T.R. Gururaja

Sol-gel processing of 0.91Pb(Zn13Nb23)O3-0.09PbTiO3: Stabilization of the perovskite phase

Abstract 0.91Pb(Zn 1 3 Nb 2 3 )O 3 -0.09PbTiO 3 was prepared by a sol-gel route in which Zn and Nb were prereacted to form “Zn[Nb(OEt) 6 ] 2 ” in situ. Calcination conditions were varied to optimize the percentage of perovskite phase stabilized. The maximum amount of perovskite phase stabilized was 75%, which occurred at a calcination temperature of 1000°C.

Temperature Behavior of the Complex Piezoelectric-D31 Coefficient in Modified Lead Titanate Ceramics

Abstract Piezoelectric properties of modified lead titanate ceramics were investigated in an effort to explain the large electromechanical anisotropy observed in these materials. While the thickness coupling factor is approximately constant with temperature, the planar coupling factor becomes zero near room temperature, probably indicating a change in sign of the piezoelectric d 31 coefficient. It is shown that for an accurate description of the electromechanical behavior of modified lead titanate ceramics, all material constants relevant for the planar coupling mode ( s 11 , e 33 d 31 ) must be taken as complex. Possible contributions to the complex d 31 are discussed.

Electromechanical Properties of Calcium Modified Lead Titanate Ceramics

Some of the modified lead titanate ceramics exhibit large electromechanical anisotropy (i.e. large kfi ). However, their piezoelectric constant dj3 (=GOpC/N) is not Igrge. The primary cause of the low d, IS due to the relatively low dielectric constant K (=200) of ttese materials. In this paper, the calcium modified lead titanate ceramics were investigated to increase their d, , by increasing K with ion modifications while retaining their large kfi by optimizing the processing conditions. A large dG3 !=92pC/N? with large K (-456) and an infinite kfip were o tained in the composition Pb, Ca, Ti . 4(C01RW,R)0,0603 + 0.01 MnO sintered for 30 hrs an86poleGt g8kVlcm.

Piezoelectric properties of sol-gel-derived samarium-dysprosium-modified lead titanate ceramics

Samarium- and dysprosium-modified lead titanate ceramics have been prepared by a sol-gel route to utilize the finer control of the process on homogeneity and microstructure. By varying the sintering schedule (temperature and time) for samarium-modified PbTiO3, ceramics with grain sizes ranging from submicrometre to 4 μm have been prepared. The dielectric and piezoelectric properties of ceramics poled sequentially from 0 to 60 kV cm−1 are reported. The dependence of the electromechanical properties on grain size and poling conditions is discussed. It is shown that dysprosium behaves very differently to samarium, and the successful insertion of dysprosium into the Pb2+ sites to produce true dysprosium-modified PbTiO3 ceramics was not possible.

Relative dielectric permittivity of calcium aluminate cement-glass microsphere composites

Abstract Calcium aluminate cement (SECARTM 80) was loaded with 0, 27.5, 40, 50, 60 and 70 vol% hollow glass microspheres and processed macro-defect free by high shear mixing with polyvinyl alcohol as a rheological aid. Discs were formed by die-pressing and dielectric measurements obtained from 100 Hz to 2 MHz. Relative dielectric permittivity was lowered for all microsphere loadings and was lowest at 40 vol%, corresponding to an effective porosity of 21.7%. A direct correlation was found to exist between microsphere loading (effective porosity) and the relative dielectric permittivity. Volume loadings of 27.5 and 40% microspheres resulted in the largest number of unbroken microspheres after processing. When compared with four ideal dielectric mixing models, the cement-microsphere composites were found to correlate best with Maxwell and Lichtenecker mixing. Dissipation factor was lower over the measured frequency range for all microsphere loadings. No correlation was found to exist between effective porosity and dissipation factor. Dielectric losses at low frequencies can be attributed to unbound water and polyvinyl alcohol.

Preparation and Piezoelectric Properties of Fired 0-3 Composites

A new method of p reparing 0-3 composites with more than 70 volume percent filler particles is presented. C onventional and corona discharge poling techniques h ave been u sed to pole the composites. PZT-polymer composites p repared by this method (fired composites) exhibited five times larger ahgh figure of merit compared to those prepared by the conventional method. In fired PbTi03-polymer composites, almost saturation poling was achieved and the ahgh figure of merit was 1750~10-~~ m2N-l. A resonance technique was used to determine the piezoelectric coupling factors corresponding to different modes of v ibration. The technique is useful for analyzing the dynamic performance of single mode low mechanical Q transducers.

Macro-defect-free processing and low-frequency dielectric response of calcium aluminate cements

Abstract Eight commercial grade calcium aluminate cements were prepared macro-defect free by high shear mixing, lowering the water/cement ratio and using polyvinyl alcohol as a plasticizer. Samples for dielectric measurements were prepared by die pressing to form disks. Relative dielectric permittivity and dissipation factor were measured over the frequency range of 100 Hz to 1 MHz. Variations in frequency response and loss mechanism between the cements are related to bulk chemistry.

Possible Mechanisms for the Electromechanical Anisotropy in Modified Lead Titanate Ceramics

Note: Penn State Univ,Mat Res Lab,University Pk,Pa 16802H1145Times Cited:0Cited References Count:0 Reference LC-ARTICLE-1987-002 Record created on 2006-08-21, modified on 2017-05-10

0-3 Pieoelectric Ceramic-Polymer Composites Prepared by a New Method: Fired Composites

I n c o m p o s i t e s w i t h 0-3 c o n n e c t i v i t y , a l o a d i n g of m o r e t h a n 6 0 v o l u m e p e r c e n t p i e z o e l e c t r i c f i l l e r i s r e q u i r e d to a c h i e v e u s e f u l p i e z o e l e c t r i c p r o p e r t i e s . A l i m i t a t i o n o f t h e p r e s e n t l y u s e d f a b r i c a t i o n p r o c e d u r e is t h e d i f f i c u l t y i n p r e p a r i n g composi tes w i t h such h igh load ing . A new method of p repa r ing 0-3 composi tes is p r e s e n t e d i n t h i s p a p e r i n w h i c h more t h a n 7 0 Volk f i l l e r p a r t i c l e s can be i n c o r p o r a t e d e a s i l y . C o n v e n t i o n a l a n d c o r o n a d i s c h a r g e p o l i n g t e c h n i q u e s were used t o e l e c t r i c a l l y p o l a r i z e t h e c o m p o s i t e s . D i e l e c t r i c a n d p i e z o e l e c t r i c p r o p e r t i e s o f t h e s e c o m p o s i t e s a r e p r e s e n t e d i n t h i s p a p e r .