IO3)5]2(HIO 3)(H2O)2 H2O contains novel isolated [(VO)(IO3)5]2- units composed of one VO 6 octahedron linked to five IO3 groups and one terminal O2- anion. The structure of K(VO)2O2(IO 3)3 exhibits a 1D [(VO)2O2(IO 3)3]- chain in which neighboring VO6 octahedra are interconnected by both oxo and bridging iodate anions. Most interestingly, three of four compounds are noncentrosymmetric (NCS), and K(VO)2O2(IO3)3 displays a very strong second-harmonic generation response of about 3.6 × KTP, which is phase matchable. It also has high thermal stability, a wide transparent region and moderate hardness as well as an excellent growth habit. Thermal analyses and optical and ferroelectric properties as well as theoretical calculations have also been performed.(Figure Presented)
Investigation of the high temperature reaction of the alkali metal metavanadates MVO3 (M=Na,K) with the lanthanide oxides Ln2O3 (Ln=Nd,Er)
de Waal,Heyns,Range
, p. 1193 - 1199 (1991)
The changes occurring in the dielectric constant of an alkali metal metavanadate after it has been treated at high temperatures with a small percentage of a lanthanide oxide have been ascribed to solid solution formation. Analysis of the products obtained by means of Raman spectroscopy, X-ray powder diffraction, SEM and EDX analysis, however, revealed that a small amount of the lanthanide orthovanadate is formed in the metavanadate mass. The reaction that takes place could be described by the following equation: 2MVO3 + Ln2O3 Δ/→ LnVO4 + M2O. With stoichiometric amounts of the reagents under vacuum conditions full conversion to the lanthanide orthovanadate occurs.
Study of thermal properties of potassium μ-hydroxo-bis(oxo-diperoxovanadate) (V)
Joniakova,Schwendt
, p. 207 - 215 (1993)
The thermal decomposition of K3[OH{VO(O2)2)2]·H2O was studied near dynamic conditions up to 350°C and also isothermally at 150°±3°C in self-generated atmosphere. K4[V2O6/su
Vanadium(V) tartrato complexes: Speciation in the H3O +(OH-)/H2VO4-/(2R,3R)- tartrate system and X-ray crystal structures of Na4[V 4O8(rac-tart)2]·12H2O and (NEt4)4[V4O8((R,R)-tart) 2]·6H2O ...
Schwendt, Peter,Tracey, Alan S.,Tatiersky, Jozef,Galikova, Jana,Zak, Zdirad
, p. 3971 - 3983 (2007)
Full title. 3971-3983 Vanadium(V) tartrato complexes: Speciation in the H3O +(OH-)/H2VO4-/(2R,3R)- tartrate system and X-ray crystal structures of Na4[V 4O8(rac-tart)2]·12H2O and (NEt4)4[V4O8((R,R)-tart) 2]·6H2O (tart = C4H2O64-). A study of the aqueous H3O+(OH-)/H 2VO4-/(2R,3r)-tartrate system has been performed at 273 K in a 1.0 mol/L Na+(Cl-) ionic medium using 51V NMR spectroscopy. In this relatively complicated system, more than 12 different species were observed. Ligand concentration, vanadate concentration, and pH variation studies were carried out, particularly for the range of pH 5.8-8.0 and for pH 2.4. Chemical shifts, vanadium-ligand stoichiometry, and also composition and formation constants for some, but not all, species are given. Despite some reduction of vanadium-(V) to vanadium(IV) in an acidic medium at pH ≈2.4, the stoichiometries of the principal species in solution at this pH were determined. Electrospray ionization mass spectra for some solutions were obtained and were in accordance with the conclusions drawn from the speciation studies. A series of crystalline vanadium(V) tartrato complexes M4[V4O8(tart)2]·aq were also prepared and characterized. X-ray diffraction studies of Na 4[V4O8(rac-tart)2]·12H 2O (1) and (NEt4)4[V4O 8((R,R)-tart)2]·6H2O (2) revealed unique tetranuclear [V4O8(tart)2]4- ions for which the {V4O4} rings have boat conformations.
Ag2O/Ag3VO4/Ag4V2O7 heterogeneous photocatalyst prepared by a facile hydrothermal synthesis with enhanced photocatalytic performance under visible light irradiation
Ran, Rong,McEvoy, Joanne Gamage,Zhang, Zisheng
, p. 140 - 150 (2016)
A novel Ag2O/Ag3VO4/Ag4V2O7 photocatalyst was synthesized by adjusting the molar ratio of silver-vanadium (Ag-V) in a facile hydrothermal method to obtain multi-phase Ag2O/Ag3VO4/Ag4V2O7 photocatalyst. The photocatalytic activity of the prepared samples was quantified by the degradation of Rhodamine B (RhB) model organic pollutant under visible light irradiation. Compared to pure Ag3VO4, Ag4V2O7 and P25 TiO2, respectively, the as-synthesized multi-phase Ag2O/Ag3VO4/Ag4V2O7 powders gave rise to a significantly higher photocatalytic activity, achieving up to 99% degradation of RhB in 2 h under visible light. This enhanced photocatalytic performance was attributed to the effect of the multi-phase Ag2O/Ag3VO4/Ag4V2O7 photocatalyst and the surface plasmon resonance (SPR) of the incorporated metallic silver (Ag0) nanoparticles (NPs) generated during the photocatalysis, as evidenced by post-use characterization, resulting in improved visible light absorption and electron-hole (e--h+) separation. A mechanism was proposed for the photocatalytic degradation of RhB on the surface of Ag2O/Ag3VO4/Ag4V2O7.
Investigation of pyroelectric characteristics of Al2O3 doped KVO3 and CsVO3
Rasal,Kashid,Patil,Chavan
, p. 995 - 1000 (1991)
The pyroelectric properties of undoped and aluminium-oxide doped potassium vanadate and cesium vanadate have been studied in the temperature range covering their transition points. The values of pyroelectric current and coefficient of undoped and Al2O3-doped KVO3 and CsVO3 show a sharp peak at their Curie temperature. These Curie temperatures are consistent with those investigated by dielectric-constant measurements and the hysteresis-loop method. The Curie temperatures of KVO3 and CsVO3 doped with Al2O3 decrease with increasing dopant concentrations.
Thermoanalytical study of the solid state reactions in the K2CO3-MxOy systems. Evidence for a kinetic compensation effect
Milic,Colovic,Antonijevic,Gaal
, p. 229 - 238 (2000)
This paper presents the results obtained in the investigation of the reactions of potassium carbonate with some transition metals oxides (TiO2, V2O5, Cr2O3, MnO2, Fe2O3). The reactions were carried out under non-isothermal conditions, and thermogravimetric analysis was used to monitor the transformation degree α. Experimental data indicated that the reaction of potassium carbonate and iron(III) oxide occurs in one stage, whereas the reactions of the oxides of titanium, vanadium, chromium and manganese are more complex, involving two-stage processes. Activation energies and pre-exponential factors were determined for all the processes taking place in the investigated systems. For the second stage of the reaction of K2CO3 with Cr2O3, and V2O5 the obtained values of activation energy were 59.2 and 512 kJ mol-1 respectively. Based on the values of activation energy and pre-exponential factor, the existence of a kinetic compensation effect was postulated for the three homologous series of reactions.
Joniakova, D.,Schwendt, P.,Sivak, M.
, p. 213 - 220 (1991)
K3VO2(SO4)2: Formation conditions, crystal structure, and physicochemical properties
Krasil'nikov,Tyutyunnik,Zubkov,Berger,Perelyaeva,Baklanova
, p. 18 - 25 (2011)
Potassium oxosulfatovanadate(V) K3VO2(SO 4)2 has been obtained by solid-phase synthesis from K 2SO4, K2S2O7, and V 2O5 (2: 1: 1), and
Na1/2Bi1/2VO3 and K1/2Bi1/2VO3: New Lead-Free Tetragonal Perovskites with Moderate c/ a Ratios
Yamamoto, Hajime,Ogata, Takahiro,Patel, Satyanarayan,Koruza, Jurij,R?del, Jürgen,Paul, Atanu,Saha-Dasgupta, Tanusri,Sakai, Yuki,Itoh, Mitsuru,Azuma, Masaki
, p. 6728 - 6736 (2018/10/02)
New lead-free tetragonal perovskites Na1/2Bi1/2VO3 and K1/2Bi1/2VO3 were synthesized under high pressure (6 GPa) and high temperature (1473 K), based on the design of materials optimizing the lone pair effect of the A-site ion and utilizing the Jahn-Teller effect in the B-site V4+. The magnitudes of the c/a ratio and spontaneous polarization, PS, were 1.085 and 108 μC/cm2, respectively (73 μC/cm2 by the point charge model), for Na1/2Bi1/2VO3 and 1.054 and 92 μC/cm2, respectively (56 μC/cm2 by the point charge model), for K1/2Bi1/2VO3, which are comparable to the well-known lead-based ferroelectric PbTiO3. This approach can guide the design of new lead-free ferroelectric and piezoelectric materials.
