Showing papers by "L. E. Cross published in 1986"

Effect of elastic boundary conditions on morphotropic Pb(Zr,Ti)O 3 piezoelectrics

Abstract: Most of the technologically important transducers are made of poled-polycrystalline lead zirconate--lead titanate Pb(Zr,Ti)${\mathrm{O}}_{3}$ compositions near the morphotropic phase boundary where the [Zr]:[Ti] ratio is approximately 1:1. The effect of elastic boundary conditions on single-domain stability and properties of compositions near the morphotropic phase boundary in the ${\mathrm{PbZrO}}_{3}$-${\mathrm{PbTiO}}_{3}$ phase diagram is of considerable interest, since in a polycrystalline ensemble, the elastic and electric boundary conditions are uncertain. In this work, a phenomenological free-energy function which we developed earlier is used to determine the influence of elastic boundary conditions upon the relative stability points and the rhombohedral (R3m)--tetragonal (P4mm) degeneracy required for the morphotropy at [Zr]:[Ti] ratio near 1:1.

Electromechanical Properties of Calcium Modified Lead Titanate Ceramics

Abstract: 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.

Low‐temperature dielectric properties of SrTiO3 glass‐ceramics

Abstract: The low‐temperature dielectric properties of strontium titanate aluminosilicate glass‐ceramics, in which perovskite SrTiO3 is the primary crystalline phase, have been investigated. These glass‐ceramics exhibited dielectric constant peaks at temperatures below 100 K; the magnitude of these peaks, along with their frequency and temperature dependencies, were strongly dependent on the crystallization conditions. In heavily crystallized glass‐ceramics, two low‐temperature, relaxation‐type loss mechanisms were identified, at temperature ranges near 50 and 100 K. The magnitude of the dielectric loss peak increased with increasing frequency for the lower temperature (50 K) mechanism and the magnitude of the loss peak decreased with increasing frequency for the higher temperature (100 K) mechanism. Arrhenius activation energies were calculated to be 0.054 and 0.17 eV for the lower and higher temperature loss mechanisms, respectively. The higher temperature loss mechanism was further analyzed by the Cole–Cole meth...

Possible Mechanisms for the Electromechanical Anisotropy in Modified Lead Titanate Ceramics

Abstract: Lead titanate ceramics modified with samarium and calcium exhibit large anisotropy in electromechanical coupling factors. The planar coupling factor in these materials shows a strong temperature dependence passing through a minimum near room temperature whereas the thickness coupling factor remains practically a constant. To explain this behavior, the material coefficients characteristic for the planar coupling mode, such as d,,, sllEand E 3T, were investigated as a function of

Electromechanical Anisotropy in Modified Lead Titanate Ceramics

Abstract: Note: Penn State Univ,Mat Res Lab,University Pk,Pa 16802E6501Times Cited:0Cited References Count:0 Reference LC-ARTICLE-1986-001 Record created on 2006-08-21, modified on 2017-05-10

Electromechanical Anisotropy in Modified Lead Titanate Ceramics

Abstract: Note: Penn State Univ,Mat Res Lab,University Pk,Pa 16802E6501Times Cited:0Cited References Count:0 Reference LC-ARTICLE-1986-001 Record created on 2006-08-21, modified on 2017-05-10

First order transitions in perovskite ferroelectrics with oxygen octahedron tilts: Application to PZT

Abstract: A phenomenological theory for phase transitions in pervoskite ferroelectrics with oxygen octahedron tilts is worked out for first order transitions. After obtaining formal results for polarization, dielectric constant and tilt angle, the theory is applied to the lead zirconate-titanate system.

Growh and Dielectric Properties of Lead Barium Niobate Single Crystals and Morpeotropic Phase Boundary

Abstract: S i n g l e c r y s t a l s of l e a d bar ium n i o b a t e (PBN) b e l o n g i n g t o t h e t e t r a g o n a l t u n g s t e n b r o n z e s t r u c t u r e s p o s s e s s many d e s i r a b l e p r o p e r t i e s f o r p o t e n t i a 1 a p p l i c a t i o n s i n e 1 e c t r o o p t i c , p i e z o e l e c t r i c a n d p y r o e l e c t r i c d e v i c e s . I n t h e s o l i d s o l u t i o n PbNb206-BaNb206, s u b s t i t u t i o n o f b a r i u m f o r l e a d f i r s t d e c r e a s e s t h e o r t h o r h o m b i c d i s t o r t i o n and l a t e r s t a b i l i z e s t h e t e t r a g o n a l s t r u c t u r e . A morphot ropic phase boundary e x i s t s a t about Pb0.6Ba0.4Nb206. Cur ren t unde r s t and ing based on p h e n o m e n o l o g i c a l c a l c u l a t i o n s o n r e l a t e d m a t e r i a 1 s i n d i c a t e t h a t e 1 e c t r o o p t i c a n d d i e l e c t r i c p r o p e r t i e s o f PBN s h o u l d e x h i b i t c o n s i d e r a b l e e n h a n c e m e n t n e a r t h e m o r p h o t r o p i c p h a s e b o u n d a r y and t h a t t h e y s h o u l d b e l a r g e l y t e m p e r a t u r e i n d e p e n d e n t o v e r a r e a s o n a b l y l a r g e r a n g e o f t e m p e r a t u r e . A s a r e s u l t o f t h i s m o t i v a t i o n , we h a v e grown s i n g l e c r y s t a l s o f PblBaXNb2O6 e m p l o y i n g C z o c h r a l s k i t e c h n i q u e . R e s u f t s o f d i e l e c t r i c c o n s t a n t of two compos i t ions i n t h e o r t h o r h o m b i c s t r u c t u r e w i t h x = 0.37 and 0 . 4 0 a n d one c o m p o s i t i o n i n t h e t e t r a g o n a l s t r u c t u r e w i t h x = 0.65 a r e r e p o r t e d i n t h i s paper. These r e s u l t s l a r g e l y conf i rm t h e p r e d i c t i o n s made by t h e phenomenologica l thermodynamic theory .

Dielectric Aging Effects in Doped Lead Magnesium Niobate: Lead Titanate Relaxor Ferroelectric Ceramics

Abstract: contribute to aging in normal macro-domain ferroelectrics No obvious dielectric aging effects have been observed in pure .9Pb(Mgl13Nb2,3)03:. 1PbTi03 relaxor ferroelectric ceramics in this study. The addition of small amounts of MnO however, induces aging effects. Aging effects preferentially reduce the dispersive component of the weak field permittivities above the aging temperature. Isothermal aging rates are observed to increase with increasing doping level. Dielectric constants vs the logarithm of time at constant temperature level out with time. The origin of aging for this type of relaxor material can be explained in terms of the volume stabilization of the polar vectors in polar micro-regions by the defect dipoles introduced by the doping.

Dielectric Properties of RF Sputered Bismuth Titanate Thin Films

Abstract: S e v e r a l a t t e m p t s [S-101 have been made t o p r e p a r e s t o i c h i o m e t r i c Bi4Ti3OI2 f i l m s in o r d e r t o d u p l i c a t e i t s s i n g l e c r y s t a l p r o p e r t i e s . Var ious p r e p a r a t i o n t e c h n i q u e s , i n c l u d i n g RF s p u t t e r i n g . were used f o r t h e Bi4Ti3012 t h i n f i l m p repa ra t ion . In t h i s p a p e r we r e p o r t t h e p r e p a r a t i o n o f t h i n f i l m s of Bi4Ti3012 and t h e i r d i e l e c t r i c p r o p e r t i e s . Abs t roc t

Growth, Dielectric and Pyroelectric Properties of 0.9Pb(Zn l/3 Nb 2/3 )O 3 -0.1PbTiO 3 Single Crystals

Abstract: S i n g 1 e c r y s t a l s o r ' 0 .9 PD ( Z n l I 3 N b 2 030 . 1 P b T i 0 3 were g r o w n u s i n g t h e f l u x m e t h o d . T h e d i e l e c t r i c p r o p e r t y a l o n g t h e p s e u d o c u b i c [I111 and [ l o 0 1 d i r e c t i o n s was m e a s u r e d as a f u n c t i o n of t e m p e r a t u r e and f r e q u e n c y . T h e e f f e c t s o f p o l i n g a n d D C b i a s f i e l d were i n v e s t i g a t e d . T h e p y r o e l e c t r i c p r o p e r t y a l o n g t h e s e two d i r e c t i o n s was a l s o measured. 1. I n t r o d u c t i o n The Pb(Znl, 3Nb2, )03-PbTi03 (PZN-PT) s y s ten is known t o n a v e a n e a r m o r p h o t r o p i c p h a s e b o u n d a r y b e t w e e n t h e t e t r a g o n a l and r h o m b o h e d r a l p h a s e i n t h e range o f 9 t o 9.5 mole% P b T i 0 3 . C r y s t a l s w i t h more t h a n 9.5% P b T i 0 3 s h o w t e t r a g o n a l s y m m e t r y , w h i l e t h o s e w i t h l e s s t h a n 94, P b T i 0 3 s h o w rhombohedral symmetry t l l . C r y s t a l s w i t h 9% PbTi03 were f o u n d t o h a v e v e r y l a r g e 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 c o n s tan ts [ 2 I . I n t h i s p a p e r t h e g r o w t h and c h a r a c t e r i z a t i o n of c r y s t a l s w i t h s t a r t i n g c o m p o s i t i o n s 0.9PZN-O.1PT a r e d i s c u s s e d . T h e d i e l e c t r i c a n d p y r o e l e c t r i c p r o p e r t i e s a l o n g t h e p s e u d o c u b i c 1 1 1 1 1 a n d I 1 0 0 1 d i r e c t i o n s a n d t h e e f f e c t s of p o l i n g a n d DC b i a s f i e l d o n t h e d i e l e c t r i c b e h a v i o r a r e a l s o i n v e s t i g a t e d , 2 . C r y s t a l Growth S i n g 1 e c r y s t a l s 0 f 0. 9 P b ( Z n l 3 N b 2 1 030 . 1 P b T i 0 3 (PZNO.1PT) were g r o w n f r o m m o l t e n PbO f l u x by s l o w c o o l i n g . S t a r t i n g m a t e r i a l s were PbO. ZnO. N b 2 0 5 a n d T i 0 2 i n s t o i c h i o m e t r i c p r o p o r t i o n . A compound t o f l u x r a t i o o f 1 : 2 i n m o l e w a s u s e d . T h e c h a r g e was p l a c e d i n a p l a t i n u m c r u c i b l e a n d h e a t e d t o 1230°C. After a s o a k i n g p e r i o d o f 5 h r s , t h e c h a r g e was s l o w l y c o o l e d a t a r a t e of 3-SuC/hr t o 900°C a n d t h e n t o room t e m p e r a t u r e i n 2 4 h r s . T h e PbO t ' l u x w a s r e m o v e d by d i s s o l v i n g i n h o t a c e t i c a c i d . T h e c r y s t a l s o b t a i n e d a r e m o s t l y i n t h e form o f a n a r rowhead or i r r e g u l a r i n s h a p e w i t h a l i n e a r d i m e n s i o n of 1 t o 3 mm. and h a v e brown c o l o r . Some s m a l l e r c r y s t a l s a l s o s h o w r e c t a n g u l a r f a c e s a n d h a v e l i g h t e r c o l o r . Back r e f l e c t i o n Laue t e c h n i q u e r e v e a l s t h a t t h e p s e u d o c u b i c 1 1 1 1 1 d i r e c t i o n i s a l o n g t h e d i r e c t i o n o f t h e a r rowhead and t h e I1001 d i r e c t i o n is normal t o t h e r e c t a n g u l a r race. X-ray p o w d e r d i f f r a c t i o n p a t t e r n s do n o t i n d e x a s a s i n g 1 e p h a s e . I m p o s i n g a PhOmbOhedPal s y m m e t r y r e s u l t s i n t h e p a r a m e t e r s a = 4.0501 and a = 80"54' x h i c h a c c o u n t for cer tain l i n e s , w h e r e a s i m p o s i n g a t e t r a o n a l s y m m e t r y r e s u l t s i n a = 4 . 0 2 8 1 . c = 4 . 0 8 4 f w h i c h a c c o u n t f o r t h e res t o f t h e l i n e s . T h e s e v a l u e s a g r e e v e r y w e l l w i t h t h e v a l u e s f o r t h e two p h a s e s as shown i n F ig . 1 i n R e f e r e n c e L11, i n d i c a t i n g t h a t b o t h t h e r h o m b o h e d r a l a n d tetragonal p h a s e s c o e x i s t . I n t h e a b o v e a n a l y s i s , a c o m p u t e r program u s i n g A p p l e m a n ' s l e a s t s q u a r e s method f o r c e l l r e f i n e m e n t 131 was used . C o m p o s i t i o n a n a l y s e s b y e l e c t r o n m i c r o p r o b e were p e r f o r m e d on arrowhead-shaped and r e c t a n g u l a r s a m p l e s f r o m two g r o w t h t r i a l s . T h e c o m p o s i t i o n f o r e a c h s a m p l e was o b t a i n e d from a v e r a g i n g t h e v a l u e s a t f i v e l o c a t i o n s , t h e two ar rowhead-shaped s a m p l e s h a v e 0 .113 a n d 0.117 p a r t s o f T i i n t h e o x i d e f o r m w h i l e t h e two r e c t a n g u l a r o n e s h a v e 0.117 a n d 0.129 p a r t s . The o v e r a l l a v e r a g e o f T i i s f o u n d t o b e .119 p a r t s whereas Zn i s l e a s t h a n t h e p r o p o r t i o n i n t h e s t a r t i n g f o r m u l a PbZn 3Nb 6Ti.103. L o s s o f Z n O t h r o u g h e v a p o r a t i o n took ' p l i c e d u r i n g g r o w t h d u e t o t h e h i g h e r i n i t i a l t e m p e r a t u r e . 3 . D i e l e c t r i c P r o p e r t i e s S a m p l e s i n p l a t e l e t form w i t h t h e major f a c e n o r m a l t o t h e p s e u d o c u b i c [lll] o r I1001 d i r e c t i o n were p r e p a r e d . B a c k r e f l e c t i o n Laue , m e t h o d w a s u s e d i n o r i e n t i n g s a m p l e s . The d i e l e c t r i c c o n s t a n t K a n d l o s s a l o n g t h e p s e u d o c u b i c 11111 a n d [ l o 0 1 d i r e c t i o n s were m e a s u r e d a s a f u n c t i o n o f t e m p e r a t u r e a t f o u r f r e q u e n c i e s : 0 .1 , 1, 1 0 a n d 100 KHz a n d f o r u n p o l e d a n d p o l e d s t a t e s . P o l i n g w a s e f f e c t e d by c o o l i n g t h e s a m p l e f r o m 200°C t o 0°C u n d e r a D C f i e l d o f 1 0 K V l c m . F i g s . 1 a n d 2 show t h e d i e l e c t r i c c o n s t a n t and loss as a f u n c t i o n of t e m p e r a t u r e f o r u n p o l e d s a m p l e s i n t h e [1111 and [ l a 0 1 d i r e c t i o n s , r e s p e c t i v e l y . T h e y s h o w t h e b e h a v i o r o f a r e l a x o r t y p e f e r r o e l e c t r i c . N e a r room t e m p e r a t u r e t h e r e i s a d i f f u s e d t r a n s i t i o n f r o m t h e rhombohedra l to t e t r a g o n a l p h a s e , and a t 1 7 5 ° C a t r a n s i t i o n from t h e t e t r a g o n a l t o c u b i c p h a s e w i t h i n c r e a s i n g t e m p e r a t u r e . F i g s . 3 a n d 4 show t h e e f f e c t o f p o l i n g . P o l i n g a l o n g t h e [1111 a n d L1001 d i r e c t i o n s h a s a v e r y d i f f e r e n t e f f e c t o n t h e K v s T c u r v e s . When p o l e d a l o n g 1 1 1 1 1 , K r i s e s s h a r p l y a t t h e r h o m b o h e d r a l t o t e t r a g o n a l (R-T) p h a s e t r a n s i t i o n , r e a c h i n g a v a l u e o f 1 2 , 0 0 0 s l i g h t l y a b o v e t h e 50000, , 0 . 2 0 CT 0 i L 0.15 5

Multilayer Actuator Design

Abstract: A finite difference method of analyzing actuators for electrostrictive and piezoelectric materials will be discussed. Recent analysis of devices via numerical techniques and applications to electromechanical systems are demonstrated. Operating parameters and ceramic systems for multiphase devices are proposed which show performance criteria for actuator applications. Examples of the numerical treatment of specific devices such as axial positioners and linear resonators will be included.