The DIA-type Kawai cell possesses a larger volume and a quasi-hydrostatic pressure environment and has been widely used in materials’ synthesis and x-ray diffraction experiments.However, few high-pressure in situ neu...The DIA-type Kawai cell possesses a larger volume and a quasi-hydrostatic pressure environment and has been widely used in materials’ synthesis and x-ray diffraction experiments.However, few high-pressure in situ neutron diffraction experiments were performed in the DIA-type Kawai cell because there is no wide window for neutron diffraction and the second-stage anvils and guild block material attenuates the neutron signal significantly.In this work, we tentatively modified the normal DIA-type Kawai cell(MA 2-6-8) into a MA 2-8 mode by removing the six first-stage tungsten carbide anvils.As a consequence, the eight tungsten carbide anvils(Kawai cell) are directly driven by the guide blocks.The results of ex situ and in situ pressure calibration show that the cell pressure can reach 5 GPa with small truncation edge lengths(TEL) of 3 mm even at the load of 300 kN.It suggests that this MA 2-8 cell may open a new way for high-pressure and high-temperature in situ neutron diffraction.展开更多
Tantalum nitride （TAN） compact with a Vickers hardness of 26 GPa is prepared by a high-pressure and high- temperature （HPHT） method. The crystal structure and atom occupations of WC-type TaN have been investigated...Tantalum nitride （TAN） compact with a Vickers hardness of 26 GPa is prepared by a high-pressure and high- temperature （HPHT） method. The crystal structure and atom occupations of WC-type TaN have been investigated by neutron powder diffraction, and the compressibility of WC-type TaN has been investigated by using in-situ high-pressure synchrotron x-ray diffraction. The third-order Birch-Murnaghan equation of state fitted to the x-ray diffraction pressure- volume （P-V） sets of data, collected up to 41 GPa, yields ambient pressure isothermal bulk moduli of B0 = 369（2） GPa with pressure derivatives of B~ = 4 for the WC-type TaN. The bulk modulus of WC-type TaN is not in good agreement with the previous result （Bo = 351 GPa）, which is close to the recent theoretical calculation result （Bo = 378 GPa）. An analysis of the experiment results shows that crystal structure of WC-type TaN can be viewed as alternate stacking of Ta and N layers along the c direction, and the covalent Ta-N bonds between Ta and N layers along the c axis in the crystal structure play an important role in the incompressibility and hardness of WC-type TaN.展开更多
In the present work, a third form, the so-called HP-BiNbO4 synthesized at high pressure and high temperature is investigated with the in-situ angle-dispersive x-ray diffraction（ADXRD） measurements under high pressur...In the present work, a third form, the so-called HP-BiNbO4 synthesized at high pressure and high temperature is investigated with the in-situ angle-dispersive x-ray diffraction（ADXRD） measurements under high pressure. We explore the compression behavior and phase stability of HP-BiNbO4. The structure of HP-BiNbO4 is first determined. The x-ray diffraction data reveal that the structure HP-BiNbO4 is stable under pressures up to 24.1 GPa. The ADXRD data yield a bulk modulus Ko = 185（7） GPa with a pressure derivative Ko＇= 2.9（0.8）. Furthermore, the data are compared with those of other ABO4 compounds. The results show that the bulk modulus of HP-BiNbO4（about 185 GPa） is slightly higher than that of tetragonal BiVO4 and significantly greater than those of the tungstates and molybdates.展开更多
The structural stability of Zn2GeO4 was investigated by in-situ synchrotron radiation angle dispersive x-ray diffraction. The pressure-induced amorphization is observed up to 10 GPa at room temperature. The high-press...The structural stability of Zn2GeO4 was investigated by in-situ synchrotron radiation angle dispersive x-ray diffraction. The pressure-induced amorphization is observed up to 10 GPa at room temperature. The high-pressure and hightemperature sintering experiments and the Raman spectrum measurement firstly were performed to suggest that the amorphization is caused by insufficient thermal energy and tilting Zn–O–Ge and Ge–O–Ge bond angles with increasing pressure,respectively. The calculated bulk modulus of Zn2GeO4 is 117.8 GPa from the pressure-volume data. In general, insights into the mechanical behavior and structure evolution of Zn2GeO4 will shed light on the micro-mechanism of the materials variation under high pressure and high temperature.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11427810)the National Key Research and Development Program of China(Grant No.2016YFA0401503)the Project for Science and Technology Plan of Sichuan Province,China(Grant No.2015GZ0053)
文摘The DIA-type Kawai cell possesses a larger volume and a quasi-hydrostatic pressure environment and has been widely used in materials’ synthesis and x-ray diffraction experiments.However, few high-pressure in situ neutron diffraction experiments were performed in the DIA-type Kawai cell because there is no wide window for neutron diffraction and the second-stage anvils and guild block material attenuates the neutron signal significantly.In this work, we tentatively modified the normal DIA-type Kawai cell(MA 2-6-8) into a MA 2-8 mode by removing the six first-stage tungsten carbide anvils.As a consequence, the eight tungsten carbide anvils(Kawai cell) are directly driven by the guide blocks.The results of ex situ and in situ pressure calibration show that the cell pressure can reach 5 GPa with small truncation edge lengths(TEL) of 3 mm even at the load of 300 kN.It suggests that this MA 2-8 cell may open a new way for high-pressure and high-temperature in situ neutron diffraction.
基金Project supported by the Research Foundation of Key Laboratory of Neutron Physics(Grant No.2015BB03)the National Natural Science Foundation of China(Grant Nos.11774247)+2 种基金the Science Foundation for Excellent Youth Scholars of Sichuan University(Grant No.2015SCU04A04)the Joint Usage/Research Center PRIUS(Ehime University,Japan)Chinese Academy of Sciences(Grant No.2017-BEPC-PT-000568)
文摘Tantalum nitride （TAN） compact with a Vickers hardness of 26 GPa is prepared by a high-pressure and high- temperature （HPHT） method. The crystal structure and atom occupations of WC-type TaN have been investigated by neutron powder diffraction, and the compressibility of WC-type TaN has been investigated by using in-situ high-pressure synchrotron x-ray diffraction. The third-order Birch-Murnaghan equation of state fitted to the x-ray diffraction pressure- volume （P-V） sets of data, collected up to 41 GPa, yields ambient pressure isothermal bulk moduli of B0 = 369（2） GPa with pressure derivatives of B~ = 4 for the WC-type TaN. The bulk modulus of WC-type TaN is not in good agreement with the previous result （Bo = 351 GPa）, which is close to the recent theoretical calculation result （Bo = 378 GPa）. An analysis of the experiment results shows that crystal structure of WC-type TaN can be viewed as alternate stacking of Ta and N layers along the c direction, and the covalent Ta-N bonds between Ta and N layers along the c axis in the crystal structure play an important role in the incompressibility and hardness of WC-type TaN.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472171 and 11427810)the Chinese Academy of Sciences(Grant Nos.KJCX2-SW-NO3 and KJCX2-SW-N20)
文摘In the present work, a third form, the so-called HP-BiNbO4 synthesized at high pressure and high temperature is investigated with the in-situ angle-dispersive x-ray diffraction（ADXRD） measurements under high pressure. We explore the compression behavior and phase stability of HP-BiNbO4. The structure of HP-BiNbO4 is first determined. The x-ray diffraction data reveal that the structure HP-BiNbO4 is stable under pressures up to 24.1 GPa. The ADXRD data yield a bulk modulus Ko = 185（7） GPa with a pressure derivative Ko＇= 2.9（0.8）. Furthermore, the data are compared with those of other ABO4 compounds. The results show that the bulk modulus of HP-BiNbO4（about 185 GPa） is slightly higher than that of tetragonal BiVO4 and significantly greater than those of the tungstates and molybdates.
基金Project supported by the Joint Fund of the National Natural Science Foundation of China and Chinese Academy of Sciences(Grant No.U1332104)
文摘The structural stability of Zn2GeO4 was investigated by in-situ synchrotron radiation angle dispersive x-ray diffraction. The pressure-induced amorphization is observed up to 10 GPa at room temperature. The high-pressure and hightemperature sintering experiments and the Raman spectrum measurement firstly were performed to suggest that the amorphization is caused by insufficient thermal energy and tilting Zn–O–Ge and Ge–O–Ge bond angles with increasing pressure,respectively. The calculated bulk modulus of Zn2GeO4 is 117.8 GPa from the pressure-volume data. In general, insights into the mechanical behavior and structure evolution of Zn2GeO4 will shed light on the micro-mechanism of the materials variation under high pressure and high temperature.
