Edward F. Alberta

Elastic, piezoelectric, and dielectric characterization of modified BiScO/sub 3/-PbTiO/sub 3/ ceramics

The perovskite solid solution system (1-x)BiScO/sub 3/-(x)PbTiO/sub 3/ represents an interesting new family of high-temperature piezoelectric materials. Compositions near the morphotropic phase boundary (x /spl sim/ 0.64) have been reported to have high Curie temperatures (T/sub c/ > 450/spl deg/C) and good piezoelectric coefficients (d/sub 33/ /spl sim/ 460 pC/N). In this work, manganese additions were used to improve the high-temperature electrical resistivity and RC time constant of compositions near the morphotropic phase boundary. The addition of manganese was found to shift T/sub C/ to slightly lower temperatures (442/spl deg/C and 456/spl deg/C for x = 0.64 and x = 0.66, respectively). The piezoelectric activities of the modified materials were found to be reduced slightly due to the hardening effect of manganese; however, the temperature stability and resistivity of the modified materials were significantly enhanced. In this paper we present, for the first time, a complete set of materials constants, including the elastic (s/sub ij/, c/sub ij/), piezoelectric (d/sub ij/, e/sub ij/, g/sub ij/, h/sub ij/), dielectric (/spl epsi//sub ij/, /spl beta//sub ij/), and electromechanical (k/sub ij/) coefficients and compare them to both unmodified 0.36BiScO/sub 3/-0.64PbTiO/sub 3/ and PZT5A ceramics.

Manganese-modified BiScO3–PbTiO3 piezoelectric ceramic for high-temperature shear mode sensor

The bismuth-based perovskite solid solution (100−x)BiScO3−xPbTiO3 (BSPT) was investigated for use at temperatures up to 400°C and above. The high-temperature resistivity, together with dielectric and piezoelectric behaviors of the shear mode for manganese-modified BSPT ceramics near the morphotropic phase boundary composition were studied. The resistivity and time constant were found to be 3×107Ωcm and 0.08s, respectively, at 450°C for modified BSPT66. The dielectric constant Κ11T and dielectric loss were found to be 1112 and 1%, respectively, at room temperature, showing a Curie temperature at 468°C. The electromechanical coupling factor k15 was calculated to be 61%, staying nearly constant up to 440°C, expanding the temperature usage range significantly. The properties indicate that the modified BSPT66 material is a promising candidate for high-temperature shear sensor applications.

High Curie temperature perovskite BiInO3-PbTiO3 ceramics

The extent of BiInO 3 substitution in the perovskite system x BiInO 3 –(1 - x )PbTiO 3 and the corresponding raise in the Curie temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion ( c / a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582 °C. Phase-pure tetragonal perovskite was obtained for x ⩽ 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Sol-gel fabrication resulted in nano-sized tetragonal or pseudo-cubic perovskite particles, which after two-step firing, resulted in a tetragonal perovskite microstructure at as high as ( x = 0.20) 98.1% of TD.

Nonlinear dielectric ceramics and their applications to capacitors and tunable dielectrics

Nonlinear ceramics that provide the basis for high-energy-density and high-temperature capacitors, as well as tunable microwave dielectrics, and their applications are discussed in this article.

Low-temperature properties of lead nickel-niobate ceramics

Abstract Single-phase perovskite ceramics of Pb(Ni 1/3 Nb 2/3 )O 3 (PNN) are prepared by the columbite precursor method. Dielectric studies show that ceramic Pb(Ni 1/3 Nb 2/3 )O 3 is a typical relaxor ferroelectric with properties similar to those of its single-crystals. Low-temperature pyroelectric properties and electromechanical coupling coefficients suggest PNN to be an attractive material for low-temperature applications.

Preparation of phase-pure perovskite lead indium niobate ceramics

Abstract To date, attempts to fabricate single phase perovskite Pb(InNb) 1 2 O3 (PIN) ceramics have met with only limited success. This paper describes a processing method for synthesizing phase-pure PIN ceramics using the wolframite precursor method. Dielectric properties of these undoped ceramics seem to be superior to those reported by previous investigators and are comparable to the single crystal properties of lead indium niobate.

Piezoelectric and dielectric properties of transparent Pb(Ni1/3Nb2/3) 1-x-yZrxTiyO3 ceramics prepared by hot isostatic pressing

Abstract The dielectric, pyroelectric, piezoelectric and optical properties of transparent Pb(Ni 1–3 Nb 2/3 ) 1− x − y Zr x Ti y O 3 (PNNZT) ceramics have been investigated. Hot isostatic pressing was used to achieve uniformly transparent ceramics with optical transmittance of more than 5% at 633 nm. The room temperature dielectric constant of 4200 and a loss of ∼0.025 were measured on these samples. Large electromechanical coupling factors, k p =69%, k 31 =43%, k t =56%, and k 33 ∼80%, and large pyroelectric coefficients, 0.2075 μC/cm 2 K at room temperature and 2.3819 μC/cm 2 K at 129°C, were observed for poled ceramics. Transparent PNNZT ceramics could be promising candidates for many applications such as electrooptics, pyrooptics, and electromechanical transducers/sensors.

Novel BST: MgTiO3 composites for frequency agile applications

The (Ba 1 m x Sr x )TiO 3 (BST) system is well known for its high response of the dielectric constant to an applied electric field. However, the large dielectric constants found in this system limit its usefulness at microwave frequencies. A number of groups have used composite structures to dilute the dielectric constant and suppress the dielectric loss of BST for microwave applications. Typically, the low dielectric constant material MgO has been used as the secondary phase in the composites. In this work, we report on the dielectric properties of BST composites using the microwave dielectric MgTiO 3 . Room temperature dielectric constants of <400 (measured at 1 kHz), and dielectric tunabilities of ∼36% (at 20 kV/cm) have been achieved for the BST:MT composites. Due to the superior quality of these composite ceramics, large electrical breakdown fields in excess of 100 kV/cm are possible. High-field measurements indicate that the dielectric tunability of BST:MgTiO 3 composites can be as high as 70% at 80 kV/cm.

Investigation of the lead indium niobate-lead magnesium niobate solid solution

Abstract This paper describes the first study on processing and electrical properties of ceramics in the ( x )Pb(In 1/2 Nb 1/2 )O 3 :(1− x )Pb(Mg 1/3 Nb 2/3 )O 3 [PIMN( x /100− x )] solid solution system with x =50 mol%. Pellets were sintered at 1100°C resulting in phase-pure perovskite ceramics with 98% theoretical density. These ceramics displayed typical relaxor ferroelectric behavior with a maximum dielectric constant of 8056 at 26°C. A slight polarization hysteresis was observed at 25°C. A maximum induced polarization of 23.95 μC/cm 2 and remanent polarization of 1.2 μC/cm 2 at the peak field level of 48 kV/cm was measured. The strain and electrostriction coefficient were measured, the values were in the range of x 33 =8.12×10 −4 and Q 33 =1.42×10 −2 m 4 /C 2 , respectively. The low hysteresis in x 33 and low values of P r make this solid solution attractive for further study.

Some comments on the morphotropic phase boundary and property diagrams in ferroelectric relaxor systems

Abstract Morphotropic phase boundary compositions are very attractive for designing various electronic sensors, capacitors and piezoelectric transducers. Therefore, highly reliable and accurate structure–property diagrams in relaxor ferroelectric systems are desirable. This paper comments on, and draws attention to, certain important points which researchers should take into consideration while drawing structure–property diagrams.