Mixed Metal Oxides

Ward, Roland

doi:10.1002/9780470166024.ch7

“…Semiconducting materials have been the focus of many studies due to their integral role in the microelectronic industry [1]. Among these, lanthanum ferrite, LaFeO 3 , is an important inorganic compound known for its diverse applications in the field of electronics.…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of calcium-substituted lanthanum ferrite

Andoulsi-Fezei

¹

,

Sdiri

²

,

Horchani−Naifer

³

et al. 2020

Journal of Asian Ceramic Societies

7

0

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Among La 1-x Ca x FeO 3-δ (0 ≤ x ≤ 0.5) compounds, the optimal value of the direct current conductivity was registered for a 20% substituted amount. We therefore attempted to study the impedance and dielectric properties of 20% calcium-substituted lanthanum ferrite. We investigated the electric properties in depth between 5 Hz and 13 MHz from 350 to 800°C. The results reveal interesting properties. Indeed, the perovskite shows a huge dielectric constant which promotes its utilization in high-performance dielectric material applications. At a given temperature, ε' and tan(δ) decrease with increases in frequency. This trend was explained based on the Maxwell Wagner polarization model. The variations in dielectric loss (ε") with frequency obey the Giuntini theory based on the hopping model. As the temperature increases from 350 to 800°C, the binding energy increases from 0.22 to 0.34 eV, while the minimum hopping distance decreases from 2.16 to 0.12 pm. Consideration of the electric modulus analyzes showed that the relaxation mechanism is dominated at below 400°C by a shortrange movement of charge carriers, whereas at above that temperature, a long-range movement of charge carriers is dominant. This study presents a solid foundation for the polarization and dielectric properties of lanthanum ferrite, which is a lead-free, environmentally friendly material and a promising candidate for use in nonlinear optical applications and microwave devices.

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Oxides: Solid‐State Chemistry

McCarroll

¹

,

Ramanujachary

²

2005

Encyclopedia of Inorganic Chemistry

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This article is an overview of the solid‐state chemistry of oxides. It starts with a brief description of the periodic trends associated with compounds of oxygen and is followed by a discussion of the principle of the closest packing of spheres that can be used to describe ionic structures. An in depth description of several structure types, important in solid‐state oxide chemistry, follows, and covers the important binary structures as well as several ternary structures including the Perovskite, Spinel, Garnet, Pyrochlore, and Scheelite structures. Selected special topics in solid‐state oxide chemistry include a discussion of crystallographic shear structures, defect oxides, and tungsten and molybdenum bronzes, intergrowth structures of which the high‐temperature superconductor YBa 2 Cu 3 O 7 is an example. The importance of structure‐property relations in oxides is illustrated by a discussion of metal–metal bonds in oxides, electronic conduction in a variety of oxides, and the catalytic properties of defect scheelites. A lengthy discussion is devoted to the various means used by solid‐state chemists to synthesize oxides not only as bulk polycrystalline phases but as single crystals and thin films as well that are so important to electronic applications. The article concludes with a discussion of several important practical applications of oxides including magnetic oxides, oxide sensors, luminescent materials, ferroelectrics, CMR oxides, optical materials, ceramics, and refractory materials as well as a brief overview of other important uses. Because this is a survey article, in depth discussion of many properties of oxides is not possible. However, many of these topics are covered in depth in other parts of the Encyclopedia and the reader will find the cross references helpful. A substantial list of references also provides a gateway to the solid‐state literature.

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Oxides: Solid‐State Chemistry

McCarroll¹,

Ramanujachary²

2005

Encyclopedia of Inorganic and Bioinorganic Chemistry

2

0

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This article is an overview of the solid‐state chemistry of oxides. It starts with a brief description of the periodic trends associated with compounds of oxygen and is followed by a discussion of the principle of the closest packing of spheres that can be used to describe ionic structures. An in depth description of several structure types, important in solid‐state oxide chemistry, follows, and covers the important binary structures as well as several ternary structures including the Perovskite, Spinel, Garnet, Pyrochlore, and Scheelite structures. Selected special topics in solid‐state oxide chemistry include a discussion of crystallographic shear structures, defect oxides, and tungsten and molybdenum bronzes, intergrowth structures of which the high‐temperature superconductor YBa 2 Cu 3 O 7 is an example. The importance of structure‐property relations in oxides is illustrated by a discussion of metal–metal bonds in oxides, electronic conduction in a variety of oxides, and the catalytic properties of defect scheelites. A lengthy discussion is devoted to the various means used by solid‐state chemists to synthesize oxides not only as bulk polycrystalline phases but as single crystals and thin films as well that are so important to electronic applications. The article concludes with a discussion of several important practical applications of oxides including magnetic oxides, oxide sensors, luminescent materials, ferroelectrics, CMR oxides, optical materials, ceramics, and refractory materials as well as a brief overview of other important uses. Because this is a survey article, in depth discussion of many properties of oxides is not possible. However, many of these topics are covered in depth in other parts of the Encyclopedia and the reader will find the cross references helpful. A substantial list of references also provides a gateway to the solid‐state literature.

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Mixed Metal Oxides

Cited by 9 publications

References 152 publications

Dielectric properties of calcium-substituted lanthanum ferrite

Dielectric properties of calcium-substituted lanthanum ferrite

Oxides: Solid‐State Chemistry

Oxides: Solid‐State Chemistry

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