Journal ArticleDOI
The Synthesis, Properties, and Applications of Columbite Niobates (M2+Nb2O6): A Critical Review
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The binary niobate ceramics, with the formula M 2+ Nb 2 O 6 where M 2 + = Ca, Mg, or a transition metal (TM), have the orthorhombic columbite structure as discussed by the authors.Abstract:
The binary niobate ceramics, with the formula M 2+ Nb 2 O 6 where M 2+ = Ca, Mg, or a transition metal (TM), have the orthorhombic columbite structure. The best-known members of this group are zinc niobate (ZnNb 2 O 6 ) and magnesium niobate (MgNb 2 O 6 ), but Ca, Co, Ni, Mn, Cu, Cd, and Fe 2 + cations can also be included in the columbite structure. The TM columbite niobates have been found to sinter at temperatures of 1100°-1200°C, much lower than the complex perovskites, and this can be lowered even more when Cu 2+ is used. The best columbite niobates have Q x f values similar to those of BaZn 0.33 Nb 0.67 O 3 , and all have e r between 17 and 25 and negative τ f values of < -80 ppm/°C. There is a growing interest in the columbites as microwave dielectric ceramics, due to their lower processing temperatures, less complicated processing due to the simple chemistry of the binary compounds, and the lower cost of niobium compared with tantalum, and with incorporation of Cu 2+ they are approaching low-temperature cofired ceramics (LTCC) temperatures. They have also been investigated combined with other dielectric ceramics (to compensate for the negative τ f values), and with additives to lower sintering for LTCC. Furthermore, MgNb 2 Ο 6 is in wide use as a precursor to synthesize single phase PMN (Pb(Mg 1/3 Nb 2/ 3 )O 3 ) in the "columbite" process, and NiNb 2 O 6 is being increasingly investigated as a catalyst for splitting water and organic compounds. CoNb 2 O 6 and other columbites have interesting magnetic properties, and CaNb 2 O 6 and CdNb 2 O 6 have useful optical properties. This review covers the various means of synthesis of these ceramics, and the effects of processing upon structural, physical, electronic, and optical properties. This review will concentrate on the dielectric properties and applications, as this is the greatest area of interest, but will also cover other properties and applications of these ceramics. All available reported microwave dielectric data for columbites is compiled, compared, and assessed.read more
Citations
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Journal ArticleDOI
Niobium oxides and niobates physical properties: Review and prospects
TL;DR: In this paper, a short review on different types of niobates, namely columbite and rare earth, and the relation of the properties of these materials with niobium oxides is presented.
Journal Article
Dielectric Characteristics of Several Complex Oxide Ceramics at Microwave Frequencies : F: Ferroelectric Materials
TL;DR: In this paper, the dielectric properties of several complex-oxide compounds have been investigated for microwave resonator materials, including those with rutile-like crystal structures and complex-oxides related to TiO2.
Journal ArticleDOI
Novel Series of Low‐Firing Microwave Dielectric Ceramics: Ca5A4(VO4)6 (A2+ = Mg, Zn)
TL;DR: Using a conventional solid-state reaction Ca5A4(VO4)6 (A2+ ǫ = Mg, Zn) was prepared and their microwave dielectric properties were investigated for the first time as discussed by the authors.
Journal ArticleDOI
Insight into pathways of methylene blue degradation with H 2 O 2 over mono and bimetallic Nb, Zn oxides
Lukasz Wolski,Maria Ziolek +1 more
TL;DR: In this article, the influence of surface properties of metal oxides on the type of reactive oxygen species (ROS) formed in contact with hydrogen peroxide, and to determine the effect of zinc addition to niobium pentoxide and its activity in methylene blue degradation was investigated.
Journal ArticleDOI
An Insight into Artificial Leaves for Sustainable Energy Inspired by Natural Photosynthesis
Han Zhou,Tongxiang Fan,Di Zhang +2 more
TL;DR: The development of green sustainable energy to control our carbon-based energy addiction and to reduce atmospheric CO2 emissions is one of the most urgent issues regarding the continued existence of man on planet earth as discussed by the authors.
References
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Journal ArticleDOI
Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
TL;DR: The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations as mentioned in this paper.
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Ba(Zn1/3Ta2/3)O3 Ceramics with Low Dielectric Loss at Microwave Frequencies
TL;DR: In this article, the dielectric properties at microwave frequencies of Ba(Zn1/3Ta2/3)O3 ceramics prepared by sintering were investigated.
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Microwave Dielectric Loss of Titanium Oxide
TL;DR: The dielectric loss (tan δ) of titanium dioxide (TiO2) disks has been measured at a frequency of 3 GHz in this article, and the tan δ for all the high-Q doped TiO2 polycrystalline samples smoothly decrease to ∼5 × 10−6 (Q∼ 200 000) at 15 K, comparable to that of single crystals.
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Improved High-Q Dielectric Resonator with Complex Perovskite Structure
TL;DR: In this paper, a perovskite pseudocell and hexagonal superstructure were constructed for the dielectric resonator of the Ba(Ni,Ta)O3-BaZrO3 system.