Showing papers by "L. E. Cross published in 1982"
TL;DR: In this article, a glass-ceramics of composition Ba2Ge2TiO8 with oriented crystallites were prepared by crystallizing the glasses in a temperature gradient, and the degree of preferred orientation of the crystallites as a function of depth was studied.
Abstract: Glass-ceramics of composition Ba2Ge2TiO8 with oriented crystallites were prepared by crystallizing the glasses in a temperature gradient. The degree of preferred orientation of the crystallites as a function of depth was studied. Piezoelectric resonance properties of both the glass-ceramics and the single crystals were studied. The piezoelectricd33 coefficient, the frequency constants and the electromechanical coupling coefficients of the glass-ceramic were comparable to the single-crystal values.
33 citations
TL;DR: In this paper, a single domain single crystal of Bi4Ti3O12 has been measured at room temperature using appropriate crystal cuts on a Berlincourtd33 meter.
Abstract: The piezoelectric constantsd
11,d
22 andd
33 for a single domain single crystal of Bi4Ti3O12 have been measured at room temperature using appropriate crystal cuts on a Berlincourtd
33 meter. From the known temperature dependence of the spontaneous polarization, lattice strain and dielectric permittivity, the equivalent piezoelectric constants have been calculated assuming a simple proper ferroelectric in which,P
s, is the order parameter. Constants in the plane of the perovskite-like sheets in the Bi4Ti3O12 structure (d
11,d
22) show good agreement with experimental values. The calculated value of the constantd
33 is more than an order of magnitude larger than the experimentally-measured value and gives clear indication of the “indirect” coupling to the strain in the tetrad axial direction and the need for a more sophisticated phenomenology.
22 citations
TL;DR: In this article, the spontaneous polarization was found to be 0.40 C/m2°C and the Curie transition was 350°C as determined from the temperature dependence of the dielectric constants.
Abstract: A ferroelectric tungsten bronze single crystal of Pb0.33Ba0.70Nb2O6 was grown from a melt using the Czochralski technique. The crystal belongs to the tetragonal point group 4mm with the spontaneous polarization parallel to the ‘c’ axis. The room temperature lattice parameters were a = 12.50 A and c = 3.995 A. The spontaneous polarization was found to be 0.40 C/m2°C. The Curie transition was 350°C as determined from the temperature dependence of the dielectric constants. The pyroelectric properties were found to be typical of other tetragonal ferroelectric bronzes. Dielectric constant ϵ11 and piezoelectric constant d15 show a strong enhancement from the approach of the tetragonal:orthorhombic morphotropic phase boundary and it is clear that crystals with composition in the tetragonal phase field closer to this boundary will be of major interest for piezoelectric and electro-optic applications.
15 citations
TL;DR: In this paper, glass ceramics in the system Li2O•SiO2•B2O3 with oriented crystallites were prepared by crystallizing the glasses in a temperature gradient.
Abstract: Glass ceramics in the system Li2O‐SiO2‐B2O3 with oriented crystallites were prepared by crystallizing the glasses in a temperature gradient. Piezoelectric and electromechanical properties of the glass ceramics are reported. Some of the compositions exhibit low temperature coefficient of resonance, comparable to LiTaO3 single crystals. Advantages of fabricating glass‐ceramic piezoelectric resonators are described and the possibility of using them in surface acoustic wave (SAW) devices is suggested.
15 citations
Journal Article•
13 citations
TL;DR: In this article, composites of SbSI and Spurrs epoxy in 1:3 and 3:3 modes were prepared, and the dielectric strain coefficients were measured over a temperature range encompassing the transition temperature.
Abstract: Following the principle of connectivity in two phase systems, composites of SbSI and Spurrs epoxy in 1:3 and 3:3 modes were prepared. Piezoelectric strain coefficients d 33 and d h, and dielectric constant K were measured over a temperature range encompassing the transition temperature. Interactions between the polymer and SbSI cause a shift in the dielectric peak to higher temperatures. The hydrostatic voltage coefficient g h, ≃ 110 × 10−3 m 2/C and hydrophone sensitivity d h·gh ≃ 10−10 m 2/N are substantially higher than those of SbSI single crystals and most other piezoelectrics.
11 citations
TL;DR: Cubic perovskites A(B 1 4 Nb 3 4 ) O 3 (A = Ba or Sr, B = Na or Li ) were prepared by solid state reaction at 1000°C for 3 hours, starting with oxides or carbonates of the various elements as discussed by the authors.
9 citations
TL;DR: In this paper, a simple model based on the polarization critical-fluctuation was proposed for temperature dependence of the electrostrictive coefficients of K(Ta 0.55 Nb 0.45 )O 3 in a narrow temperature range above the ferroelectric Cuire point (T - T C <30°C).
Abstract: A significant temperature dependence of the electrostrictive coefficients of K(Ta 0.55 Nb 0.45 )O 3 has been observed in a narrow temperature range above the ferroelectric Cuire point ( T - T C <30°C). The reciprocal permittivity versus temperature relation deviates from the Curie-Weiss law in the same temperature range. A simple model is proposed based on the polarization critical-fluctuation.
9 citations
TL;DR: In this article, the spontaneous strain and optical birefringence Anab in single ferroelectric PbBi2Nb2O9 are shown to be a function of the state of electrical poling.
Abstract: X-ray and optical measurements are used to show that the spontaneous strain (b/a-1) and optical birefringence Anab in single crystals of ferroelectric PbBi2Nb2O9 are a function of the state of electrical poling, going to a zero in the unpoled state. In poled crystals all spontaneous strain is lost at a temperature ∼220°C below the dielectric Curie temperature in a manner reminiscent of the behavior of the perovskite relaxer ferroelectrics which have diffuse phase transitions
6 citations
TL;DR: In this article, pyroelectric depolarization measurements taken using a Hewlett Packard Model 4140B picoammeter/DC Source under computer controlled heating cycle also have shown different behaviors between disordered and ordered materials.
Abstract: It has been shown that quenched Pb(Scl/2Ta1/2)03 (PST) disordered ceramics and crystals show diffuse dispersive dielectric properties, while well annealed ordered materials exhibit normal sharp first order transition. The pyroelectric depolarization measurements taken using a Hewlett Packard Model 4140B picoammeter/DC Source under computer controlled heating cycle also have shown different behaviors between disordered and ordered materials In this work pyroelectric measurements by Chynoweth method under DC bias up to 1.8 KV/mm within a temperature range of 70°C around the temperature of maximum dielectric constant have been studied. A very significant enhancement of the pyroelectric signal under DC bias is observed in thermally quenched disordered samples. The largest enhancement of the signal appears at temperatures some degrees below the temperature of maximum dielectric constant The existence of microdomains in disordered materials is believed to be responsible for this new extrinsic component...
5 citations