Search results for "Titanate"
showing 10 items of 131 documents
Low and Infra-Low Frequency Measurements in Lead Titanate Solid Solutions
2006
The study of PSN-PT ferroelectric relaxor ceramics exhibiting extreme values of some physical parameters near the morphotropic phase boundary is reported. The results are discussed to account for the relaxor properties related to defects and disordering of the PSN-PT system.
Structure and Properties of Novel Pb(B’1/2Nb1/2)O3-PbTiO3 Binary Systems with High Piezoelectric Coupling
2000
The (l-x)Pb(Lu1/2Nb1/2)O3-xPbTiO3 (PLuNT) and (l-x)Pb(Er1/2Nb1/2)O3-xPbTiO3 (PErNT) binary systems have been originally synthesized. Pure lutecium niobate (PLuN) (x = 0) has a pronounced long-range order in the B-sublattice and an antiferroelectric to paraelectric phase transition at ~258°C. The phase structure of the PLuNT system, at room temperature, changes from a pseudomonoclinic (psd-M, space group Bmm2) to tetragonal (T, space group P4mm). The pseudomonoclinic phase extends over the 0 ≤ x ≤ 0.38 interval within which the monoclinic angle β proceeds a minimum near to 90° at x≅0.2. The morphotropic region covers over the interval x = 0.38–0.49, the concentration ratio psd-M:T≅l (the mor…
Crystal structure transformations induced by surface stresses in BaTiO3and BaTiO3@SiO2nanoparticles and ceramics
2015
International audience; Lattice structure transformations in nanopowders of ferroelectric BaTiO3 and BaTiO3@SiO2 core-shell nanostructured ceramics were studied by nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) at the temperatures 120–450 K and particle size of 300 and 500 nm. NMR spectra of all studied samples in the paraelectric phase are identical to the spectra in bulk material indicating their perfect perovskite structure without visible influence of particle surface. However, we have found that surface of particles essentially influence the ferroelectric phase transitions detected by both NMR and EPR techniques. The strongest changes as compared to bulk mat…
Study of the spontaneous relaxor to normal ferroelectric phase transition in la-doped lead titanate
2000
Abstract Highly lanthanum doped lead titanate ceramics exhibit relaxor properties and undergo on cooling a subsequent spontaneous macroscopic phase transition. The dielectric response is strongly affected by chemical (copper) doping and is found to become independent of the applied ac field for temperatures lower than the phase transition one.
Electroluminescence of (Pb0.91La0.09)(Zr0.65Ti0.35)O3 relaxor ceramics
2013
Abstract Lanthanum doped lead zirconate titanate (PLZT) relaxor ceramics with (Pb 0.91 La 0.09 )(Zr 0.65 Ti 0.35 )O 3 composition exhibit a repolarization induced by electroluminescence (EL) with a pronounced discrete character of emission. It is established that this behavior is related to the reorientation of nanodimensional polar regions in a strong pulsed electric field in the vicinity of a smeared phase transition. The time and temperature dependences of the EL intensity are studied.
Thermo-Optical Investigation of Sodium-Bismuth Titanate Single Crystal and PLZT Ceramics
2005
Thermal lensing in relaxor type ferroelectrics as a function of temperature has been investigated by using pulse/probe method. Enhanced thermo-optical (TO) properties had been observed in 3d elements (Cu, Co) doped PLZT ceramics and in sodium-bismuth titanate single crystals near phase transitions (PT). Comparison of TO signals for several doped PLZT materials reveals that 0.5 wt.% Cu doping is responsible for improved thermal lensing parameters interpreted by optimal light absorption, heat transfer and possible PT adjustment. TO experiments in sodium-bismuth titanate single crystals ([001] cut) show enhancement of TO properties in the region of PT and coexisting phases (rhombohedral and te…
Microstructure, calorimetric and dielectric investigation of hafnium doped barium titanate ceramics
2013
Ferroelectric properties of BaTi1− x Hf x O3 ceramics with Hf content x = 0, 0.001, and 0.025 were examined. It was found that the substitution of Hf4+ for Ti4+ in BaTiO3 resulted in shifting the two low-temperature transitions (T 1, T 2) of the investigated samples to higher temperatures and decreasing the tetragonal-cubic phase transition temperature (T c). This is a well-known pinching effect. Thermal parameters of the transitions, such as the enthalpy ΔH and the entropy ΔS, were also estimated and discussed.
Specifics of polarisation switching in PbNi1/3Nb2/3O3–PbTiO3–PbZrO3 ferroelectric ceramics
2004
Abstract The growing interest in disordered relaxor ferroelectrics is due to unusual properties mainly related to the existence of broad phase transitions characteristic to the systems. The effects of bias field on the dielectric response and polarisation switching are studied in the 0.5 PbNi 1/3 Nb 2/3 O 3 – x PbTiO 3 –(0.5− x ) PbZrO 3 system at different PbTiO 3 :PbZrO 3 ratio. Thermal behaviour of normalised remnant polarisation P r / P max of compositions with content of lead titanate x =0.33 and x =0.35 at frequency 0.1 Hz and different values of field E o are measured. Results of measured polarisation and depolarisation currents are compared with characteristics of polarisation switc…
Influence on the phase transitions of barium titanate of the manganese valency, introduced as a substituant in the titanium site
1991
Abstract A small amount of manganese introduced in BaTiO3 modifies strongly the vibrational and electronic properties of the pure compound. Dielectric response and EPR measurements are reported in order to study the influence of the manganese valency on the ferroelectric-paraelectric phase transition.
Thermodynamic considerations of the grain size dependency of material properties
1994
Phase transitions which depend on grain size induce very interesting properties in materials such as zirconia or barium titanate. A new and rigorous thermodynamic treatment of this type of phase transition is proposed with consideration of the surface phenomena. An interpretation is given of the observed differences when the material—particularly BaTiO3—under consideration is a fine grain powder or is a fine grain ceramic.