Dilatometric Study of the Isotropic-Smectic F Transition of 10O.14

1994 ◽  
Vol 49 (4-5) ◽  
pp. 559-562
Author(s):  
N. V. S. Rao ◽  
G. Padmaja Rani ◽  
D. M. Potukuchi ◽  
V. G. K. M. Pisipati
Keyword(s):  
Phase Transition ◽  
Exponential Growth ◽  
Large Temperature ◽  
First Order ◽  
Temperature Range ◽  
Dilatometric Study ◽  
Dilatometric Studies

Abstract The compound N(p-n-decyloxy benzylidene)p-n-tetradecyl aniline, (10O.14), a higher hom ologue of the MBBA series, exhibits smectic F and smectic G phases. Dilatometric studies inferred strong pre-transitional effects in a large temperature range. DSC results confirmed the first order nature of the IF and FG transitions. The exponential growth of continuous six fold hexagonal order across the isotropic-smectic F phase transition is estimated from the density studies with an exponent b = 0.75.

Synthesis, Characterization and Phase Transition Studies on Some N-(4-Butyloxy Benzylidene)-4-Alkoxy Anilines, 4O.Om Compounds - A Dilatometric Study

2013 ◽  
Vol 2 (1) ◽  
pp. 38-47
Author(s):  
Venkata Pisipati ◽  
M. Saraswathi ◽  
D. Madhavi Latha ◽  
P. Pardhasaradhi ◽  
P. V. Datta Prasad
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimeter ◽  
Nematic Phase ◽  
The Body ◽  
Transition Temperatures ◽  
First Order ◽  
Dilatometric Study ◽  
Dilatometric Studies ◽  
Transition Studies

Dilatometric studies are carried out on the synthesized N-(4-butyloxy benzylidene)-4-alkoxy anilines, 4O.Om compounds with the m = 3 to 7 and 9. Characterization of these compounds is done using the polarizing microscope attached with a hot stage. The differential scanning calorimeter is employed to find out the transition temperatures as well as the heats of transitions. All the compounds exhibit nematic phase with varying thermal ranges with the clearing temperatures are above 100 OC as unlike the case of the well known N-(4-butyloxy benzylidene)-4-alkyl anilines, 4O.m compounds which exhibit rich poymorphysim and the clearing temperatures are well below 100 OC. As expected the isotropic to nematic transition exhibited first order nature and the results are discussed with the body of the data available in literature.

Ultrasonic Relaxation in Phase Transition Region in Ferroelectric Semiconductors of Sn2P2S6 Family

2012 ◽  
Vol 184 ◽  
pp. 345-350
Author(s):  
Vytautas Samulionis ◽  
Juras Banys ◽  
Yulian Vysochanskii
Keyword(s):  
Phase Transition ◽  
Ultrasonic Velocity ◽  
Thermal Hysteresis ◽  
Ultrasonic Attenuation ◽  
Landau Theory ◽  
Velocity Change ◽  
First Order ◽  
Temperature Range ◽  
Large Hysteresis ◽  
Relative Change

The paper presents recent results of ultrasonic investigation of Sn2P2S6 family ferroelectric crystals and their solid solutions in the temperature range 100-300 K. It was shown that in Sn2P2(S,Se)6 crystals the critical ultrasonic velocity slowing down for longitudinal waves propagating along main crystallographic directions is quite sharp and large. The relative change of longitudinal ultrasonic velocity along z-axis at the phase transition gradually increased from 10 % in pure Sn2P2S6 till 25 % for sample with 0.4 content of Se. Such large velocity change causes the large ultrasonic attenuation anomaly. The increase of relaxation time: τ=τ0/(TC-T) leads to the increase of attenuation. Prefactor τ0 was shown to be very small and the critical attenuation anomaly arises in the narrow temperature range close to phase transition. In the 0.4 Se sample the phase transition is of the first order because small thermal hysteresis exists. The ultrasonic velocity behaviour in the ferroelectric phase was described using Landau theory and free energy expansion including sixth order terms. For (Sn,Pb)2P2S6 system the critical ultrasonic anomalies were smaller and the phase transition temperature substantially decreased (for 0.45 Pb sample the phase transition point was at Tc =140 K). The ultrasonic anomalies at phase transition in (PbxSn1-x)2P2S6 have large hysteresis showing that transition is of the first order, far from the critical point.

scholarly journals PRETRANSITIONAL PHENOMENA IN REGION OF STRUCTURAL PHASE TRANSITION IN SODIUM PERCHLORATE

2019 ◽  
Vol 63 (1) ◽  
pp. 64-70
Author(s):  
Amil R. Aliev ◽  
Isa R. Akhmedov ◽  
Murad G. Kakagasanov ◽  
Zakir A. Aliev ◽  
Sergey P. Kramynin
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Sodium Perchlorate ◽  
First Order ◽  
Temperature Range ◽  
Temperature Dependences ◽  
Increasing Temperature

Structural and dynamic properties and molecular relaxation processes in crystalline sodium NaClO4 perchlorate in the temperature range from 300 K to 650 K were studied by Raman spectroscopy. The temperature dependences of the position of the maximum v (frequency), the width w and the intensity I of the spectral band, corresponding to the fully symmetric vibration v1(A) of the ClO4–1 perchlorate ion, in the spectral range from 933 cm–1 to 944 cm–1 were analyzed. The frequency v and intensity I decrease, and the width w increases with the increasing temperature. It is shown that these temperature dependences have certain features at a temperature of 460 K. With a further increase in temperature, the frequency v decreases more rapidly, the width w increases, and the intensity I decreases more intensively. In the temperature range from 460 K to the temperature Tstr = 581 K of the first order structural phase transition, we observe a deviation of the temperature dependence of the frequency and width from the linear dependences characteristic of lower temperatures. These deviations appear at a temperature of 460 K and increase with the increasing temperature and approaching the phase transition temperature. It has been established that in the crystalline sodium perchlorate NaClO4 a structural first-order phase transition is stretched. At the phase transition temperature (Tstr = 581 K), the width increases sharply, and the frequency decreases sharply, decreasing with a further increase in temperature. The existence of a pretransitional region in the studied crystalline sodium perchlorate NaClO4 was found. This pre-transition region occurs in the temperature range from 460 K to Tstr = 581 K.

SPECIFIC HEAT IN MONO-CRYSTAL YBCO: λ-LIKE ANOMALIES AT 90K AND 229K

1988 ◽  
Vol 02 (05) ◽  
pp. 1171-1183 ◽  
Author(s):  
K. Fossheim ◽  
O. M. Nes ◽  
T. Lægreid ◽  
C. N. W Darlington ◽  
D. A. O'Connor ◽  
...  
Keyword(s):  
Phase Transition ◽  
Specific Heat ◽  
High Precision ◽  
Order Phase Transition ◽  
Ybco Superconductor ◽  
Superconducting Transition ◽  
First Order ◽  
Temperature Range ◽  
First Order Phase Transition ◽  
First Order Phase

The specific heat, C p , has been measured with high precision in a mono-crystal of YBa 2 Cu 3 O 7−δ (YBCO) superconductor in the temperature range 55K-300K. The measurements provide data with a relative resolution Δ C p / C p of approximately 5 · 10−4. The main conclusions are: 1) Close to the superconducting transition the specific heat shows influence of fluctuations. 2) A reversible second order or weakly first order phase transition is found to occur at T o = 229 K .

Study on characteristics of schottky temperature detector based on metal/n-ZnO/n-Si structures

2020 ◽  
Vol 12 ◽  
Author(s):  
Fang Wang ◽  
Jingkai Wei ◽  
Caixia Guo ◽  
Tao Ma ◽  
Linqing Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Measurement ◽  
Temperature Response ◽  
Large Temperature ◽  
Mems Devices ◽  
Temperature Range ◽  
Response Characteristics ◽  
High Temperature Measurement ◽  
Temperature Detector ◽  
Schottky Structure

Background: At present, the main problems of Micro-Electro-Mechanical Systems (MEMS) temperature detector focus on the narrow range of temperature detection, difficulty of the high temperature measurement. Besides, MEMS devices have different response characteristics for various surrounding temperature in the petrochemical and metallurgy application fields with high-temperature and harsh conditions. To evaluate the performance stability of the hightemperature MEMS devices, the real-time temperature measurement is necessary. Objective: A schottky temperature detector based on the metal/n-ZnO/n-Si structures is designed to measure high temperature (523~873K) for the high-temperature MEMS devices with large temperature range. Method: By using the finite element method (FEM), three different work function metals (Cu, Ni and Pt) contact with the n-ZnO are investigated to realize Schottky. At room temperature (298K) and high temperature (523~873K), the current densities with various bias voltages (J-V) are studied. Results: The simulation results show that the high temperature response power consumption of three schottky detectors of Cu, Ni and Pt decreases successively, which are 1.16 mW, 63.63 μW and 0.14 μW. The response temperature sensitivities of 6.35 μA/K, 0.78 μA/K, and 2.29 nA/K are achieved. Conclusion: The Cu/n-ZnO/n-Si schottky structure could be used as a high temperature detector (523~873K) for the hightemperature MEMS devices. It has a large temperature range (350K) and a high response sensitivity is 6.35 μA/K. Compared with traditional devices, the Cu/n-ZnO/n-Si Schottky structure based temperature detector has a low energy consumption of 1.16 mW, which has potential applications in the high-temperature measurement of the MEMS devices.

scholarly journals Electric properties of olive oil under pressure

2021 ◽  
Author(s):  
L. T. Pawlicki ◽  
R. M. Siegoczyński ◽  
S. Ptasznik ◽  
K. Marszałek
Keyword(s):  
Molecular Structure ◽  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Olive Oil ◽  
Material Parameters ◽  
First Order ◽  
Long Time ◽  
Capacitive Reactance ◽  
First Order Phase

AbstractThe main purpose of the experiment was a thermodynamic research with use of the electric methods chosen. The substance examined was olive oil. The paper presents the resistance, capacitive reactance, relative permittivity and resistivity of olive. Compression was applied with two mean velocities up to 450 MPa. The results were shown as functions of pressure and time and depicted on the impedance phase diagram. The three first order phase transitions have been detected. All the changes in material parameters were observed during phase transitions. The material parameters measured turned out to be the much more sensitive long-time phase transition factors than temperature. The values of material parameters and their dependence on pressure and time were compared with the molecular structure, arrangement of molecules and interactions between them. Knowledge about olive oil parameters change with pressure and its phase transitions is very important for olive oil production and conservation.

scholarly journals Elastic Properties and Energy Loss Related to the Disorder–Order Ferroelectric Transitions in Multiferroic Metal–Organic Frameworks [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3]

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3125
Author(s):  
Zhiying Zhang ◽  
Hongliang Yu ◽  
Xin Shen ◽  
Lei Sun ◽  
Shumin Yue ◽  
...  
Keyword(s):  
Phase Transition ◽  
Energy Loss ◽  
Elastic Properties ◽  
Ferroelectric Phase ◽  
Loss Modulus ◽  
Structural Phase ◽  
Metal Organic Frameworks ◽  
First Order ◽  
Metal Organic ◽  
Elastic Anomalies

Elastic properties are important mechanical properties which are dependent on the structure, and the coupling of ferroelasticity with ferroelectricity and ferromagnetism is vital for the development of multiferroic metal–organic frameworks (MOFs). The elastic properties and energy loss related to the disorder–order ferroelectric transition in [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] were investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The DSC curves of [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] exhibited anomalies near 256 K and 264 K, respectively. The DMA results illustrated the minimum in the storage modulus and normalized storage modulus, and the maximum in the loss modulus, normalized loss modulus and loss factor near the ferroelectric transition temperatures of 256 K and 264 K, respectively. Much narrower peaks of loss modulus, normalized loss modulus and loss factor were observed in [(CH3)2NH2][Mg(HCOO)3] with the peak temperature independent of frequency, and the peak height was smaller at a higher frequency, indicating the features of first-order transition. Elastic anomalies and energy loss in [NH4][Mg(HCOO)3] near 256 K are due to the second-order paraelectric to ferroelectric phase transition triggered by the disorder–order transition of the ammonium cations and their displacement within the framework channels, accompanied by the structural phase transition from the non-polar hexagonal P6322 to polar hexagonal P63. Elastic anomalies and energy loss in [(CH3)2NH2][Mg(HCOO)3] near 264 K are due to the first-order paraelectric to ferroelectric phase transitions triggered by the disorder–order transitions of alkylammonium cations located in the framework cavities, accompanied by the structural phase transition from rhombohedral R3¯c to monoclinic Cc. The elastic anomalies in [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] showed strong coupling of ferroelasticity with ferroelectricity.

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

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