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Abstract: The microwave dielectric properties of (Mg(1−x)Zn x )2SnO4 ceramics were examined with a view to their exploitation for mobile communication. The (Mg(1−x)Zn x )2SnO4 ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the (Mg0.93Zn0.07)2SnO4 ceramics revealed no significant variation of phase with sintering temperatures. Dielectric constant of 8.50, quality factor (Q × f) of 186,100GHz, and temperature coefficient of resonant frequency of −61ppm/°C were obtained for (Mg0.93Zn0.07)2SnO4 ceramics that were sintered at 1550°C for 4h. [Copyright &y& Elsevier]

Abstract: The microwave dielectric properties of La(Mg0.5−x Ni x Sn0.5)O3 ceramics were examined with a view to their exploitation for mobile communication. The La(Mg0.5−x Ni x Sn0.5)O3 ceramics were prepared by the conventional solid-state method at various sintering temperatures. The X-ray diffraction patterns of the La(Mg0.4Ni0.1Sn0.5)O3 ceramics revealed no significant variation of phase with sintering temperatures. Apparent density of 6.71g/cm3, dielectric constant (ɛ r ) of 20.19, quality factor (Q × f) of 74,600GHz, and temperature coefficient of resonant frequency (τ f ) of −85ppm/°C were obtained for La(Mg0.4Ni0.1Sn0.5)O3 ceramics that were sintered at 1550°C for 4h. [Copyright &y& Elsevier]

Abstract: The microwave dielectric properties of La(1−2x/3)Sr x (Mg0.5Sn0.5)O3 ceramics were examined with a view to their exploitation for mobile communication. The La(1−2x/3)Sr x (Mg0.5Sn0.5)O3 ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction peaks of the La(1−2x/3)Sr x (Mg0.5Sn0.5)O3 ceramics shifted to lower angles as x increased from 0 to 0.05. The X-ray diffraction patterns of the La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics revealed no significant variation of phase with sintering temperatures. A maximum density of 6.56g/cm3 was obtained for La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramic, sintered at 1550°C for 4h. A dielectric constant (ɛ r ) of 20.0 and a product of quality factor and resonant frequency (Q × f) of 57,100GHz and a temperature coefficient of resonant frequency (τ f ) of −77ppm/°C were obtained for La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics that were sintered at 1550°C for 4h. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the dielectric properties of Ca1−x Mg x La4Ti5O17 ceramics at microwave frequency have been studied. The diffraction peaks of Ca(1−x)Mg x La4Ti5O17 ceramics nearly unchanged with x increasing from 0 to 0.03. Similar X-ray diffraction peaks of Ca0.99Mg0.01La4Ti5O17 ceramic were observed at different sintering temperatures. A maximum density of 5.3g/cm3 can be obtained for Ca0.99Mg0.01La4Ti5O17 ceramic sintered at 1500°C for 4h. A maximum dielectric constant (ɛ r ) and quality factor (Q × f) of Ca0.99Mg0.01La4Ti5O17 ceramic sintered at 1500°C for 4h are 56.3 and 12,300GHz (at 6.4GHz), respectively. A near-zero temperature coefficient of resonant frequency (τ f ) of −9.6ppm/°C can be obtained for Ca0.99Mg0.01La4Ti5O17 ceramic sintered at 1500°C for 4h. The measurement results for the aperture-coupled coplanar patch antenna at 2.5GHz are presented. With this technique, a 3.33% bandwidth (return loss <−10dB) with a center frequency at approximately 2.5GHz has been successfully achieved. [Copyright &y& Elsevier]

Abstract: Photoluminescence investigation of Eu and Dy activated phosphate based phosphors prepared by combustion synthesis, characterized by XRD (X-ray diffraction) and photoluminescence techniques, has been reported. PL excitation spectrum of M5(PO4)3F:Dy phosphors shows the excitation peaks ranging from 300 to 400nm due to 4f→4f transitions of Dy3+ ions. PL emission spectrum of Dy3+ ion under 348nm excitation gives PL emission at 482nm (blue) due to 4F9/2 → 6H15/2 transitions, 574nm (yellow) emission due to 4F9/2 → 6H13/2 transitions and 670nm (red) due to 4F9/2 → 6H11/2 transitions, gives BYR (blue–yellow–red) emissions. The Eu2+ broad band PL emission spectrum was observed in M5(PO4)3F:Eu phosphor at 440nm in the blue region of the spectrum due to 5d→4f transition at 352nm excitation. The 300–400nm is Hg-free excitation (Hg excitation is 85% 254nm wavelength of light and 15% other wavelengths), which is characteristic of solid-state lighting phosphors. Hence PL emission in divalent europium and trivalent dysprosium may be efficient photoluminescent materials for solid-state lighting phosphors. [Copyright &y& Elsevier]