Crystal structure and dielectric properties of a new Na2O-Nd2O3-CeO2 ceramic system at microwave frequencies

Journal Article · Thu Feb 15 04:00:00 EST 2018 · Materials Research Bulletin

DOI:https://doi.org/10.1016/J.MATERRESBULL.2017.09.064· OSTI ID:22805377

Liu, Fei ^[1]; Qu, Jingjing ^[2]; Yuan, Changlai; Chen, Guohua ^[3]

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1. School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin 541004 (China)
2. Department of Computer Science and Engineering, Guilin University of Aerospace Technology, Guilin 541004 (China)
3. Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004 (China)

Highlights: • A large amount of Na evaporation can make τ{sub f} more negative in present ceramics. • Na-excess evaporation results in the formation of Ce{sub 1-x}Nd{sub x}O{sub 2-x/2} solid solution. • Ce{sub 1-x}Nd{sub x}O{sub 2-x/2} (x = 0.25 and 0.5) solid solutions belong to the same fluorite-type. - Abstract: Na{sub 2}O-Nd{sub 2}O{sub 3}-CeO{sub 2} ceramic systems of the form Na{sub 3x−1}Nd{sub 1−x}CeO{sub 3} (x = 0.4, 0.5, and 0.6) were prepared via a solid-state reaction method. X-ray diffraction analyses indicated that the samples with x = 0.4, 0.6 and those with x = 0.5 formed Nd{sub 0.25}Ce{sub 0.75}O{sub 1.875} and Nd{sub 0.5}Ce{sub 0.5}O{sub 1.75} solid solutions, respectively, which resulted from a large degree of Na{sup +} ion evaporation. Both the Nd{sub 0.25}Ce{sub 0.75}O{sub 1.875} and Nd{sub 0.5}Ce{sub 0.5}O{sub 1.75} phases belonged to the same cubic structure with an Fm-3m (225) space group. Additionally, the microstructures, sintering behaviors, and microwave dielectric properties were considered to be strongly related to the Na content in the Na{sub 3x−1}Nd{sub 1−x}CeO{sub 3} ceramics. A relatively large degree of Na{sup +} ion evaporation could increase the negative temperature coefficient of the resonant frequency (τ{sub f}) for these ceramic systems. Moreover, after sintering at 1380 °C for 2 h, the x = 0.6 specimen possessed a low permittivity (ε{sub r}) of approximately 9.13, a moderate quality factor (Q × f) of approximately 23,800 GHz (at 9.14 GHz) and a negative τ{sub f} value of approximately −61.7 ppm/°C. As a result, it could be a promising microwave dielectric material for achieving a near-zero τ{sub f} value by solidifying one or more microwave dielectric ceramics with a high positive τ{sub f} value.

• OSTI ID: 22805377
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Vol. 98; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CERAMICS
CERIUM OXIDES
CRYSTAL STRUCTURE
DIELECTRIC MATERIALS
FLUORITE
GHZ RANGE
MICROSTRUCTURE
MICROWAVE RADIATION
NEODYMIUM OXIDES
PERMITTIVITY
QUALITY FACTOR
SINTERING
SODIUM IONS
SODIUM OXIDES
SOLID SOLUTIONS
SPACE GROUPS
TEMPERATURE COEFFICIENT
X-RAY DIFFRACTION