James V. Biggers

Simplified fabrication of PZT/polymer composites

Abstract Skinner, et al. prepared PZT/polymer composites using the coral replamine process. The composites were found to have, for certain applications, greatly improved electromechanical and physical properties over those of conventional piezoelectric materials. However, the coral replamine process requires natural coral from the ocean as the starting replica material, making this process industrially unfavorable. This paper discussed PZT/polymer composites electromechanically and physically comparable to the Skinner replamine composites. Fabrication is simplified by the use of a compacted mixture of volatilizable plastic spheres and PZT powder, which when sintered yields a piezoelectric with a density of less than 2.9 g/cm 3 , a permittivity of ∼120 and a d 33 of 180×10 −12 C/N. The improved connectivity increases d h (hydrostatic) from ∼35×10 −12 C/N (solid PZT) to 100×10 −12 C/N.

Fabrication and electrical properties of grain oriented Bi4Ti3O12 ceramics

Abstract A fabrication process has been developed by which Bi4Ti3O12 can be made in ceramic form with high densities (92% theoretical) and substantial grain orientations (>95%). The process consists of molten salt synthesis of platelets of Bi4Ti3O12, tape casting, and conventional sintering. Electrical measurements have verified the high degree of grain orientation obtained in these ceramics. Permittivities in the a-b oriented direction (along the plane of the tape) and the c oriented direction (perpendicular to the plane of the tape) at 100 KHz are 153 ± 5 and 118 ± 5, respectively. Conductivities at 1 KHz and 500°C in the a-b and c oriented directions are 6.3 × 10−2 and 4.2 × 10−3 (ohm-m)−1, respectively. The c oriented direction was poled to a d33 of 5 × 10−12 C/N with the application of a DC field. The a-b oriented direction was poled to a d33 of 10 × 10−12 C/N with the application of a pulsed field on cooling through the transition.

Piezoelectric properties of internally electroded PZT multilayers

Abstract Platinum internal electrodes have been introduced into PZT compositions in a multilayer configuration by a conventional tape casting process. Electrical property data for the devices suggest that the piezoelectric coefficients of the multilayer configuration are approximately 20% lower than those of similar plain PZT devices. However, the applied voltage/displacement ratio is much lower in the multilayer compared to the plain devices. Resonant properties are almost unaffected by the presence of internal electrodes for hard PZT compositions. Piezoelectric transformers with multilayer primaries show improved transformer ratios compared to conventional devices.

Dielectric aging in the plzt system

The aging rates of K and tan δ were determined for some ferroelectric and antiferroelectric PLZT compositions as a function of frequency and DC bias. The aging reached a maximum at the FER-AF0 boundary. The antiferroelectric compositions exhibited aging in both K and tan δ. PbZrO3 has a K aging rate of 2.4% per decade. All aging rates were found to decrease with increasing frequency. DC bias increased the aging rate of K for the ferroelectrics and had little effect on the antiferroelectrics.

Electromechanical behavior of antiferroelectric-ferroelectric multilayer PZT based composites

Using a tape casting process, lamellar heterogeneous devices comprised of layers of a commercial soft ferroelectric (modified PZT) and an antiferroelectric (modified PZSnT) were produced. Such devices were found to behave in a similar way to that of a transpolarizer and to effectively stabilize the polarization in the soft material under high field cycling conditions.

Preparation and reactivity of lead zirconate-titanate solid solutions produced by precipitation from aqueous solutions

Abstract A process for preparation of PZT by precipitation from butoxide precursors is described. The reactivity of the powders during low temperature firing (calcining) has been determined using weight loss, x-ray diffraction, and DTA-TGA techniques.

CaLa 2 S 4 : Ceramic Window Material For The 8 to 14 μm Region

CaLa2S4 is a member of the family of ternary sulfides. It has the cubic Th3P4 structure, space group I-43d, with both cations on equivalent 8-coordinated sites. Powders prepared by firing oxides and carbonates in flowing H2S can be processed by a combination of hot-pressing and hot-isostatic pressing into sulfide ceramics with good infrared transmission. The vibrational absorption edge is at 17 μm. The materials are resistant to attack by water. The microhardness of the nearly 100% dense ceramics is 600 kg/mm2. Optical transmission of 55% (including reflection losses) at 14 μm has been achieved, but optical quality is extremely sensitive to processing conditions. Absorption and scattering are produced by residual pores, by second phase impurities on grain boundaries, by oxidation products such as sulfate and thiosulfate, and electronic defects arising from non-stoichiometry.

Temperature compensated composite resonator

Abstract A composite resonator was designed and fabricated by the use of a multilayer tape casting technique. A multilayer composite composed of Pb3 MgNb2O9 and 0.8 Pb3MgNb2O9 + 0.2 PbTiO3 (chosen for their nearly compensating resonant temperature coefficients) was found to have improved temperature stability. Resonant frequency changes of < 60 ppm/°C were found over a temperature range of - 10°C to 80°C.

Resonance behavior of internally electroded PZT devices

Abstract Preparation and resonant properties of hard and soft internally electroded PZT bars are described. The presence of cofired platinum internal electrodes is shown to have little effect on the resonance behavior of hard PZT. Piezoelectric transformers having internally electroded primaries and secondaries are compared with conventional devices and show improved transformer ratio and power handling capability.

Piezoelectric properties of Pb5Ge3O11 bonded PZT composites

Abstract Pb 5 Ge 3 O 11 was used to form dense piezoelectric composites with PZT at temperatures below 1000°C. The composite material demonstrated that the ferroelectric component may be stabilized against depoling by an insulating grain boundary phase. Composites prepared using 30% Pb 5 Ge 3 O 11 almost fully stabilized the polarization against reverse field of 40 kv/cm, with d 33 = 65 × 10 −12 m/v and k = 470.