Ferroelectric properties of the tungsten bronze M2+6M4+2Nb8O30 solid solution systems

Characterization and dielectric properties of Ba5LnNiTa9O30 (Ln = La, Nd and Sm) ceramics

“…Since the distortion from tetragonal symmetry (4 mm) to orthorhombic symmetry (mm2) is very weak, it is difficult to determine the symmetry of tungsten-bronze compounds by the X-ray powder diffraction and often requires other techniques such as ferroelectric, dielectric or optical measurements [2,3,10]. In this study Ba 5 LnNiTa 9 O 30 is found to be tetragonal tungsten-bronze structure (TTB) by latter dielectric measurements.…”

“…Ferroelectric tungsten-bronze compounds usually can be divided into two groups: those with tetragonal symmetry (4 mm), which undergo only one phase transition corresponding to tetragonal ferroelectric (4 mm) to tetragonal paraelectric (4/mmm), and those with orthorhombic symmetry (mm2) which are both and ferroeleastic, and undergo two phase transitions corresponding to orthorhombic ferroeleastic (mm2) to tetragonal ferroelectric (4 mm) and from ferroelectric to paraelectric [2,3]. Since the distortion from tetragonal symmetry (4 mm) to orthorhombic symmetry (mm2) is very weak, it is difficult to determine the symmetry of tungsten-bronze compounds by the X-ray powder diffraction and often requires other techniques such as ferroelectric, dielectric or optical measurements [2,3,10].…”

“…Some paraelectric niobates and with high dielectric constant and low loss are also very important due to the rapid progress in microwave telecommunications, satellite broadcasting and L. Fang [7][8][9]. The TB structure consists of a complex array of distorted BO 6 octahedra sharing corners in such a way that three different types of interstices (A, B and C) are available for a wide variety of cations occupying in the general formula (A 1 ) 2 (A 2 ) 4 (C) 4 (B 1 ) 2 (B 2 ) 8 O 30 [1][2][3]. Generally, the smallest interstice C is empty, so the general formula is A 6 B 10 O 30 for the filled tungsten-bronze structure.…”

“…Recently, some ferroelectric niobates and tantaltes with tungsten-bronze (TB) structure have attracted much attention due to their interesting ferroelectric, pyroelectric, piezoelectric, and nonlinear optic properties for applications in various electric devices, such as transducers, actuators, capacitors, and ferroelectric random access memory [1][2][3][4][5][6]. Some paraelectric niobates and with high dielectric constant and low loss are also very important due to the rapid progress in microwave telecommunications, satellite broadcasting and L. Fang [7][8][9].…”

Enhancement of dielectric properties by optimization of sintering condition in tungsten–bronze structured Ba5SmTi3Nb7O30 ferroelectric ceramics

“…Materials in different structural groups like perovskite, tungsten-bronze (TB), spinel, pyrochlore are now well known [2][3][4][5][6][7]. Some niobates and tantalates with TB structure have attracted attention because of their interesting ferroelectric, pyroelectric, piezoelectric and nonlinear optical properties [8][9][10][11][12][13][14]. The TB-type structure consists of a complex array of distorted BO 6 octahedra sharing corners in such a way that three different types of interstices (A, B and C) are available for cation occupation in the general formula [(A 1 ) 4 (A 2 ) 2 (C) 4 ][(B 1 ) 2 (B 2 ) 8 ]O 30 [15].…”