Microwave dielectric properties of bismuth-substituted Ba3.75Nd9.5Ti17Al4/3O54 ceramics

Abstract

The impact of bismuth substitution at neodymium (Nd) site in aluminum-replaced Ba 3.75 Nd 9.5 Ti 18 O 54 ceramics on dielectric constant (e r ), quality factor (Qf), and temperature coefficient of resonant frequency (s f ) has been determined (0.05 B x B 0.2). With appropriate quality factor values (Qf [ 5000 GHz), the dielectric constant increased from 74.42 to a maximum of 90.8 and the temperature coefficient of resonant frequency was tailored from approximately ?20 ppm/°C to the vicinity of 0 ppm/°C . The X-ray diffraction patterns showed a single phase for all compositions, while the scanning electron microscopy and energy-dispersive spectrometer data confirmed XRD results. Factors, such as bulk density, average polarizability, microstructure, and tolerance factor which were caused by the substitution, were taken into consideration to discuss the microwave dielectric properties' variation. Within substituting limit, a series of controllable microwave dielectric properties (e r = 75.8, Qf = 8994 GHz, s f = 7.2 ppm/°C; e r = 79.1, Qf = 7282 GHz, s f = 2.3 ppm/°C; e r = 87.07, Qf = 5548 GHz, s f = -8.6 ppm/°C) could be obtained when sintered at 1350°C for 2 h for x = 0.05, 0.1, and 0.15, respectively.

Microwave dielectric properties of (1‐x)Ba3.75Nd9.5Cr0.25Nb0.25Ti17.5O54–xNdAlO3 ceramics

“…Thus, it is reasonable to set x as zero and the total quality factor is dominated by the BaNd 2 Ti 4 O 12 phase. Prior reports on Ba 6‐3x Nd 8+2x Ti 18 O 54 ceramics show that their quality factors are mostly in the vicinity of 3000 ( f ~4 GHz) . Thus, quality factors of around 3000, far less than the quality factor of the NdAlO 3 phase, is reasonable .…”

“…Microstructures of samples sintered at 1425°C are shown in Figure . All compositions show rod‐like grains, which are typically observed in Ba 6‐3x Nd 8+2x Ti 18 O 54 ceramics . The surface of the sample without NdAlO 3 dopant is comprised of large‐ and small‐ size grains.…”

“…All compositions show rod-like grains, which are typically observed in Ba 6-3x Nd 8+2x Ti 18 O 54 ceramics. 2,7,[24][25][26] The surface of the sample without NdAlO 3 dopant is comprised of large-and small-size grains. As x increases from 0 to 0.6, more and more grains grow longer and more robust.…”

Microstructure and microwave dielectric properties of BaNd2Ti4−xAl4x/3O12 ceramics

“…Matjaz Valant et al [7] demonstrated that the s f value was closely related to the ratio of mean radii (r A /r B ) of A and B-site ions. Among current commercial microwave dielectric materials, extensive attention has been focused on A-site substitution for Ba 6-3x Nd 8?2x Ti 18 O 54 ceramics to lower the s f while the dielectric loss climbed steeply [8][9][10][11][12][13]. Al 3?…”

PHASE EVOLUTION AND MICROWAVE DIELECTRIC PROPERTIES OF Ca0.61Nd0.26Ti1-x (Al1/2Nb1/2)xO₃ CERAMICS (0 ≤ x ≤ 0.2)

“…The high dielectric constant ceramics of CaTiO 3 [4], BaO-Nd 2 O 3 -TiO 2 [5], and Bi 2 O 3 -V 2 O 5 [6] are intensively reported and CaTiO 3 shows the highest relative permittivity. Until now, many reports on the ionic substitution in CaTiO 3 have been proved as an effective way modifying the temperature coefficient at the resonant frequency to zero.…”