PbTiO3 Content Research Articles

PbTiO3‐PbO‐B2O3 Glass‐Ceramics by a Sol‐Gel Process

PbTiO3 (PT)‐PbO‐B2O3 glass‐ceramics were produced by a sol‐gel process. Achievement of high PT content at levels unattainable by conventional glass‐ceramics preparation methods was semiquantitatively shown. PT content was similar to the designed PT volume fraction and seemed rather unaffected by the composition of the glassforming component at a calcination temperature of 700°C. A higher ratio of PbO to B2O3 in the glassforming component resulted in a low PT crystallization temperature, <500°C. PT crystals 1‐2 μm in size were obtained at calcination temperatures >600°C.

Phase relations in the system of (Na1/2Bi1/2)TiO3–PbTiO3. II. Dielectric property

The region of the phase diagram in the system (Na1/2Bi1/2)1−xPbxTiO3 from x=0 to 0.2 was established using dielectric measurements along with the phase diagram established in part I of this work. The diffuse phase transition behavior of solid solutions with low PbTiO3 content was also investigated. When x is lower than xrc (composition at which rhombohedral↔cubic transition exists) the rhombohedral↔tetragonal transition accompanied an anomaly in the ε(T) curve which shows an abrupt jump, followed by diffuse behavior of the ε(T) curve during heating. When xrc<x<xMPB (rhombohedral–tetragonal morphotropic phase boundary composition at room temperature) the rhombohedral↔tetragonal transition was a normal ferroelectric-to-ferroelectric transition but the tetragonal↔cubic transition showed diffuse behavior following the abrupt jump in the ε(T) curve. The temperature of the structural change coincided with the abrupt jump in ε(T) curve. Normal ferroelectric phase transition from ferroelectric tetragonal to paraelectric cubic was found when x≳xMPB. It was found that the temperature range of the reported antiferroelectric phase would follow that of the diffuse transition range regardless of the crystal symmetry. It can be said that the antiferroelectric phase of (Na1/2Bi1/2)1−xPbxTiO3 is strongly connected with the diffuse transition behavior during ferroelectric phase transition.

Low‐Temperature Observation of Relaxor Ferroelectric Domains in Lead Zinc Niobate

Domain reorientation in single crystals of lead zinc niobatelead titanate solid solutions was examined, because the reorientation contributes to the electrically controlled change of shape and change of response in piezoelectric transducers and actuators. An optical microscope technique was used to explore the buildup of macropolar domains from micropolar regions in relaxor compositions. Poorly defined “ambiguous” spindlelike domains changed to distinct lamellar domains as PbTiO3 content was increased. The domain walls in Pb(Zn1/3Nb2/3)O3‐rich samples moved with a wavelike motion. The motion ceased or “froze‐in” below –130° and –30°C for field‐biased and nonbiased samples, respectively. The domains were observed at various temperatures from 300° to –185°C and electric fields up to ±10kV/cm.

Dielectric and Piezoelectric Properties of Pb(Yb1/2Nb1/2)O3-PbTiO3 Solid Solution System

Solid solutions of (1- x)Pb(Yb1/2Nb1/2)O3-( x)PbTiO3x=0 to 0.8 were investigated from the viewpoint of dielectric and piezoelectric properties. With increasing PbTiO3 content (x), phases at room temperature continuously changed from antiferroelectric (x=0), ferroelectric (x=0.1 to 0.15), relaxor (x=0.2 to 0.49), and again to ferroelectric (x>0.49), where crystal structures of all these phases were perovskite. Sintering temperature was lowered to around 950° C in the relaxor phase (x=0.2 to 0.49). Piezoelectric constants exhibited a maximum at x=0.49 to 0.50 near the morphotropic phase boundary (x=0.49). In the sample with x=0.50, Curie point was 349° C, and remanent polarization and coercive field were 32.8 µ C/cm2 and 2.75 kV/mm, respectively. Also, electromechanical coupling factors for planar (k p) and thickness (k t) modes were 0.527 and 0.436, respectively.

Phase Transition and Ferroelectric Characteristics of Pb[(Mg1/3Nb2/3)1‐xTix]O3 Ceramics Modified with La(Mg2/3Nb1/3)O3

The effects of 0–5 mol% addition of La(Mg2/3Nb1/3)O3 (LMN) on the phase transition and ferroelectric behaviors of Pb[(Mg1/3Nb2/3)1‐xTix]O3 (PMNT) ceramics with compositions near the morphotropic phase boundary (MPB) were studied. An evolution of structure from rhombohedral to tetragonal was found with increasing PbTiO3 (PT) content across the MPB (at ∼32.5 mol% PT), and a coexistence of both rhombohedral and tetragonal phases was also found at the MPB. The dual‐phase field extended toward the lower PT content side of the MPB, and, moreover, the rhombohedrality or tetragonality was reduced, especially for the compositions near the MPB, by the addition of La in PMNT. The ferroelectric transition was found to change from normal to diffuse as the La content increased and the compositions became more rhombohedral. In accordance with the structural evolution, the change of remanent polarization (Pr) and coercive field (Ec) also became gradually indistinct, and both Pr and Ec were reduced. For compositions near the MPB, both PMNT and La‐modified PMNT had a similar electromechanical factor (kp) in a range around 0.55–0.60, but the mechanical quality factor (Qm) was significantly reduced for the La‐modified PMNT. The piezoelectric coefficient (d33), however, was largely improved with increasing La content in PMNT of compositions at MPB. A high value of d33∼ 815 pC/N was obtained for the 5‐mol%‐La‐modified ceramics, but it was associated with a low value of Qm.

Phase diagrams of the system of solid solutions Pb1−x(Li½La½)x(Zr1-yTiy)O3O3in the vicinity of the FE-AFE phase boundary

Abstract A study of the influence of the substitution of (Li½La½)+2 for Pb+2 ions on the relative stability of the FE and AFE phases in PZT solid solutions is reported. The corresponding part of the “Ti-contenttemperature’ phase diagrams are constructed for the substitution of (Li½La½)+2 for Pb+2. The region of the AFE phase stability of PZT expands towards higher content of PbTiO3 in the solid solutions. Regions of induced FE states have been found between stable FE and AFE phases.

The properties of xPbTiO‐ (0.9 — x) PbZrO‐ 0.1 PbW0.5Cd0.5O3 solutions in the region of coexistence of tetragonal and rhombohedral phases

AbstractThe changes of the dielectric permittivity η, dielectric loss tg δ, piezoelectric coefficient d33, pyroelectric coefficient p, remanent polarization Pr and reorientation processes of polarization in dependence on percent content of PbTiO3 in the xPbTiO3−(0.9 — x) PbZrO3− 0.1 PbW0.5Cd0.5O3 solid solutions in the phase coexistence region (PCR) wree investigated. It was pointed out that the characteristics of mentioned parameters possess singularities in this region. The values of average Curie temperature obtained from structural, dielectric and pyroelectric measurements were compared. Presented results let us connect dielectric properties of studied solid solutions with their structure.

Piezoelectric Properties and Phase Relations of Pb(Mg1/3Nb2/3)O3‐PbTiO3−PbZrO3 Ceramics with Barium or Strontium Substitutions

When a small amount of Ba or Sr is substituted for Pb in Pb(Mg1/3 Nb2/3)O3‐PbTiO3‐Pb2rO3, the morphotropic boundary and the compositions which show the highest planar coupling coefficient and dielectric constant shift slightly toward the decreasing PbTiO3 content. The tetragonality of Pb(Mg1/3Nb2/3)O3‐PbTiO3 and Pb(Mg1/2 Nb2/3)‐O3‐PbTiO3‐PbZrO3 ceramics decreased with increasing Ba or Sr content. The lattice parameter (α axis) in the rhombohedral or pseudocubic phase increased with the increase of Ba but decreased with the increase of Sr substitution. Although the Curie temperature was lowered with the increase of Ba or Sr, the dielectric constants of the ceramics were increased. The dielectric and piezoelectric properties of the ternary compositions near the morphotropic boundary were improved through selection of sub‐stituent and base composition. A planar coupling coefficient of 0.66 and a low Young's modulus were obtained with substitution of 5 mole % Ba. A dielectric constant greater than 3500 and a planar coupling of 0.63 can be obtained by substituting 5 mole % Sr.