Structure and microwave dielectric properties of SrSmAlO4-Sr2TiO4 solid solutions

Abstract

The structure and microwave dielectric properties of Sr 1+x Sm 1-x Al 1-x Ti x O 4 ceramics were determined in the entire composition range of x=0~1.0. The single phase solid solutions with K 2 NiF 4 structure were obtained, and the Q×f value decreased with increasing x at first (up to 0.15) and then turned to increase and reached the maximum at x=0.9. The dielectric constant ε r increased from 19.2 to 36.5 and the temperature coefficient of resonant frequency τ f ascended monotonously with increasing x. The variation tendency of Q×f value with x reflected the competition result of the interlayer polarization and the structure inhomogeneity. On the other hand, infrared (IR) reflectivity spectra were measured and fitted by means of classical oscillator model simulation. The intrinsic dielectric loss tangent extrapolated from IR range showed a similar changing trend with the measured ones. Moreover, the fitting results offered a detail inside view of the intrinsic factors and the variation of the dielectric loss could be well explained.

(Sr1‐xCax)2TiO4 microwave dielectric ceramics with R‐P structure (x = 0~0.15)

“…24,25 Density, inhomogeneity, secondary phase, and grain boundary are attributed to the fundamental extrinsic factors deteriorating Qf value. 26,27 However, in terms of extrinsic dielectric loss a similar trend was observed by MM Mao 28 which implies that there is an obvious relation between intrinsic dielectric loss and actual crystal structure variation. 26,27 However, in terms of extrinsic dielectric loss a similar trend was observed by MM Mao 28 which implies that there is an obvious relation between intrinsic dielectric loss and actual crystal structure variation.…”

“…Since for the present ceramics, intrinsically because of different ionic radii of Sr 2+ (1.18Å) and Ca 2+ (1.00Å) 22 the interlayer mis-match and interlayer polarization increases which ultimately affects the Qf value. 26,27 However, in terms of extrinsic dielectric loss a similar trend was observed by MM Mao 28 which implies that there is an obvious relation between intrinsic dielectric loss and actual crystal structure variation. Therefore, the decrease in tolerance factor t as a function of x tends to reduce the structure stability through which there is an ultimate increase in internal stress, diminishing the Qf value in result.…”

Ruddlesden-Popper phase A2BO4 oxides: Recent studies on structure, electrical, dielectric, and optical properties

“…These distortions originate due to a large difference in the ionic radii of M and Ln cations, also leading to an interlayer size mismatch. Between these interlayers static electric polarization may also be present due to "2+" oxidation state of cation M and "3+" oxidation state of cation Ln (discussed in detail in Section 2) [21,134,136,137]. There are several studies in which improvement in × ( = = and = frequency) has been achieved by reducing interlayer static electric polarization [21,136,138,139].…”

Srn+1TinO3n+1 (n=1, 2) microwave dielectric ceramics with medium dielectric constant and ultra‐low dielectric loss

“…However, their reported high dielectric losses ( Q =2616 at 3.14 GHz for Sr 2 TiO 4 and Q =7450 at 2.53 GHz for Sr 3 Ti 2 O 7 ) are barely satisfactory and difficult to be understood due to the obvious impurity phase observed in the XRD patterns . It is well recognized that the microwave dielectric loss is divided into the extrinsic part and the intrinsic part . Moreover, the extrinsic dielectric loss, which originates from the crystal imperfection, plays the dominant role in determining the overall dielectric loss of microwave ceramics .…”

“…13 It is well recognized that the microwave dielectric loss is divided into the extrinsic part and the intrinsic part. 14,15 Moreover, the extrinsic dielectric loss, which originates from the crystal a Fellow, The American Ceramic Society. imperfection, plays the dominant role in determining the overall dielectric loss of microwave ceramics.…”