The microwave dielectric properties and the microstructures of Nd(Zn1/2Ti1/2)O3 (NZT) ceramics prepared by the conventional solid‐state route have been studied. The prepared NZT exhibited a mixture of Zn and Ti showing 1:1 order in the B‐site. The dielectric constant values (ɛr) saturated at 29.1–31.6. The quality factor (Q×f) values of 56 700–170 000 (at 8.5 GHz) can be obtained when the sintering temperatures are in the range of 1300°–1420°C. The temperature coefficient of resonant frequency τf was not sensitive to the sintering temperature. The ɛr value of 31.6, the Q×f value of 170 000 (at 8.5 GHz), and the τf value of −42 ppm/°C were obtained for NZT ceramics sintering at 1330°C for 4 h. For applications of high selective microwave ceramic resonators, filters, and antennas, NZT is proposed as a suitable material candidate.

The microwave dielectric properties and microstructures of an Mg(Zr 0.05 Ti 0.95 )O 3 ceramic system have been investigated. The compounds were prepared by the conventional solid-state route, and sintered at 13601-14501C for 2-6 h. The structure and microstructure were analyzed using X-ray diffraction and scanning electron microscopy techniques. The Mg(Zr 0.05 Ti 0.95 )O 3 had excellent dielectric properties: Q Â f 5 380 000 (GHz), e r 5 18.1, and s f 5 À50 ppm/1C for the sample at 14201C/4 h. These properties were correlated with the formation of second phases, Mg 2 TiO 4 and Mg 0.25 Zr 0.38 Ti 0.38 O 1.75 .

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A new ultra low loss microwave dielectric ceramic, Mg(Sn0.05Ti0.95)O3 (MSnT), was found and investigated. The compounds were prepared by the conventional solid‐state route, and sintered at 1360°–1480°C for 2–6 h. The investigations show that the MgTi2O5 secondary phase was observed. Moreover, the dielectric properties were correlated with the formation second phase. The excellent microwave dielectric properties of Q×f=322 000 (GHz), ɛr=17.4, and τf=−54 ppm/°C were obtained from the new MSnT ceramics sintered at 1390°C for 4 h.

High-dielectric-constant and low-loss ceramics in the (1Àx)Nd(Zn 1/2 Ti 1/2 )O 3 -xSrTiO 3 system have been prepared by the conventional mixed-oxide route and their microwave dielectric properties have been investigated. A two-phase system was confirmed by the X-ray diffraction patterns, the energy-dispersive X-ray spectrometer analysis, and the measured lattice parameters. Addition of SrTiO 3 , having a much smaller grain size in comparison with that of Nd(Zn 1/2 Ti 1/2 )O 3 , could effectively hold back abnormal grain growth in the Nd(Zn 1/2 Ti 1/2 ) O 3 matrix. Evaporation of Zn at high temperatures caused an increase in the dielectric loss of the system. The temperature coefficient of resonant frequency increases with increasing SrTiO 3 content and tunes through zero at x 5 0.52. Specimens with x 5 0.52 possessed an excellent combination of microwave dielectric properties: e r B54.2, Q Â f B84 000 GHz, and s f B0 ppm/1C. It is proposed as a suitable candidate material for today's 3G passive components and small-sized GPS patch antennas.

The monopole dumbbell‐shaped antenna fed by a 50 Ω microstrip line for ultrawideband (UWB) application is studied. By tuning the dumbbell‐shaped radiator and height of the feed gap (D), the monopole antenna has a 2:1 VSWR (return loss < 10 dB) from 2.89 to more than 15 GHz. The bandwidth covered 3.1–10.6 GHz, which has approved by the Federal Communications Commission as a commercial UWB band. Moreover, the antenna features near omnidirectional characteristics in the operation range and good radiation efficiency. The UWB, monopole characteristics of the antenna are confirmed experimentally. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1470–1473, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22404

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