Synthesis of Ba3ZnNb2O9−Sr3ZnNb2O9 solid solution and their dielectric properties

Abstract

Oxides of the type, Ba 3-x Sr x ZnNb 2 O 9 (0 ≤ ≤ x ≤ ≤ 3), were synthesized by the solid state route. Oxides calcined at 1000°C show single cubic phase for all the compositions. The cubic lattice parameter (a) decreases with increase in Sr concentration from 4⋅ ⋅0938(2) for x = 0 to 4⋅ ⋅0067(2) for x = 3. Scanning electron micrographs show maximum grain size for the x = 1 composition (~ 2 µ µm) at 1200°C. Disks sintered at 1200°C show dielectric constant variation between 28 and 40 (at 500 kHz) for different values of x with the maximum dielectric constant at x = 1.

Crystal Structures, Modeling, and Dielectric Property Relationships of 2:1 Ordered Ba3MM‘2O9(M = Mg, Ni, Zn; M‘ = Nb, Ta) Perovskites

“…If the tolerance factor is greater than unity, often no octahedral tilting is observed, whereas compositions with a tolerance factor less than unity typically undergo octahedral tilting distortions. , The series of Ba 3 MM‘ 2 O 9 (M = Mg, Ni, Zn; M‘ = Nb, Ta) perovskites that do not undergo an octahedral tilting distortion exhibit optimal dielectric properties. The perovskites Ba 3 MgTa 2 O 9 (BMT) and Ba 3 ZnTa 2 O 9 (BZT) possess high Q × f values and a near zero τ f . , The type of cation order influences the dielectric properties, with 2:1 order of the M and M‘ cations exhibiting a larger Q × f than 1:1 ordered and disordered perovskites. − Substitutions on the A-, M-, and M‘-site have been made extensively, but no alternative compounds have emerged for high- Q applications. − For example, B-site substitution of the identical ionic radius (0.78 Å) Nb 5+ for Ta 5+ results in crystallization of isostructural 2:1 ordered perovskites; however, the ε is higher, Q is lower, and τ f is more positive. The origins of the dielectric property differences between the isostructural compounds are not well-understood.…”

Perovskite-Type Metal Oxides Exhibiting Negligible Grain Boundary Resistance to Total Electrical Conductivity

“…Both the Sr and Ba compounds can be indexed on a simple cubic (∼4 A ˚) perovskite structure (Table 1 and Table S1 of the Supporting Information) in space group Pm3m, in which both the Zn and Nb are randomly distributed at the B-site, 24 which is consistent with the model of Anderson et al 25 However, the crystal structure of AZn 0.33 Nb 0.67 O 3 is known to exhibit several modifications, including disordered cubic and ordered hexagonal structures. [26][27][28][29][30][31][32][33] These allotropes are stabilized by different sintering temperatures. For example, Tolmer and Disgardin reported the formation of the hexagonal BaZn 0.33 Ta 0.67 O 3 at 1600 °C and a cubic phase at 1450 °C.…”

“…28 Thirumal and Ganguli prepared cubic Ba 3-x Sr x ZnNb 2 O 9 (0 < x < 0.3) by solid-state reaction at 1000-1200 °C. 29 Generally, a large difference in the ionic radius and charge of the B-site cations favors ordered perovskite structure over the random disordered cubic perovskite structure. Also, d o cations such as Nb 5þ and Ta 5þ exhibit secondorder Jahn-Teller distortions and are known to form out-of-center distorted octahedra in the perovskite-type structures.…”

Monoclinically distorted perovskites, A2ZnTiO6 (A=Pr, Gd): Rietveld refinement, and dielectric studies

“…We have been interested in oxides with tetra and pentavalent, B' and B" ions which have good dielectric properties [14][15][16]. In this paper the structure and dielectric properties of rare earth zinc titanates are described.…”