Infrared and terahertz dielectric spectra of novel Bi2O3–Nb2O5 microwave ceramics

Dielectric Dispersion at Microwave Frequencies of Some Low Loss Mixed Oxide Perovskites

“…According to the classical oscillator model, complex dielectric permittivity ε and ε can be expressed in the following equations [6][7][8][9][10][11][12][13][14][15][16]:…”

“…Many efforts have been made to understand the frequency dependent of complex permittivity, ε − jε [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Far infrared reflectivity spectra were usually obtained and transformed to the complex dielectric data by the Kramers-Kronig procedure and the classical oscillator model [6][7][8][9][10][11][12][13][14][15][16].…”

“…Far infrared reflectivity spectra were usually obtained and transformed to the complex dielectric data by the Kramers-Kronig procedure and the classical oscillator model [6][7][8][9][10][11][12][13][14][15][16]. However, loss tangent values of these perovskites are on the order of 10 −4 to 10 −5 , which can not be obtained by the traditional reflection/transmission spectra or impedance measurement techniques.…”

Low Temperature Cofired Ceramics

“…The d-form is stable in a narrow temperature range 729-825°C and the stability range can be brought down by suitable doping with Nb 2 O 5 , Ta 2 O 5 or with rare earth oxides [139][140][141][142][143][144][145]. The d-Bi 2 O 3 has 25% oxygen sites vacant and substitution of Nb 5þ for Bi 3þ leads to a reduction in oxygen vacancies [146][147][148][149][150]. The low-temperature a-Bi 2 O 3 transforms to face-centered cubic d-Bi 2 O 3 at 729°C [151,152].…”

“…Bismuthbased dielectric ceramics are known as low-fired materials and have been studied for use as low-temperature coefficient ceramic capacitors [160]. Valant et al [146,153,161] reported Bi 2 O 3 -Nb 2 O 5 as high-permittivity glass-free dielectrics for LTCC applications. Valant and Suvorov [161] found an unusual scattering of dielectric properties as a function of preparation temperature for x = 0.25 and was attributed to the formation of a tetragonal fluorite phase [154].…”