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

Abstract

r o s s M a t e r i a l s R e s e a r c h L a b o r a t o r y The P e n n s y l v a n i a S a t e U n i v e r s i t y U n i v e r s i t y P a r k , PA 16802 Ab s t r a c t S i n g l e c r y s t a l s of l e a d b a r i u m 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 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 a n d 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 m o r p h o t r o p i c p h a s e boundary e x i s t s a t a b o u t Pb0.6Ba0.4Nb206. C u r r e n t u n d e r s t a n d i n g b a s e d o n 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 a n d 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 Pbl-BaXNb2O6 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 c o m p o s i t i o n s 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 a n d 0 . 4 0 a n d o n e 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 c o n f i r m t h e p r e d i c t i o n s made by t h e p h e n o m e n o l o g i c a l thermodynamic t h e o r y . 1. I n t r o d u c t i o n Among t h e v a r i o u s f e r r o e l e c t r i c m a t e r i a l s , a number o f n i o b a t e s h a v i n g t e t r a g o n a l o r r e l a t e d o r t h o r h o m b i c t u n g s t e n -b r o n z e s t r u c t u r e h a v e a t t r a c t e d a g r e a t d e a l o f a t t e n t i o n d u e t o t h e [I]. The t u n g s t e n -b r o n z e m a t e r i a l s w i t h o v e r 150 i n d i v i d u a l e n d m e m b e r c o m p o s i t i o n s a n d w i t h o c t a h e d r a based f e r r o e l e c t r i c s [ 2 1 . One o f t h e t u n g s t e n -b r o n z e f e r r o e l e c t r i c s , PbNb206 w a s d i s c o v e r e d b y Goodman i n 1 9 5 3 131. A f t e r t h i s d i s c o v e r y , a g r e a Pb 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 t h e n s t a b i l i z e s a t e t r a g o n a l s t r u c t u r e w i t h c o m p o s i t i o n s up t o Pb0.2Ba0.8Nb206. A 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 e x i s t s n e a r t h e c o m p o s i t i o n Pb0.6Ba0.4Nb206 [41. P r o p e r t i e s of s i n g l e c r y s t a l s w i t h c o m p o s i t i o n s c l o s e t o t h e b o u n d a r y a r e o f m a j o r i m p o r t a n c e f r o m f u n d a m e n t...

The Growth and Properties of Relaxor‐Based Ferroelectric Single Crystals

“…In 1959 and 1961, PMN and PZN crystals were first grown from the flux of PbO, 3,5 and their relaxor behavior was first reported in 1961 4 . After this, many researchers have obtained PMN and PZN single crystal by the flux method mainly using PbO or B 2 O 3 9–13 . At the compositions near morphotropic phase boundary (MPB), PZNT single crystal exhibits ultrahigh piezoelectric response, where its piezoelectric constant d 33 and electromechanical coupling factors k 33 achieved 1500–1570 pC/N and 90%–92% separately 14,15 .…”

“…4 After this, many researchers have obtained PMN and PZN single crystal by the flux method mainly using PbO or B 2 O 3 . [9][10][11][12][13] At the compositions near morphotropic phase boundary (MPB), PZNT single crystal exhibits ultrahigh piezoelectric response, where its piezoelectric constant d 33 and electromechanical coupling factors k 33 achieved 1500-1570 pC/N and 90%-92% separately. 14,15 The orientation of rhombohedral PZNT crystal with optimized d 33 is along the /001S direction rather than its spontaneous polarization /111S direction.…”

Pulsed laser deposition of a PBN:65 morphotropic phase boundary thin film with large electrostriction

“…The ferroelectric lead barium niobate solid-solution system, Pb 1−x Ba x Nb 2 O 6 (PBN:1-x), is potentially important for optical and electronic applications because of its unique properties as a tungsten bronze-type ferroelectric relaxor with a MPB that separates the tetragonal ferroelectric phase from the orthorhombic ferroelectric phase [1][2][3][4][5]. For PBN compositions near the MPB, the electro-optic (EO) [6], piezoelectric [3], electrostrictive, and pyroelectric [7] properties are enhanced and are expected to be temperature invariant because the MPB composition does not vary significantly with temperature.…”