Microwave dielectric properties of Mg4Nb2O9 ceramics produced by hydrothermal synthesis

Abstract

Mg 4 Nb 2 O 9 ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg 4 Nb 2 O 9 were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q×f o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. t f value of −17.1 ppm/°C was improved by the addition of TiO 2 and t f value of 6.7 ppm/°C was obtained at 20 wt% TiO 2 . Chemical compatibility of Mg 4 Nb 2 O 9 with Ag was tested to identity the possibility of using Mg 4 Nb 2 O 9 for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg 4 Nb 2 O 9 and Ag powder heat treated at 900°C, it was considered that the Mg 4 Nb 2 O 9 system is applicable to the multilayer microwave devices using Ag as an electrode.

Synthesis, characterization, and microwave dielectric properties of Mg4Nb2O9 ceramics produced through the aqueous sol–gel process

“…A minor phase of Mg 5 Nb 4 O 15 with orthorhombic symmetry was developed accompanying Mg 4 Nb 2 O 9 as separated phases just at 30.16 • and 31.30 • .As the temperature increasing to 850 • C, the intensity of the Mg 4 Nb 2 O 9 peaks was gradually enhanced and the Mg 5 Nb 4 O 15 phase had been found to nearly disappear. Using the sol-gel method, we found that the calcination temperature was remarkably decreased to 550 • C, in comparison to these of the conventional mixed oxide route reported earlier [2][3][4]7,8] and other chemical methods [9][10][11][12][13] as shown in Table 1.…”

“…And now there have been many investigations of the chemical processing methods [9][10][11][12][13], which have been developed as alternatives to the conventional solid state reaction of mixed oxides for producing ceramics to reduce the sintering temperature. For example, the MN ceramic was successfully fabricated at 950 • C for 2 h in air by the precipitation process with ε r = 8.5, Qf = 5500 GHz [9] and by a hydrothermal method the MN ceramic was obtained with the highest Qf value of 26,069 GHz at 1300 • C [12].…”

“…For example, the MN ceramic was successfully fabricated at 950 • C for 2 h in air by the precipitation process with ε r = 8.5, Qf = 5500 GHz [9] and by a hydrothermal method the MN ceramic was obtained with the highest Qf value of 26,069 GHz at 1300 • C [12]. Among the methods of wet chemical techniques, the sol-gel is undoubtedly one of a useful process for producing powders with a good control over stoichiometry and homogeneity, yielding nano-sized particles.…”

High quality factor of (Zn0.6Mg0.4)1.918GeO3.918 microwave dielectrics

“…Several dielectric ceramics with low K and high Qf value, such as Al 2 O 3 [2], Mg 4 Nb 2 O 9 [3], Ca 3 Sn 2 SiO 9 [4], Mg 2 SiO 4 [5], and Zn 2 SiO 4 [6] have received attention with respect to applications as ceramic substrate materials of microwave integrated circuits (MIC) to minimize the cross-coupling with conductors and to shorten the time for electronic signal transmission.…”

Microwave dielectric properties of Mg4Nb2O9 ceramics with excess Mg(OH)2 produced by a reaction-sintering process

“…coprecipitation, hydrothermal and sol-gel [1][2][3]. The Mg 4 Nb 2 O 9 (MN) ceramic by the conventional solid-state method possesses ε r =12.4, τ f =À 70 ppm/1C and a high Q Â f=193,000 GHz [4].…”