High Entropy Oxide Phases with Perovskite Structure

Solid solutions and composites of a mixture of (K0.5Na0.5)NbO3 (KNN) and SrTiO3 (ST) were respectively synthesized by different process routes using a conventional solid state reaction. All starting materials were mixed simultaneously and calcined at 800 oC for 4 h to obtain the solid solutions of KNN-ST. Meanwhile, the composites of KNN-ST were obtained by mixing the synthesized KNN and synthesized ST, respectively. KNN-ST calcined powders were sintered at 1150, 1250 and 1300 oC for 2 h. The calcined powders, in which all starting materials were mixed at once, showed a single-phase pseudo-cubic structure after sintering. On the other hand, the powders with the mixture of KNN and ST had two phases of cubic ST and orthorhombic KNN as composites. The dielectric loss values of all samples decreased as the sintering temperature increased because of increased densification. The dielectric constants of the solid solutions were increased as the sintering temperature increased, however, the dielectric constants of the composites decreased with increasing sintering temperature. It was concluded that, for enhanced dielectric properties, the dielectric materials should be synthesized as solid solutions.

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Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ Ceramics with Ba2+ Substitution at A-Site

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.196 ◽

2007 ◽

Vol 336-338 ◽

pp. 196-198

Author(s):

Dong Xiang Zhou ◽

G. Xiong ◽

Shu Ping Gong ◽

Jun Zhao ◽

M.Z. Hu ◽

...

Keyword(s):

Dielectric Properties ◽

Perovskite Structure ◽

Single Phase ◽

Microwave Dielectric Properties ◽

Bond Valence ◽

Microwave Properties ◽

Microwave Dielectric ◽

Orthorhombic Perovskite ◽

A Site

The microwave properties of (Ca1-xBax)[(Li1/3Nb2/3)0.95Zr0.15]O3+δ(0.0≤x≤0.2, CBLNZ) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x = 0.0 − 0.025. Both the εr and Qf value firstly increased with increasing Ba2+ content, and then began to decrease at x = 0.025. The τf value increased from −9.4 ppm/°C at x=0.0 to 18ppm/°C at x=0.2, which could be explained by the decrease of B-site bond valence in perovskite structure.

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Crystal Structure and Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ Ceramics with Pr3+ Substitution at A-Site

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.181-182.439 ◽

2011 ◽

Vol 181-182 ◽

pp. 439-442

Author(s):

Gang Xiong

Keyword(s):

Crystal Structure ◽

Dielectric Properties ◽

Quality Factor ◽

Perovskite Structure ◽

Single Phase ◽

Microwave Dielectric Properties ◽

Microwave Dielectric ◽

Resonator Frequency ◽

Orthorhombic Perovskite ◽

A Site

Crystal structure and microwave dielectric properties of (Ca1-xPrx) [(Li1/3Nb2/3)0.95Zr0.15]3+δ (0.0≤x≤0.2, CPLNZ) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.08. With an increase of Pr3+ content, the quality factor value firstly increased, and then began to decrease at x=0.06 due to a decrease of the degree of B-site 1:2 ordering. The variation of τf with tolerance factor was discussed. When x=0.06, the optimum microwave dielectric properties: the permittivity is 33.2, the quality factor is 17120 GHz，and the temperature coefficient of resonator frequency is −5.7×10−6/°C.

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Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ Ceramics with Sm3+ Substitution at A-Site

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.698 ◽

2010 ◽

Vol 663-665 ◽

pp. 698-701

Author(s):

Gang Xiong

Keyword(s):

Crystal Structure ◽

Dielectric Properties ◽

Quality Factor ◽

Perovskite Structure ◽

Single Phase ◽

Microwave Dielectric Properties ◽

Microwave Dielectric ◽

Resonator Frequency ◽

Orthorhombic Perovskite ◽

A Site

Crystal structure and microwave dielectric properties of (Ca1-xSmx) [(Li1/3Nb2/3)0.95Zr0.15]3+δ(0.0≤x≤0.2,CSLNZ) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.08. With an increase of Sm3+ content, the quality factor value firstly increased, and then began to decrease at x=0.03 due to a decrease of the degree of B-site 1:2 ordering. The variation of τf with tolerance factor was discussed. When x=0.05, the optimum microwave dielectric properties: the permittivity is 32.4，the quality factor is 16560GHz，and the temperature coefficient of resonator frequency is −6.3×10−6/°C。

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Is Configurational Entropy the Main Stabilizing Term in Rock-Salt Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O High-Entropy Oxide?

10.26434/chemrxiv.14464980 ◽

2021 ◽

Author(s):

Martina Fracchia ◽

Mauro Coduri ◽

Maela Manzoli ◽

Paolo Ghigna ◽

Umberto Anselmi-Tamburini

Keyword(s):

Solid Solution ◽

Rock Salt ◽

Single Phase ◽

Configurational Entropy ◽

Rock Salt Structure ◽

High Entropy ◽

Reversible Transformation ◽

Salt Structure ◽

Cubic Structure

We question the conclusions reported in the paper "Entropy-stabilized Oxides, by C. Rost et al., by looking into the role of configurational entropy as the stabilization of the rock-salt cubic structure of the Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (HEO) solid solution (SS). First, we demonstrate that configurational entropy can be reduced from 1.61R for HEO to 0.5R for a two-member SS, still obtaining a single-phase material if the molar fractions of ZnO and CuO are 0.2. These SSs behave identically as HEO regarding the reversible transformation between a multi- and single-phase states when temperatures are cycled between 800 and 1000 °C. Second, we demonstrate that the different SSs presenting a configurational entropy significantly lower than HEO, are less prone to the cubic to tetragonal structural distortion, suggesting that the configurational entropy has not the central role as stabilizing factor of the rock-salt structure.<br>

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Is Configurational Entropy the Main Stabilizing Term in Rock-Salt Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O High-Entropy Oxide?

10.26434/chemrxiv.14464980.v1 ◽

2021 ◽

Author(s):

Martina Fracchia ◽

Mauro Coduri ◽

Maela Manzoli ◽

Paolo Ghigna ◽

Umberto Anselmi-Tamburini

Keyword(s):

Solid Solution ◽

Rock Salt ◽

Single Phase ◽

Configurational Entropy ◽

Rock Salt Structure ◽

High Entropy ◽

Reversible Transformation ◽

Salt Structure ◽

Cubic Structure

We question the conclusions reported in the paper "Entropy-stabilized Oxides, by C. Rost et al., by looking into the role of configurational entropy as the stabilization of the rock-salt cubic structure of the Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (HEO) solid solution (SS). First, we demonstrate that configurational entropy can be reduced from 1.61R for HEO to 0.5R for a two-member SS, still obtaining a single-phase material if the molar fractions of ZnO and CuO are 0.2. These SSs behave identically as HEO regarding the reversible transformation between a multi- and single-phase states when temperatures are cycled between 800 and 1000 °C. Second, we demonstrate that the different SSs presenting a configurational entropy significantly lower than HEO, are less prone to the cubic to tetragonal structural distortion, suggesting that the configurational entropy has not the central role as stabilizing factor of the rock-salt structure.<br>

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Extremely Polysubstituted Magnetic Material Based on Magnetoplumbite with a Hexagonal Structure: Synthesis, Structure, Properties, Prospects

Nanomaterials ◽

10.3390/nano9040559 ◽

2019 ◽

Vol 9 (4) ◽

pp. 559 ◽

Cited By ~ 7

Author(s):

Denis Vinnik ◽

Vladimir Zhivulin ◽

Evgeny Trofimov ◽

Andrey Starikov ◽

Dmitry Zherebtsov ◽

...

Keyword(s):

Single Phase ◽

Barium Hexaferrite ◽

Synthesis Temperature ◽

Hexagonal Structure ◽

Frequency Range ◽

High Concentration ◽

High Entropy ◽

Structure Synthesis ◽

Parameter Values ◽

Structure Properties

Crystalline high-entropy single-phase products with a magnetoplumbite structure with grains in the μm range were obtained using solid-state sintering. The synthesis temperature was up to 1400 °C. The morphology, chemical composition, crystal structure, magnetic, and electrodynamic properties were studied and compared with pure barium hexaferrite BaFe12O19 matrix. The polysubstituted high-entropy single-phase product contains five doping elements at a high concentration level. According to the EDX data, the new compound has a formula of Ba(Fe6Ga1.25In1.17Ti1.21Cr1.22Co1.15)O19. The calculated cell parameter values were a = 5.9253(5) Å, c = 23.5257(22) Å, and V = 715.32(9) Å3. The increase in the unit cell for the substituted sample was expected due to the different ionic radius of Ti/In/Ga/Cr/Co compared with Fe3+. The electrodynamic measurements were performed. The dielectric and magnetic permeabilities were stable in the frequency range from 2 to 12 GHz. In this frequency range, the dielectric and magnetic losses were −0.2/0.2. Due to these electrodynamic parameters, this material can be used in the design of microwave strip devices.

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Effect of Different Doping on the Structure and Field-Stability of PMNT Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.36 ◽

2007 ◽

Vol 336-338 ◽

pp. 36-38

Author(s):

Xiao Wei Wen ◽

Chu De Feng ◽

Li Dong Chen ◽

Shi Ming Huang

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Perovskite Structure ◽

Single Phase ◽

Secondary Phase ◽

X Ray Diffraction ◽

X Ray ◽

Co Doping ◽

Diffraction Patterns

Effect of co-doping two different elements and incorporating SrBi2Nb2O9 (SBN) on structure and field-stability of dielectric properties in PMNT ceramics were investigated. Single-phase cubic Perovskite structure is more easily obtained by appropriate co- doping of La3+ and Zn2+. X-ray diffraction patterns of PMNT/SBN composite showed that there is no SBN grains in PMNT/SBN as a secondary phase. Co-doping of La3+ and Zn2+ as well as incorporation of SBN markedly increased the field-stability of dielectric constant. The mechanism of improving field-stability was tentatively discussed.

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Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.95Zr0.05]O3−δ−xTiO2 Ceramics

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.181-182.405 ◽

2011 ◽

Vol 181-182 ◽

pp. 405-408

Author(s):

Gang Xiong

Keyword(s):

Crystal Structure ◽

Dielectric Properties ◽

Perovskite Structure ◽

Single Phase ◽

Microwave Dielectric Properties ◽

Microwave Dielectric ◽

Orthorhombic Perovskite

Crystal structure and microwave dielectric properties of Ca [(Li1/3Nb2/3) 0.95Zr0.05]O3−δ−xTiO2(0≤x≤0.1) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.02~0.1. With an increasing of Ti4+ content, the Qf value decreased due to a decrease of the degree of B-site 1:2 ordering. However, the τf value increased from-14.7ppm /°C to-6.9ppm/°C. When x=0.04, the optimum microwave dielectric properties: εr=31.1, Qf =21640GHz and τf =−8.8 ppm/°C.

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Effect of Nd2O3 on the Microwave Dielectric Properties of 0.67CaTiO3-0.33LaAlO3 Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.726.215 ◽

2017 ◽

Vol 726 ◽

pp. 215-219 ◽

Cited By ~ 1

Author(s):

Zhan Ming Dou ◽

Gan Wang ◽

Juan Jiang ◽

Tian Jin Zhang

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Solid State ◽

Solid State Reaction ◽

Perovskite Structure ◽

Single Phase ◽

Microwave Dielectric Properties ◽

Doping Amount ◽

Microwave Dielectric

0.67CaTiO3-0.33LaAlO3 ceramics doped with Nd2O3 were prepared using a conventional two-step solid-state reaction, and the effect of Nd2O3 doping on the microwave dielectric properties were studied. A single phase of perovskite structure was confirmed with the Nd2O3 doping. The results showed that the addition of Nd2O3 obviously improved the density and Q×f values of CTLA ceramics. The dielectric constant were almost not affected and the τf values were close to zero with the increase of the doping amount. CTLA ceramics with 0.2 wt% Nd2O3 doping sintered at 1380 °C for 4 h exhibited the optimal microwave dielectric properties of εr = 45.36, Q×f = 37,890 GHz, τf = 7.80 ppm/°C.

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