scholarly journals Phase diagram of (Na0.5K0.5)NbO3-(Bi0.5Na0.5)ZrO3 solid solution

2016 ◽  
Vol 06 (02) ◽  
pp. 1650014 ◽  
Author(s):  
Ruiping Wang ◽  
Mitsuru Itoh
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Solid Solution ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
A Site ◽  
T Phase ◽  
O Phase

Phase diagram of [Formula: see text]Na[Formula: see text]K[Formula: see text]NbO3–x(Bi[Formula: see text]Na[Formula: see text]ZrO3 solid solution has been established from dielectric constant measurements and structure analyses. It is found that with increasing x, the C–T phase transition temperature [Formula: see text] and the T–O phase transition temperature [Formula: see text] decrease, while the [Formula: see text] phase transition temperature [Formula: see text] increases. [Formula: see text] of NKN–xBNZ is much different from that of NKN–xBZ solid solution. The result could be mainly elucidated by the hybridization between the A-site ion and oxygen.

Change of Phase Transition Temperature in Band Engineered Ferroelectric Lanthanum-Modified Bismuth Titanates

2020 ◽  
Vol 20 (11) ◽  
pp. 7135-7139
Author(s):  
Rui Tang ◽  
Sangmo Kim ◽  
Chung Wung Bark
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Ferroelectric Properties ◽  
Solar Spectrum ◽  
Ferroelectric Material ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Increasing Temperature

The ferroelectric material chosen for a solar cell has to absorb as much of the solar spectrum as possible, therefore a low band gap is desirable, but it is rarely known for phase transition temperature on the bandgap engineered ferroelectric materials. The phase transition temperature of a ferroelectric material can be determined by monitoring its dielectric constant with increasing temperature, as the dielectric constant changes abruptly at the phase transition temperature. Here, we inform the measurement of the phase transition temperature of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 as well as cobalt and iron doped Bi3.25La0.75Ti3O12 bulk ceramics for photovoltaic cells based on dielectric monitoring with changing temperature. We synthesized lanthanum-modified bismuth-titanate-based ceramics with various doping concentrations transition metal to Ti. X-ray diffraction analysis revealed that all the compounds crystallized in an orthorhombic structure. Their morphologies and size distributions were observed using scanning electron microscopy. From the ultraviolet-visible spectroscopy absorption spectra of the synthesized powder, bandgaps were checked. An inductance-capacitance-resistance meter was used to obtain the relationship between dielectric responses and the temperature of the targets in a tube furnace. We observed that the dielectric constant increases gradually with increasing temperature, until the transition temperature and subsequently decreases, and we were able to determine the phase transition temperatures of the tested materials. Furthermore, the results revealed that all the doped bismuth titanates keep their phase transition temperatures, which were sufficiently high, to maintain their ferroelectric properties above room temperature.

The Effect of the Lipid Bilayer State on Fluorescence Intensity of Fluorescein-PE in a Saturated Lipid Bilayer

2000 ◽  
Vol 55 (5-6) ◽  
pp. 418-424 ◽  
Author(s):  
Marek Langner ◽  
Hanna Pruchnik ◽  
Krystian Kubica
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Lipid Bilayer ◽  
Phase Transition Temperature ◽  
Conformational Changes ◽  
Fluorescence Intensity ◽  
Electrostatic Potential ◽  
Salt Concentration ◽  
Membrane Interface

Fluorescein-PE is a fluorescence probe that is used as a membrane label or a sensor of surface associated processes. Fluorescein-PE fluorescence intensity depends not only on bulk pH, but also on the local electrostatic potential, which affects the local membrane interface proton concentration. The pH sensitivity and hydrophilic character of the fluorescein moiety was used to detect conformational changes at the lipid bilayer surface. When located in the dipalmitoylphosphatidylcholine (DPPC) bilayer, probe fluorescence depends on conformational changes that occur during phase transitions. Relative fluorescence intensity changes more at pretransition than at the main phase transition temperature, indicating that interface conformation affects the condition in the vicinity of the membrane. Local electrostatic potential depends on surface charge density, the local dielectric constant, salt concentration and water organisation. Initial increase in fluorescence intensity at temperatures preceding that of pretransition can be explained by the decreased value of the dielectric constant in the lipid polar headgroups region related in turn to decreased water organisation within the membrane interface. The abrupt decrease in fluorescence intensity at temperatures between 25 °C and 35 °C (DPPC pretransition) is likely to be caused by an increased value of the electrostatic potential, induced by an elevated value of the dielectric constant within the phosphate group region. Further increase in the fluorescence intensity at temperatures above that of the gel-liquid phase transition correlates with the calculated decreased surface electrostatic potential. Above the main phase transition temperature, fluorescence intensity increase at a salt concentration of 140 m M is larger than with 14 m M . This results from a sharp decline of the electrostatic potential induced by the phosphocholine dipole as a function of distance from the membrane surface.

High-Performance Lead-Free Barium Titanate Piezoelectric Ceramics

2008 ◽  
Vol 54 ◽  
pp. 7-12 ◽  
Author(s):  
Tomoaki Karaki ◽  
Masatoshi Adachi ◽  
Kang Yan
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Barium Titanate ◽  
Phase Transition Temperature ◽  
Room Temperature ◽  
Electromechanical Coupling ◽  
Electromechanical Coupling Factor ◽  
Coupling Factor ◽  
Piezoelectric Constants

Barium titanate (BaTiO3) ceramics with a high-density were fabricated by two-step sintering method from hydrothermally synthesized 100 nm BaTiO3 nano-particles. The best specimen with an average grain size of 1.6 μm and a density of 5.91 g/cm3 (98.3% of the theoretical value). The dielectric constant was 4500 and electromechanical coupling factor kp was 45%. Large piezoelectric constants d33 = 460 pC/N and d31 = -185 pC/N were observed in the specimens. This was an important practical result towards obtaining a high d33 in non-lead-based BaTiO3 ceramics manufactured by a low-cost process. These results also indicated the possibility of using BaTiO3 ceramics in piezoelectric devices at room temperature. Temperature dependence of dielectric constant showed two peaks located at 24 and 126 oC, corresponding to orthorhombic-to-tetragonal phase transition temperature Tot and Curie temperature Tc, respectively. Owing to the size effect of nanocrystals, Tot shifted to 24 oC. The maximum of electromechanical coupling factor kp appeared close to the phase transition temperature. It also caused a very large temperature coefficient of resonance frequency from room temperature to 60 oC. Hysteresis curve measurement showed a very low coercive field Ec = 115 V/mm. A large Poisson’s ratio, about 0.38, was determined from the ratio of overtone frequency and resonant frequency in the planar mode. The high Poisson’s ratio and the large dielectric constants are most likely the origin of the high piezoelectric constants in the ceramics.

Tuning the phase transition temperature of Cr2(MoO4)3 by A-site substitution of scandium

2018 ◽  
Vol 44 (18) ◽  
pp. 22165-22171 ◽  
Author(s):  
Zhiping Zhang ◽  
Weikang Sun ◽  
Qian Zheng ◽  
Hongfei Liu ◽  
Min Zhou ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
A Site

Phase Transition Temperatures of Divalent and Trivalent Ions Substituted (Bi1/2Na1/2)TiO3 Ceramics

2007 ◽  
Vol 350 ◽  
pp. 93-96 ◽  
Author(s):  
Yuji Hiruma ◽  
Yoshinori Watanabe ◽  
Hajime Nagata ◽  
Tadashi Takenaka
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Electrical Measurement ◽  
Transition Temperatures ◽  
Maximum Dielectric Constant ◽  
Phase Transition Temperatures ◽  
Temperature Dependences ◽  
A Site ◽  
The Relationship

The phase transition temperatures of divalent and trivalent ions substituted (Bi1/2Na1/2)TiO3 ceramics were investigated in detail by electrical measurement. BNT ceramics substituted by divalent (Ca2+, Sr2+ and Ba2+) and trivalent (La3+, Nd3+, Ho3+ and Yb3+) ions were prepared by conventional ceramic fabrication process. For these ceramics, the depolarization temperature, Td, the rhombohedral-tetragonal phase transition temperature, TR-T, and the temperature of the maximum dielectric constant, Tm, were determined on the basis of the temperature dependences of dielectric and piezoelectric properties. In this study, we demonstrated the relationship between phase transition temperature and ionic radius of ions substituted in the A-site of BNT ceramics.

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