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| 1 | First-order phase transition and unexpected rigid rotation mode in hybrid improper ferroelectric(La,Al)co-substituted Ca_(3)Ti_(2)O_(7) ceramics显示文摘Ca_(3)Ti_(2)O_(7) with Ruddlesden-Popper structure exhibits the largest polarization among the known hybrid improper ferroelectrics.However,the high Curie temperature impedes the thorough study of phase transition through dielectric characterization.According to the previous theoretical design rule,the Curie temperature can be suppressed by increasing the tolerance factor.So,in the present work,high-quality Ca_(3-x)LaxTi_(2-x)Al_(x)O_(7)(x=0.0,0.1,0.2,0.3)ceramics with increased tolerance factors were successfully prepared.The amplitude of oxygen octahedral tilt mode indeed decreases with increasing tolerance factors,leading to a degeneration of ferroelectric polarization.However,the unexpected rigid rotation mode causes the composition-invariable coercive fields.The Curie temperatures decrease linearly with increasing x and tolerance factors.The variable-temperature dielectric constant confirms first-order improper ferroelectric transitions in Ca_(3)Ti_(2)O_(7)-based ceramics.The results of variable temperature Xray diffraction reveal the coexistence of two-phases below Curie temperature.The present work confidently confirms the first-order improper ferroelectric transition in Ca_(3)Ti_(2)O_(7)-based ceramics by combining results of variable-temperature dielectric response and in-situ X-ray powder diffraction. | Z.Z.Hu J.J.Lu B.H.Chen T.T.Gao X.Q.Liu W.Wen X.M.Chen | 2019 | Journal of Materiomics2019，5，4： | 4 |
| 2 | Thermodynamic analysis of hydrogen production via glycerol steam reforming with CO2 adsorption显示文摘 | Y.H.Li W.J.Wang B.H.Chen | | 0，，： | 1 |
| 3 | Room-temperature ferroelectricity in A-site ordered Ruddlesden-Popper Li_(2)CaTa_(2)O_(7) ceramics显示文摘In the present work,the crystal structure,ferroelectric and dielectric properties of the dense single-phase Li_(2)CaTa_(2)O_(7) ceramics with A-site ordered double-layer Ruddlesden-Popper structures have been investigated by the experiments and first-principles calculations.A polar Pna21 phase was determined by the Rietveld refinement against the X-ray diffraction pattern at room temperature,and it was confirmed by its lowest calculated energy and rigid phonon modes.The ferroelectricity was found by observing the ferroelectric hysteresis loop at room temperature,and its remanent polarization was similar to the value calculated from the Berry phase and Born effective charge approaches.The ferroelectricity is a nonconventional proper one since its polarization is induced from the displacement of oxygen anions instead of tantalum cations based on the individual atomic polarization.A first-order transition from an antiferroelectric to paraelectric phase around 900 K was found by the DSC and variable-temperature dielectric measurements.From the present work,the room-temperature ferroelectricity is experimental confirmed in the present ceramics,inspiring the search for new ferroelectricity in the ceramics with A-site ordered Ruddlesden-Popper structures. | B.H.Zhang Z.Z.Hu B.H.Chen X.Q.Liu X.M.Chen | 2020 | Journal of Materiomics2020，6，3： | 0 |
| 4 | INVERSE CIRCULATING THERMOSYPHON EVAPORATOR显示文摘In this paper,the mechanism of operation of an inverse circulating thermosyphon evaporator isproposed.The performance characteristics of this novel evaporator have been studied experimentally andtheoretically,The inverse circulating thermosyphon evaporators have higher heat transfer coefficient and longeroperation period in comparison with ordinary circulating ordinary circulating evaporators. | 沙庆云 仝爱星 李淞平 沈自求 B.H.Chen | 1994 | Chinese Journal of Chemical Engineering1994，2，1： | 0 |
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