The (BMN) bulk materials were sintered at 1050°C, 1100°C,
1150°C, 1200°C by the conventional ceramic process, and their microstructure and
dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray
diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM)
(including the X-ray energy dispersive spectrometry EDS and high resolution
transmission electron microscopy HRTEM) and dielectric impedance analyzer.
We systematically investigated the structure, dielectric properties and voltage
tunable property of the ceramics prepared at different sintering temperatures. The XRD
patterns demonstrated that the synthesized BMN solid solutions had cubic phase
pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter
(a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The
vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed
the cubic phase pyrochlore-type structure of the synthesized BMN. According to the
Scanning Electron Microscope (SEM) images, the grain size increased with increasing
sintering temperature. Additionally, it was shown that the densities of the BMN ceramic
tablets vary with sintering temperature. The calculated theoretical density for the BMN
ceramic tablets sintered at different temperatures is about 6.7521 . The density
of the respective measured tablets is usually amounting more than 91% and
5
approaching a maximum value of 96.5% for sintering temperature of 1150°C. The
microstructure was investigated by using Scanning Transmission Electron Microscope
(STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and
XRD, the impact of sintering temperature on the macroscopic and microscopic structure
was discussed.
The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid
solutions were measured to be 161-200 and (at room temperature and
100Hz-1MHz), respectively. The BMN solid solutions have relative high dielectric
constant and low dielectric loss. With increasing sintering temperature, the dielectric
constant showed the maximum at 1150°C. The leakage current of BMN ceramic material
is extraordinary small. When the voltage and thickness of the BMN capacitor are 4000V
and 300um, the leakage current amounts only about 0.13-0.65 . The excellent
physical and electrical properties make BMN thin films promising for potential tunable
capacitor applications.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/293689 |
| Date | 05 1900 |
| Creators | Li, Yangyang |
| Contributors | Al-Kassab, Talaat, Physical Science and Engineering (PSE) Division, Alshareef, Husam N., Rothenberger, Alexander |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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