Microstructures and Photoluminescence in Nanocrystalline Barium Titanate

1998 ◽  
Vol 520 ◽  
Author(s):  
M. S. Zhang ◽  
J. Yu ◽  
W. F. Zhang ◽  
Z. Yin ◽  
W. C. Chen
Keyword(s):  
Barium Titanate ◽  
Ultrafine Particles ◽  
Critical Size ◽  
Hexagonal Phase ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Central Frequency ◽  
X Ray ◽  
Parameter Ratio ◽  
Tetragonal Phase Transition

ABSTRACTBarium titanate ultrafine particles are prepared by hydrothermal method at low temperature. Their phase structures and photoluminescence (PL) properties are examined by X-ray diffraction and Raman spectroscopy. The critical size of the cubic-tetragonal phase transition is about 48 nm and the lattice parameter ratio c/a equals 1.003. Strong photoluminescence is observed with central frequency located at 695 nm. The spectral behaviors at different annealing times and temperatures are studied. We attribute them to the semiconducting hexagonal phase embeded in the nanophase cubic BaTiO3to form trap centers and cause PL process.

Dielectric Properties of Barium Titanate Ceramics Modified by CuO in Different Methods

2012 ◽  
Vol 463-464 ◽  
pp. 276-280 ◽  
Author(s):  
Dan Su ◽  
Yu Wang ◽  
Wan Ping Chen ◽  
Helen Lai Wah Chan ◽  
Li Na Bing
Keyword(s):  
Barium Titanate ◽  
Curie Temperature ◽  
Perovskite Phase ◽  
Hexagonal Phase ◽  
Boundary Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pure Perovskite Phase ◽  
The Difference ◽  
Titanate Ceramics

CuO has been doped solely and together with BaO and SiO2 into barium titanate by mixing and calcination. X-ray diffraction showed that the sample doped by CuO-BaO has stable second hexagonal phase while the samples doped by CuO, CuO-SiO2 were of a pure perovskite phase. For CuO-BaO doping, the Curie temperature was decreased accompanied with higher εmax; while for CuO doping and CuO-SiO2 codoping, the Curie temperature was increased with εmax decreased. The difference can be explained considering that Cu2+ ion could not only incorporate into the BaTiO3 lattice, but also assemble in the boundary phase when CuO was doped solely. Besides, the mechanisms of CuO doping and SiO2 doping could happen at one time.

Growth temperature dependence of crystal symmetry in Nb-doped BaTiO3 thin films

2013 ◽  
Vol 03 (02) ◽  
pp. 1350009 ◽  
Author(s):  
Young Heon Kim ◽  
Xubing Lu ◽  
Marco Diegel ◽  
Roland Mattheis ◽  
Dietrich Hesse ◽  
...  
Keyword(s):  
Thin Films ◽  
Growth Temperature ◽  
Defect Density ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Threading Defects ◽  
Tetragonal Phase Transition

Growth temperature effects on the microstructure of Nb -doped BaTiO 3 thin films of the composition BaTi 0.98 Nb 0.02 O 3 are studied using X-ray diffraction and transmission electron microscopy (TEM). Reciprocal space maps and electron diffraction patterns show that the a-axis lattice parameter increases and the c-axis parameter decreases with increasing growth temperature, indicating a decrease of tetragonality. Bright-field TEM images show low and high densities of threading defects in films grown at low and high temperatures, respectively. The observations are discussed in terms of a hindering of the cubic-to-tetragonal phase transition by a high defect density and a high unit cell volume.

Microstructure Evolution During Mechanical Alloying of Face Centered Cubic Ti3Si Nanoparticles

2009 ◽  
Vol 6 ◽  
pp. 177-184
Author(s):  
Qiong Wu ◽  
Chang Sheng Li ◽  
Hua Tang ◽  
Xiao Hui Yu ◽  
Ke Sheng Cao ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Lattice Parameter ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Parameter Ratio ◽  
Transmission Electron ◽  
Si Nanoparticles ◽  
Amorphous Compounds ◽  
Face Centered

Face centered cubic Ti3Si nanoparticles were synthesized by mechanical alloying process and the structural and compositional evolutions during the mechanical alloying process were investigated by X-ray diffraction and High Resolution Transmission Electron Microscopy. The results showed that the lattice parameter ratio c/a and the unit cell volume of Ti(Si) were found to decrease with increasing milling time, indicating that the shrinkage of Ti lattice was caused by diffusion of Si atoms into Ti. After milling 51h, amorphous compounds were obtained by alloying Ti and Si powders, and the following mechanical alloying process crystallized the amorphous alloy to crystalline Ti3Si nanoparticles. These nanoparticles were predominantly crystalline with traces of the remnant amorphous phase.

scholarly journals Photoluminescent Properties of Hydroxyapatite and Hydroxyapatite/Multi-Walled Carbon Nanotube Composites

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 832
Author(s):  
Edna X. Figueroa-Rosales ◽  
Javier Martínez-Juárez ◽  
Esmeralda García-Díaz ◽  
Daniel Hernández-Cruz ◽  
Sergio A. Sabinas-Hernández ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Hexagonal Phase ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multi Walled Carbon Nanotube ◽  
Nanotube Composites ◽  
Carbon Nanotube Composites ◽  
Co Precipitation ◽  
Functionalized Mwcnts

Hydroxyapatite (HAp) and hydroxyapatite/multi-walled carbon nanotube (MWCNT) composites were obtained by the co-precipitation method, followed by ultrasound-assisted and microwave radiation and thermal treatment at 250 °C. X-ray diffraction (XRD) confirmed the presence of a hexagonal phase in all the samples, while Fourier-transform infrared (FTIR) spectroscopy elucidated the interaction between HAp and MWCNTs. The photoluminescent technique revealed that HAp and the composite with non-functionalized MWCNTs present a blue luminescence, while the composite with functionalized MWCNTs, under UV-vis radiation shows an intense white emission. These findings allowed presentation of a proposal for the use of HAp and HAp with functionalized MWCNTs as potential materials for optoelectronic and medical applications.

scholarly journals Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
First Principle ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Principle Calculations ◽  
Photodegradation Efficiency

AbstractIdeal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals.

scholarly journals Measurements by x-ray diffraction of the temperature dependence of lattice parameter and crystallite size for isostatically-pressed graphite

Carbon Trends ◽  
2021 ◽  
pp. 100071
Author(s):  
Keith R. Hallam ◽  
James Edward Darnbrough ◽  
Charilaos Paraskevoulakos ◽  
Peter J. Heard ◽  
T. James Marrow ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Crystallite Size ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray

Problems Associated with Kα Doublet in Residual Stress Measurements

1979 ◽  
Vol 23 ◽  
pp. 333-339
Author(s):  
S. K. Gupta ◽  
B. D. Cullity
Keyword(s):  
Residual Stress ◽  
Silicon Powder ◽  
Lattice Parameter ◽  
Diffraction Peak ◽  
Parameter Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
The Difference ◽  
Similar Accuracy

Since the measurement of residual stress by X-ray diffraction techniques is dependent on the difference in angle of a diffraction peak maximum when the sample is examined consecutively with its surface at two different angles to the diffracting planes, it is important that these diffraction angles be obtained precisely, preferably with an accuracy of ± 0.01 deg. 2θ. Similar accuracy is desired in precise lattice parameter determination. In such measurements, it is imperative that the diffractometer be well-aligned. It is in the context of diffractometer alignment with the aid of a silicon powder standard free of residual stress that the diffraction peak analysis techniques described here have been developed, preparatory to residual stress determinations.

scholarly journals MOVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics

2000 ◽  
Vol 5 (S1) ◽  
pp. 412-424
Author(s):  
Jung Han ◽  
Jeffrey J. Figiel ◽  
Gary A. Petersen ◽  
Samuel M. Myers ◽  
Mary H. Crawford ◽  
...  
Keyword(s):  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Optoelectronic Devices ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Peak Energy ◽  
Movpe Growth ◽  
Pl Emission

We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant- PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GaInN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

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