Monoclinic phase of boron nitride appearing during the hexagonal cubic phase transition at high pressure and high temperature

1996 ◽  
Vol 68 (2) ◽  
pp. 182-184 ◽  
Author(s):  
Shigeo Horiuchi ◽  
Lian‐Long He ◽  
Mitsuko Onoda ◽  
Minoru Akaishi
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
High Temperature ◽  
Boron Nitride ◽  
Monoclinic Phase ◽  
Cubic Phase

Effects of High Pressure on the Luminescent Properties of Nanocrystalline and Bulk Y2O3:Eu3+

2008 ◽  
Vol 8 (3) ◽  
pp. 1404-1409 ◽  
Author(s):  
X. Bai ◽  
H. W. Song ◽  
B. B. Liu ◽  
Y. Y. Hou ◽  
G. H. Pan ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Surface Energy ◽  
Relative Intensity ◽  
Monoclinic Phase ◽  
Local Environment ◽  
Luminescent Properties ◽  
Cubic Phase ◽  
Spectral Changes ◽  
20 Nm

High pressure-induced spectral changes in a 20-nm cubic nanocrystalline yttria doped with europium and its corresponding bulk were studied in the range of 550–750 nm, corresponding to the 5D0 → 7FJ (J = 0–4) transitions. The results demonstrate that the bulk Y2O3 underwent phase transition from the cubic phase to the monoclinic phase as the pressure increased to 15 GPa, while the 20-nm nanocrystals did not. This can be concluded from the fact that the 5D0 → 7F0 line and the three 5D0 → 7F1 sublines originating from the cubic phase disappeared, while another group of 5D0 → 7F0 and 5D0 → 7F1 lines appeared. In addition, the relative intensity of the peak around 630 nm to that around 611 nm varied obviously as the pressure surpassed 15 GPa. The variations in the nanocrystals were more sluggish in comparison to those in the bulk, indicating that the nanocrystalline yttria had improved compressibility, which is attributed to an increased surface energy in nanocrystals. The local environment surrounding luminescent Eu3+ in the nanocrystals and the bulk both became more disordered with the increase of the pressure. The phase transition from the cubic to the monoclinic is irreversible.

Equation of state and phase transition of antigorite under high pressure and high temperature

2014 ◽  
Vol 228 ◽  
pp. 56-62 ◽  
Author(s):  
Cuiping Yang ◽  
Toru Inoue ◽  
Akihiro Yamada ◽  
Takumi Kikegawa ◽  
Jun-ichi Ando
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
High Temperature ◽  
Equation Of State

Cubic Boron Nitride as a New Semiconductor for Optoelectronics: Luminescence Properties and Potentialities

1989 ◽  
Vol 162 ◽  
Author(s):  
Koh Era ◽  
Osamu Mishima
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Boron Nitride ◽  
Room Temperature ◽  
Cubic Boron Nitride ◽  
Visible Region ◽  
Vibrational Structure ◽  
Luminescence Properties ◽  
Optoelectronic Applications ◽  
P Type

ABSTRACTIn cubic boron nitride made by high pressure and high temperature technique in our institute, we have found three luminescence bands in the ultraviolet and the short visible region at room temperature by cathode-ray excitation. They are: a band having vibrational structure and ascribable to undoped state of the crystal, a band ascribable to p-type doping and a band ascribable to n-type doping. Discussion is made on differences between the injection luminescence and the cathodoluminescence. Potentialities and difficulties in realizing the potentialities of cBN for optoelectronic applications are discussed.

scholarly journals Monitoring phase transition of aqueous biomass model substrates by high-pressure and high-temperature microfluidics

2019 ◽  
Vol 40 (4) ◽  
pp. 563-570 ◽  
Author(s):  
Renée M. Ripken ◽  
Stefan Schlautmann ◽  
Remco G.P. Sanders ◽  
Johannes G.E. Gardeniers ◽  
Séverine Le Gac
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
High Temperature ◽  
Monitoring Phase

Monoclinic-to-orthorhombic phase transition in Cu2(AsO4)(OH) olivenite at high temperature: strain and mode decomposition analyses

2018 ◽  
Vol 82 (2) ◽  
pp. 347-365 ◽  
Author(s):  
Serena C. Tarantino ◽  
Michele Zema ◽  
Athos M. Callegari ◽  
Massimo Boiocchi ◽  
Michael A. Carpenter
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Single Crystal ◽  
Volume Expansion ◽  
Monoclinic Phase ◽  
Orthorhombic Phase ◽  
Unit Cell ◽  
The Other ◽  
Unit Cell Parameters ◽  
Cell Parameters

ABSTRACTA natural olivenite single crystal was submitted to in situ high-temperature single-crystal X-ray diffraction from room temperature (RT) to 500°C. Unit-cell parameters were measured at regular intervals of 25°C, and complete datasets collected at T = 25, 50, 100, 150, 200, 250, 300, 400 and 500°C. Evolution of unit-cell parameters and structure refinements indicates that olivenite undergoes a structural phase transition from P21/n to Pnnm at ~200°C, and eventually becomes isostructural with the other members of the olivenite-mineral group. Volume expansion with temperature is larger in the monoclinic phase – where it follows a non-linear trend – than in the orthorhombic one. Axial and volume expansion coefficients of the orthorhombic olivenite phase are positive and linear and similar to those of the other Cu-bearing member of the mineral family, namely libethenite, but rather different from those of the Zn-analogue arsenate adamite.Distortion of Cu polyhedra is quite high in the olivenite monoclinic phase at RT and goes towards a relative regularization with increasing T until the phase transition occurs. In the orthorhombic phase, no significant variation of the polyhedral distortion parameters is observed with increasing temperature, and maximum expansion is along the b direction and governed by corner-sharing. Landau potential provides a good representation of the macroscopic changes associated with the phase transition, coupling between the strains and the order parameter is responsible for the nearly tricritical character of the transition.

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