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Effect of reactant dispersion on formation of PZT solid solutions
150
DENSIFICATION
CERAMICS
OF a-AND P-Si3N4 UNDER PRESSURE
Tetsuo Yamada, Atsuhiko Mitsue Koizumi
Tanaka, Masahiko Shimada and
Effect of phase transformation, microstructural changes and bonding beetween grains of SisN4, without additives was studied by high pressuring hot-pressing using cy-and P-S&N4 as starting materials. Densification of SiJN4 did not depend on the difference of the phase in starting materials. During the hot pressing of &ijN4, a drastic change in grain morphology took place with the progress of phase transformation, and the final microstructure showed the existence of self bonding and the development of polyhedral grains. In the hot-pressing of P-Si3N4, no appreciable change in grain morphology was observed and densification was proceeded only due to a plastic deformation mechanism. Phase transformation seems to play a significant role in the bonding between grains.
FORMATION MECHANISM AND CERAMIC PROCESS OF THE FERROELECTRIC PEROVSKITES: Pb(Mg,,,Nbz,~)O, AND Pb(Fe1,2NbIj2)03
INTERNATIONAL,
Vol. 11, n. 4, 1985
ly widely used in electronic circuits, often determines the applications of these materials. In this article the current understanding of the mechanisms and their dependence on the composition of the ceramic and on the experimental parameters is reviewed. The electrical and mechanical losses are proportional to each other. The proportionality factor is determined by material parameters, such as dielectric constant, spontaneous polarization etc., and is independent of the specific loss mechanism. The losses below the Curie temperature are mainly caused by domain wall movements. Above the Curie temperature the losses drop rapidly to a residual level, caused by lattice - and microstructural effects. At higher temperatures the losses are governed by the electrical conductivity of materials. Of major importance for applications are the domain wall losses. Their dependence on doping, aging, field strenght, frequency and temperature is described and discussed. Models are presented that attribute the losses to the damping of a moving domain wall.
PRELIMINARY OBSERVATIONS ON THE MICROSTRUCTURE OF NUCLEAR WASTE GLASSES J.F. DeNatale, D.K. McElfresh,
and D.G. Howitt
M. Lejeune, J.P. Boilot The formation of the Pb (MgI13 Nb2,3)03 and Pb (Fe,,2 Nb1,2)03 phases with a perovskite type structure is directiy dependent on the reactivity of magnesium and ferric oxides to other phases belonging to the binary system PbO-Nb20s. Moreover, it is shown that the ceramic process influences the proportion of perovskite phases in comparison with parasite phases and also the densification of the samples. The optimization of the ceramic process allows to obtain a pure Pb(Fe,,2Nb,,2)OJ phase, but as far as Pb(Mg,,jNb2,J)Oj is concerned, a parasite phase is never entirely eliminated.
The microstructures of simulated nuclear waste glasses prepared by the mixing of glass frit and calcined waste oxides at lOOO’% are shown to contain well defined boundaries that are depleted of heavy elements. The development of small crystallites and phase separation have also been observed but no evidence of microcracking or interfacial separation at these discontinuities was found. The same glasses prepared at 1350% were quite uniform at the microstructural level.
HISTORY OF BIOCERAMICS S.F. Hulbert, L.L. Hench, D. Forbers, L.S. Bowman RECENT DEVELOPMENTS CHINA
OF CEMENT CHEMISTRY
IN The history of bioceramics is reviewed and the Current Status of the use of nearly inert, surface reactive, and resorbable bioceramics discussed.
Xue Jungan In recent years, much work has been done by the cement chemists in China centering on energy saving in cemet and concrete making and improving the properties of both.
PREPARATION (05x51.75)
OF GLASS-CERAMICS
Hiroshi Hasegawa, EFFECT OF REACTANT DISPERSION OF PZT SOLID SOLUTIONS
The reactions in the formation of PZT solid solutions were studied with particular reference to changing the dispersion of the reactants by altering the mixing conditions. The final homogenisation step was studied in detail. The effect on the electromechanical properties of the PXT ceramics were measured. The results of these studies are discussed.
SEM, TEM AND EPMA STUDY OF INTERGRANULAR PHASES IN ALUMINA CERAMICS L. Kulig, J. Toruri, H. Koztowska and
Short communication.
ELECTRICAL AND MECHANICAL FERROELECTRIC CERAMICS
Masahiko Shimada and Mitsue Koizumi
ON FORMATION
A. 1. Kingon, P. J. Terblanche and J. 6. Clark
H. Tomaszewski, M. WQcik
PbsGe3.,Si,011
LOSSES IN
H. H. Hsrdtl The magnitude of the electrical and mechanical losses of devices made from ferroelectric ceramics, which are current-
Glass-ceramics with a high transparency were prepared by the crystallization of 5Pb0*(3-X) Ge02*XSi02 glass. From the results of temperature dependence of the permittivity, the Curie temperatures of the products were estimated to be 175%, 115OC and 65% for the glass-ceramics 5Pb0*3Ge02, 5Pb0*2.5*Ge02*0.5Si02 and 5Pb0*2Ge024i02, respectively.
ACOUSTIC ACTIVITY IN A QUARTZ CONTAINING PORCELAIN SUBJECTED TO LOW RATE THERMAL CHANGES J. D. Fridez, C. Carry and A. Mocellin A typical quartz containing porcelain was subjected to various controlled temperature-time treatments in the 20-950% range and for up to several days. Special precautions were taken and acoustic emission internally generated by the material during these treatments were recorded. Both experimental observations and analysis for stress in the vicinity of quartz particles show that the following process accounts for a significant part of the overall material response: development of circumferential microcracks, even at room temperature, following some (possibly absent if the initial size of the crack initiating defect is sufficient) subcritical defect growth. Parameters affecting the detailed distribution
DENSIFICATION
CERAMICS
OF a-AND P-Si3N4 UNDER PRESSURE
Tetsuo Yamada, Atsuhiko Mitsue Koizumi
Tanaka, Masahiko Shimada and
Effect of phase transformation, microstructural changes and bonding beetween grains of SisN4, without additives was studied by high pressuring hot-pressing using cy-and P-S&N4 as starting materials. Densification of SiJN4 did not depend on the difference of the phase in starting materials. During the hot pressing of &ijN4, a drastic change in grain morphology took place with the progress of phase transformation, and the final microstructure showed the existence of self bonding and the development of polyhedral grains. In the hot-pressing of P-Si3N4, no appreciable change in grain morphology was observed and densification was proceeded only due to a plastic deformation mechanism. Phase transformation seems to play a significant role in the bonding between grains.
FORMATION MECHANISM AND CERAMIC PROCESS OF THE FERROELECTRIC PEROVSKITES: Pb(Mg,,,Nbz,~)O, AND Pb(Fe1,2NbIj2)03
INTERNATIONAL,
Vol. 11, n. 4, 1985
ly widely used in electronic circuits, often determines the applications of these materials. In this article the current understanding of the mechanisms and their dependence on the composition of the ceramic and on the experimental parameters is reviewed. The electrical and mechanical losses are proportional to each other. The proportionality factor is determined by material parameters, such as dielectric constant, spontaneous polarization etc., and is independent of the specific loss mechanism. The losses below the Curie temperature are mainly caused by domain wall movements. Above the Curie temperature the losses drop rapidly to a residual level, caused by lattice - and microstructural effects. At higher temperatures the losses are governed by the electrical conductivity of materials. Of major importance for applications are the domain wall losses. Their dependence on doping, aging, field strenght, frequency and temperature is described and discussed. Models are presented that attribute the losses to the damping of a moving domain wall.
PRELIMINARY OBSERVATIONS ON THE MICROSTRUCTURE OF NUCLEAR WASTE GLASSES J.F. DeNatale, D.K. McElfresh,
and D.G. Howitt
M. Lejeune, J.P. Boilot The formation of the Pb (MgI13 Nb2,3)03 and Pb (Fe,,2 Nb1,2)03 phases with a perovskite type structure is directiy dependent on the reactivity of magnesium and ferric oxides to other phases belonging to the binary system PbO-Nb20s. Moreover, it is shown that the ceramic process influences the proportion of perovskite phases in comparison with parasite phases and also the densification of the samples. The optimization of the ceramic process allows to obtain a pure Pb(Fe,,2Nb,,2)OJ phase, but as far as Pb(Mg,,jNb2,J)Oj is concerned, a parasite phase is never entirely eliminated.
The microstructures of simulated nuclear waste glasses prepared by the mixing of glass frit and calcined waste oxides at lOOO’% are shown to contain well defined boundaries that are depleted of heavy elements. The development of small crystallites and phase separation have also been observed but no evidence of microcracking or interfacial separation at these discontinuities was found. The same glasses prepared at 1350% were quite uniform at the microstructural level.
HISTORY OF BIOCERAMICS S.F. Hulbert, L.L. Hench, D. Forbers, L.S. Bowman RECENT DEVELOPMENTS CHINA
OF CEMENT CHEMISTRY
IN The history of bioceramics is reviewed and the Current Status of the use of nearly inert, surface reactive, and resorbable bioceramics discussed.
Xue Jungan In recent years, much work has been done by the cement chemists in China centering on energy saving in cemet and concrete making and improving the properties of both.
PREPARATION (05x51.75)
OF GLASS-CERAMICS
Hiroshi Hasegawa, EFFECT OF REACTANT DISPERSION OF PZT SOLID SOLUTIONS
The reactions in the formation of PZT solid solutions were studied with particular reference to changing the dispersion of the reactants by altering the mixing conditions. The final homogenisation step was studied in detail. The effect on the electromechanical properties of the PXT ceramics were measured. The results of these studies are discussed.
SEM, TEM AND EPMA STUDY OF INTERGRANULAR PHASES IN ALUMINA CERAMICS L. Kulig, J. Toruri, H. Koztowska and
Short communication.
ELECTRICAL AND MECHANICAL FERROELECTRIC CERAMICS
Masahiko Shimada and Mitsue Koizumi
ON FORMATION
A. 1. Kingon, P. J. Terblanche and J. 6. Clark
H. Tomaszewski, M. WQcik
PbsGe3.,Si,011
LOSSES IN
H. H. Hsrdtl The magnitude of the electrical and mechanical losses of devices made from ferroelectric ceramics, which are current-
Glass-ceramics with a high transparency were prepared by the crystallization of 5Pb0*(3-X) Ge02*XSi02 glass. From the results of temperature dependence of the permittivity, the Curie temperatures of the products were estimated to be 175%, 115OC and 65% for the glass-ceramics 5Pb0*3Ge02, 5Pb0*2.5*Ge02*0.5Si02 and 5Pb0*2Ge024i02, respectively.
ACOUSTIC ACTIVITY IN A QUARTZ CONTAINING PORCELAIN SUBJECTED TO LOW RATE THERMAL CHANGES J. D. Fridez, C. Carry and A. Mocellin A typical quartz containing porcelain was subjected to various controlled temperature-time treatments in the 20-950% range and for up to several days. Special precautions were taken and acoustic emission internally generated by the material during these treatments were recorded. Both experimental observations and analysis for stress in the vicinity of quartz particles show that the following process accounts for a significant part of the overall material response: development of circumferential microcracks, even at room temperature, following some (possibly absent if the initial size of the crack initiating defect is sufficient) subcritical defect growth. Parameters affecting the detailed distribution