scholarly journals Influence of heat treatment on photoluminescence spectra in ZnS:Mn crystals with hexagonal structure

2018 ◽  
Vol 26 (1) ◽  
pp. 73-76
Author(s):  
O. V. Kovalenko ◽  
O. V. Khmelenko ◽  
Ye. G. Plakhtii
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Heat Treatment ◽  
Photoluminescence Spectrum ◽  
Hexagonal Structure ◽  
Zinc Sulphide ◽  
Maximum Intensity ◽  
Photoluminescence Spectra ◽  
Individual Bands ◽  
The Individual

It has been investigated the influence of heat treatment with the following temperins on the integral photoluminescence spectra and on the individual bands of this spectra. It has been showed the correlation between the changes of intensity of photoluminescence individual bands and real structure of crystal, controlled with the help of EPR method. The basic changes of photoluminescence and structural properties have threshold nature. They begin to show up at temperature of annealing T > 650o С. The maximum intensity of integral photoluminescence spectrum was observed in the region of phase transition crystal structure of zinc sulphide.

Synthesis of Tetragonal BaTiO3 Powders via Alkoxide Method Assisted by Diethanolamine

2013 ◽  
Vol 442 ◽  
pp. 88-93
Author(s):  
Yu Tao Li ◽  
Ke Hui Qiu ◽  
Yu Chong Qiu ◽  
Hui Zhong ◽  
Ning Jia Fu
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Heat Treatment ◽  
Transition Process ◽  
Target Product ◽  
Calcination Time ◽  
Synthesis Parameters ◽  
Phase Transition Process ◽  
Alkoxide Method ◽  
Tetragonal Batio

The BaTiO3 precursor was prepared by alkoxide method, in which barium hydroxide octahydrate and butyl titanate were chosen as the Ba and Ti sources, and diethanolamine (DEA) as the polymerizing agent respectively. In order to determine the synthesis parameters of the target product, the phase transition process of the precursor with temperature increasing was investigated by TG-DTA. The effect of calcination temperature, the dosage of DEA and calcination time on the phase compositions and crystal structure of the synthesized samples were investigated by XRD. The results indicate that DEA can promote the formation of tetragonal BaTiO3 effectively, and the high-purity tetragonal BaTiO3 was obtained by heat treatment of the precursor at 1100°C for 3h with 1mL DEA dosage.

Optical Properties of Co-Doped Zno Nano Powder Material Prepared by Ball Milling

2011 ◽  
Vol 143-144 ◽  
pp. 190-193
Author(s):  
Song Ning Xu ◽  
Z.Q. Cai ◽  
N.K. Sun ◽  
Y.B. Gao ◽  
F. Liu
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Ball Milling ◽  
Blue Emission ◽  
Peak Position ◽  
Hexagonal Structure ◽  
Photoluminescence Spectra ◽  
Doped Zno ◽  
Zno Crystal ◽  
Co Doped

Zn1-xCoxO nano powders have been successfully prepared by ball milling and have been annealing at 600°C. The crystal structure and optical properties of sample were characterized by X-ray diffraction (XRD), photoluminescence spectra (PL) and ultraviolet visible light absorption spectra (UV), and the formation mechanism was discussed. Co-doped ZnO nano powders exhibit wurtzite (hexagonal) structure. Co2+enters into ZnO crystal structure and substitutes for Zn2+. All samples show typical luminescence behavior with about 396nm UV emission peak. In addition, the about 450nm and 470nm blue emission peaks are found in photoluminescence spectra. Before the doped content is within 8at%, the band edge of ultraviolet absorption appears red shift phenomenon with the increase of doping content. The peak position was shifted from 362nm (3.43eV) to 367nm (3.38eV). Annealing is in favor of the replacement that Co2+enters into ZnO crystal structure and substitutes for Zn2+

Dynamic low-dose electron diffraction and imaging of phase transitions in polymers

1993 ◽  
Vol 51 ◽  
pp. 890-891
Author(s):  
David C. Martin ◽  
Jun Liao
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Electron Diffraction ◽  
Low Dose ◽  
Dark Field ◽  
Continuous Change ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Chain Axis ◽  
High Resolution Electron Micrographs

By careful control of the electron beam it is possible to simultaneously induce and observe the phase transformation from monomer to polymer in certain solid-state polymcrizable diacetylenes. The continuous change in the crystal structure from DCHD diacetylene monomer (a=1.76 nm, b=1.36 nm, c=0.455 nm, γ=94 degrees, P2l/c) to polymer (a=1.74 nm, b=1.29 nm, c=0.49 nm, γ=108 degrees, P2l/c) occurs at a characteristic dose (10−4C/cm2) which is five orders of magnitude smaller than the critical end point dose (20 C/cm2). Previously we discussed the progress of this phase transition primarily as observed down the [001] zone (the chain axis direction). Here we report on the associated changes of the dark field (DF) images and selected area electron diffraction (SAED) patterns of the crystals as observed from the side (i.e., in the [hk0] zones).High resolution electron micrographs (HREM), DF images, and SAED patterns were obtained on a JEOL 4000 EX HREM operating at 400 kV.

crystal structure and phase transition in the compound [C6H5CH2NH2CH3]10Sb6Cl28

2006 ◽  
Vol 31 (1) ◽  
pp. 39-48
Author(s):  
Najla Vix-Gurtel ◽  
Chaari Dentzer ◽  
Slaheddine Chaabouni ◽  
Jean-Michel Savariault ◽  
Abdelhamid ben Salah
Keyword(s):  
Crystal Structure ◽  
Phase Transition

Ab-initio investigation of crystal structure and pressure induced phase transition in ThO2 and PuO2

2021 ◽  
pp. 102579
Author(s):  
Shilpa Singh ◽  
Yogesh Sonvane ◽  
K.A. Nekrasov ◽  
A.S. Boyarchenkov ◽  
A. Ya. Kupryazhkin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Ab Initio

Rem and Rheed Studies of Pb Adsorption on Si(111)

1992 ◽  
Vol 280 ◽  
Author(s):  
Yasumasa Tanishiro ◽  
Masahiko Fukuyamaand ◽  
Katsumichi Yagi
Keyword(s):  
Phase Transition ◽  
Heat Treatment ◽  
Phase Diagram ◽  
Surface Structures ◽  
Structure Changes ◽  
Incommensurate Structures

ABSTRACTStructure changes of Si(111)-Pb surfaces due to deposition and heat treatment are studied by REM-RHEED. Surface structures observed are summarized as a phase diagram. Formation of an incommensurate layer(α) and a phase transition between incommensurate structures of α and α' is described.

scholarly journals Temperature Dependence of Electrical Properties and Crystal Structure of 0.29Pb(In1/2Nb1/2)O3–0.44Pb(Mg1/3Nb2/3)O3–0.27PbTiO3Single Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Qian Li ◽  
Yun Liu ◽  
Andrew Studer ◽  
Zhenrong Li ◽  
Ray Withers ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Electrical Properties ◽  
Dielectric Permittivity ◽  
Neutron Diffraction ◽  
Electrical Measurement ◽  
Temperature Dependent ◽  
Electromechanical Properties ◽  
Polar Order

We characterized the temperature dependent (~25–200°C) electromechanical properties and crystal structure of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3single crystals usingin situelectrical measurement and neutron diffraction techniques. The results show that the poled crystal experiences an addition phase transition around 120°C whereas such a transition is absent in the unpoled crystal. It is also found that the polar order persists above the maximum dielectric permittivity temperature at which the crystal shows a well-defined antiferroelectric behavior. The changes in the electrical properties and underlying crystal structure are discussed in the paper.

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