• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.806-814
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• 1992

The aim of this study was to investigate the change in compressive strength, freacture behavior and degradation of piezoelectric properties with compressive cyclic loading in Pb(Zr, Ti)O3 of tetragonal, morphotropic phase boundary and rhombohedral composition. The highest compressive strength was found in rhombohedral composition. After poling treatment the strength increased by 8.4% and 6.5% in tetragonal and morphotropic phase boundary compositions respectively while changed little in rhombohedral. The increase of compressive strength after poling treatment is believed to be due to the internal stress around grain boundary by domain alginment toward electric field direction in the microstructures having tetragonality and the occurrence of domain switching to the direction perpendicular to electrical field during fracture. Fracture mode relatively change from transgranular to intergranular was observed in the large grain sized tetragonal and morphotropic phase boundary compositions before and after poling but the transgranular fracture mode always remained in the rhombohedral composition. From the X-ray diffractometer analysis the domains parallel to the electric field direction is known to undergo rearrangement during the cyclic loading into random direction that is responsible for the degradation of piezoelectric property.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.915-921
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• 1995

The morphotropic phase boundary and phase transitions of the solid solutiion system, (1-x)(Na1/2Bi1/2)TiO3-PbTiO3＋xPbTiO3 were studied by investigating changes in crystal structure, variations in permittivity with temperature, and calorimetric behavior. It was observed that the morphotropic phase boundary (MPB) of this solid solutiion system was at near 14 mol% of PbTiO3. Compositions containing less than 10mol% PbTiO3 (x<0.1) exhibited a phase transition, i.e. ferroelectric rhombohedrallongrightarrowparaelectric paraelectric cubic, with increasing temperature. Composition containing more than 14 mol% PbTiO3 (x 0.14) showed a phase transition from ferroelectric tetragonal to paraelectric cubic. In the composition range of 0.1$\varepsilon$ (T) curve, which coincided with a phase transition from ferroelectric rhombohedral to an intermediate phase, was also found.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1027-1033
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• 1990

In order to identify the origin of phase coexistence at morphotropic tetragonal and rhombohedral boundary in PZT ceramics, the effect of chemical inhomogeneity on phase coexistence region was investigated. Two kinds of PZT ceramics with different chemical homogeneity were prepared by conventional solid state reaction and co-precipitation method. There was coexistence of tetragonal and rhombohedral phase over a wide composition range in PZT ceramics calcined by solid state reaction, and there was also phase coexistence of which region was reduced considerably in sintered samples. And phase coexistence region was not observed in co-precipitated PZT ceramics(within 1 mole%). Therefore compositional fluctuation is considered to be major origin of the phase coexistence at morphotropic phae boundary in PZT ceramics.

• Journal of the Korean Ceramic Society
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• v.30 no.10
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• pp.859-865
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• 1993

Morphotropic tetragonal and rhombohederal phase boundary(MPB) in PZT system was calculated and the effect of mechanical stress and electric field on the MPB was examined using phenomenological thermodynamic theory proposed by Devonshire. Mechanical stress and electric field was calculated to change free energies of phases and shift MPB. The stable composition range of the phase, of which spontaneous strain and spontaneous polarization aligned to the direction of tensile stress or electirc field, was expanded.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.253-259
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• 2012

In this study, crystal structural changes and dielectric properties of $(1-x)Pb(Yb_{1/2}Nb_{1/2})O_3-xPbTiO_3$ ((1-x)PYN-xPT) solid solutions were measured and analyzed with respect to the $PbTiO_3$ (PT) contents ($0.40{\leq}x{\leq}0.60$). From X-ray diffraction (XRD) measurements, (1-x)PYN-xPT solid solutions showed changes of the crystal structure from pseudocubic ($0.40{\leq}x{\leq}0.44$) to tetragonal ($0.52{\leq}x{\leq}0.60$) on increasing PT contents and exhibited the coexistence of pseudocubic and tetragonal phase near the morphotropic phase boundary (MPB) composition ($0.46{\leq}x{\leq}0.50$). The dielectric constant showed a maximum value at x = 0.46 and the maximum values in (1-x)PYN-xPT decreased with higher PT contents. The phase transition temperatures of (1-x)PYN-xPT solid solutions increased over the whole composition ranges tested ($0.40{\leq}x{\leq}0.60$).

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.68-72
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• 2007

Optimum compositions for piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics were investigated in the range of $x=0{\sim}0.1$ covering rhombohedral to tetragonal phase regions. No impurity phases other than a perovskite phase were found and the grain size decreased with increasing x. A two-phase coexisting morphotropic phase area rather than boundary dividing rhombohedral and tetragonal phase regions appeared to exist at $x=0.05{\sim}0.08$. As for piezoelectric properties within morphotropic phase compositions, the piezoelectric constant ($d_{33}$) and the electromechanical coupling factor ($K_p$) showed peak values at x=0.065, 192 pC/N and 34%, respectively, indicating x=0.065 as an optimum composition for piezoelectric $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.148-155
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• 2008

Dielectric and pyroelectric properties of relaxor ferroelectric in the PMN-PT solid solution series have been investigated. Features of the diffuse phase transition in PMN-PT system, typical relaxor ferroelectric materials, were studied as a function of temperature and frequency. The transition temperature of the ceramics with PT$\sim$0.325 did not depend on the measuring frequency. This can best realized in a relatively random environment that apparently is provided by PMN-rich complex perovskites, including those containing Pb. The composition with PT>0.35 show the characteristics of a normal single phase ferroelectric material. Thus the studies revealed that the morphotropic phase boundary in the PMN-PT system is in the vicinity of PT$\sim$0.3 and it has a small curvature and as a result the compositions near the morphotropic phase boundary show two phase transitions, rhombohedral$\rightarrow$tetragonal$\rightarrow$cubic, when the samples are heated up to higher temperature. The best optimum compositions are observed near the morphotropic phase boundary.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1989.06a
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• pp.70-73
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• 1989

(1-x-y)Pb($Zn_{1/3}Nb_{2/3})O_3-Ba(Zn_{1/3}Nb_{2/3})O_3-PbTiO_3(0.12{\leq}x{\leq}0.21, 0.24{\leq}y{\leq}0.33$) ternary compound ceramics were fabricated by the mixed oxide method. The sintering temperature and time were 1050 [$^{\circ}C$], 2[hr]. Morphotropic phase boundary region was chosen for the composition. 0.55 PZN-0.21 BZN-0.24 PT specimen had the highest value of relative dielectric constants, 5353. The curie temperature of specimens were increased linearly with PT content. Near the morphotropic phase boundary, electro-mechanical coupoling factor and mechanical quality factor of the specimens had the highest values.

• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.413-417
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• 2003

The effect of 0-0.7 ㏖% addition of $Cr_2$$O_3$on the dielectric, pyroelectric, and piezoelectric properties were studied in the (Mg$0.7Pb_{1}$$3/Nb_{2}$3/)$O_3$-$0.3PbTiO_3$(0.7PMN-0.3PT) ceramics with composition near the morphotropic phase boundary. The dielectric constant and loss of the ceramics samples were measured as a function of temperature at various frequencies (0.1-100 KHz). The pyroelectric coefficient was measured by using the Byer-Roundy method as a function of temperature. Dielectric, pyroelectric, and piezoelectric constant achieved the maximum values of 0.4 ㏖% $Cr_2$$O_3$The transition temperature is continuously shifted to lower temperature with an increase of a small amount of $Cr_2$$O_3$.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.53-59
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• 1992

Piezolectric ceramics of Pb(Zr, Ti)O3 system were fabricated and used for shear type accelerometer. Among compositions studied, La+3 and Nb+5 doped composition showed the highest d15, and K15 and the morphotropic phase boundary (M.P.B) was shifted toward rhombohedral site.