Using alloying to promote the subtle rhombohedral phase transition in vanadium

The compositions of Pb(Zr0.52Ti0.48)O3 doped with 1-6 mole% Nb content were prepared by a conventional mixed oxide technique. It was found that the phase formed depended on the dopant concentration. At lower concentration, the dominate phase was the tetragonal. With increasing Nb content the rhombohedral phase tended to increase. Furthermore, the Curie temperature (Tc) and dielectric constant decreased with increasing Nb concentration and the dielectric maximum peaks were broadened with more rhombohedral phase presence, causing the diffused ferroelectric-paraelectric phase transition. The impedance of the samples decreased with increasing temperature and it was also observed that the impedance increased with increasing Nb concentration.

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Second order elastic anomalies in barium titanate from orthorhombic to rhombohedral phase transition

Pramana ◽

10.1007/bf02847941 ◽

1994 ◽

Vol 43 (3) ◽

pp. 181-187 ◽

Cited By ~ 1

Author(s):

B Subramanyam

Keyword(s):

Phase Transition ◽

Barium Titanate ◽

Rhombohedral Phase ◽

Second Order ◽

Elastic Anomalies

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Structural and Magnetic Phase Transitions in ErFe2Hx Hydrides

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.152-153.33 ◽

2009 ◽

Vol 152-153 ◽

pp. 33-36 ◽

Cited By ~ 2

Author(s):

L.A. Shreder ◽

V.S. Gaviko ◽

N.V. Mushnikov ◽

P.B. Terent’ev

Keyword(s):

Phase Transition ◽

Hydrogen Content ◽

Magnetic Moments ◽

Exchange Interactions ◽

Rhombohedral Phase ◽

Small Variation ◽

Intermediate Stage ◽

Magnetic Phase Transitions ◽

Magnetic Studies ◽

The Difference

Temperature dependences of the lattice parameters, magnetization and magnetic susceptibility have been measured for the ErFe2Hx hydrides with different hydrogen content x and for the ErFe2D3.1 deuteride. For the samples with a hydrogen content of about 3.1, structural transition from the cubic to the rhombohedral phase has been observed in the temperature range 280 – 310 K. Small variation of hydrogen content does not shift the transition temperature, but influences the amount of the low-temperature rhombohedral phase. The temperature dependence of magnetization shows up an anomaly in the range of the phase transition, which is due to the difference in the magnitudes of magnetic moments and exchange interactions in two phases. Structural and magnetic studies point to a diffusion nature of the phase transition. Upon heating the samples in vacuum there takes place decomposition of the hydride. The hydride with x = 1.6 which forms at the intermediate stage of decomposition possesses an ordering temperature higher than that for the parent ErFe2 compound.

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Synthesis and characterization of nano-LaFeO3 powders by a softchemistry method and corresponding ceramics

10.31219/osf.io/8m4gf ◽

2019 ◽

Author(s):

Roberto Köferstein

Keyword(s):

Phase Transition ◽

Surface Area ◽

Rhombohedral Phase ◽

Phase Evolution ◽

High Specific Surface Area ◽

Coarse Grained ◽

Complexing Agent ◽

Porous Powder ◽

Enthalpy Changes ◽

Crystallite Sizes

The preparation of a nano-sized LaFeO3 powder by a soft-chemistry method usingstarch as complexing agent is described herein. Phase evolution and development of thespecific surface area during the decomposition process of (LaFe)-gels were monitored up to1000 °C. A phase-pure nano-sized LaFeO3 powder with a high specific surface area of 25.7m2/g and a crystallite size of 37 nm was obtained after calcining at 570 °C. TEMinvestigations reveal a porous powder with particles in the range of 20 to 60 nm. Calcinationsto 1000 °C result in crystallite sizes up to 166 nm. Dilatometric measurements of the sinteringbehaviour show that the beginning of shrinkage of pellets from the nano-sized powder is downshifted by more than 300 °C compared to coarse-grained mixed-oxide powder. The orthorhombic - rhombohedral phase transition was observed at 980 °C in DTAmeasurements for coarse-grained ceramic bodies. The enthalpy change (dH) during the phasetransition and the thermal expansion coefficient (adil) for ceramics was determined as 410 J/mol and 11.8×10-6 K-1, respectively. Whereas the enthalpy changes during the phase transition of the nano-sized LaFeO3 powders are £ 200 J/mol.

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