Search

Abstract: K0.5(Nd1−xBix)0.5MoO4 (0.2 ≤ x ≤ 0.7) ceramics were prepared via the solid‐state reaction method. All ceramics densified below 720°C with a uniform microstructure. As x increased from 0.2 to 0.7, relative permittivity (ɛr) increased from 13.6 to 26.2 commensurate with an increase in temperature coefficient of resonant frequency (TCF) from – 31 ppm/°C to + 60 ppm/°C and a decrease in Qf value (Q = quality factor; f = resonant frequency) from 23 400 to 8620 GHz. Optimum TCF was obtained for x = 0.3 (−15 ppm/°C) and 0.4 (+4 ppm/°C) sintered at 660 and 620°C with ɛr ~15.4, Qf ~19 650 GHz, and ɛr ~17.3, Qf ~13 050 GHz, respectively. Ceramics in this novel solid solution are a candidate for ultra low temperature co‐fired ceramic (ULTCC) technology. [ABSTRACT FROM AUTHOR]

In the present work, ( Bi1− x Fe x) VO4 ( x ≤ 0.40) ceramics were prepared using the solid-state reaction method. All the ceramics could be well densified at sintering temperatures below 800°C. X-ray diffraction ( XRD) results showed that monoclinic solid solution was formed within x ≤ 0.08. When x ≥ 0.10, both monoclinic scheelite and FeVO4 phases were detected. The ( Bi0.92 Fe0.08) VO4 sample sintered at 720°C for 2 h had a permittivity of 57.5 and a Qf value of 15 000 GHz. The IR reflectivity was fitted to study the intrinsic dielectric properties, showing that the majority of the dielectric contribution for this system at microwave region was attributed to the absorptions of structural phonon oscillation in infrared region. [ABSTRACT FROM AUTHOR]

(Bi 1−x Ln x ) 2 MoO 6 (Ln=Nd and La) ceramics were prepared by conventional solid state reaction method. Solid solutions crystallizing in a monoclinic structure with a space group P 21/ c were obtained in the (Bi 1−x La x ) 2 MoO 6 (x≤0.3) ceramics. For the (Bi 1−x Nd x ) 2 MoO 6 ceramics, tetragonal Nd 2 MoO 6 phase with a space group I4 1 /acd was detected when x value reached 0.2 besides the Bi 2 MoO 6 solid solution. Temperature stability and quality factor Qf value at microwave frequencies were improved by appropriate substitution for Bi 3+ by Nd 3+ and/or La 3+ in Bi 2 MoO 6 system. When x=0.2, for both (Bi 1−x Nd x ) 2 MoO 6 and (Bi 1−x La x ) 2 MoO 6 ceramics, Qf values reached maximum about 30,200 GHz and 32,900 GHz, respectively. TCF value shifted towards zero with substitution of Bi 3+ by Nd 3+ and/or La 3+ . When x=0.3, TCF values of (Bi 1−x Nd x ) 2 MoO 6 and (Bi 1−x La x ) 2 MoO 6 ceramics were −70 and −85 ppm/°C, respectively. Relation between crystal structure, microstructure and microwave dielectric properties were discussed. [ABSTRACT FROM AUTHOR]

Phase structure and dielectric behavior of Bi 3 (Nb 0.9 M 0.1 )O 7+δ ceramics (M = Ti, Zr, Sn, W, δ = ±0.05) were discussed. Cubic fluorite solid solutions Bi 3 (Nb 0.9 M 0.1 )O 7+δ (M = Zr, Sn, W, δ = ±0.05) were obtained through a conventional solid state reaction method. An analysis of the microwave dielectric properties showed that substitution of Nb 5+ by W 6+ was favorable to improving the temperature coefficient of resonant frequency (TCF value). A temperature stable dielectric material Bi 3 (Nb 0.9 W 0.1 )O 7.05 was introduced. The Bi 3 (Nb 0.9 W 0.1 )O 7.05 ceramics sintered at 930 °C for 2 h exhibited a high permittivity of 92.4, a Qf value of 260 GHz and a TCF value of −34 ppm/°C. [ABSTRACT FROM AUTHOR]