Phase Constitutions and Microwave Dielectric Properties of Zn₃Nb₂O₈–TiO₂

Abstract

The phase constitutions and microwave dielectric properties of (1-x)Zn3Nb2O8–xTiO2 were investigated using X-ray powder diffraction and a network analyzer, respectively. Four mixture regions were studied with increasing TiO2 content (x): (1) Zn3Nb2O8, ZnNb2O6, and Zn2TiO4, (0<x≤0.5) (2) ZnNb2O6 and Zn2TiO4, (0.5<x<0.65) (3) Zn2TiO4, ZnTiNb2O8, and TiO2 (0.65≤x≤0.75), (4) Zn2TiO4 and TiO2 (0.75<x<1). This structural evolution with composition was ascribed to the interrelations between Zn3Nb2O8 and TiO2. It was demonstrated that the microwave dielectric properties correlated to crystal structure rather than chemical composition. In the mixture region of Zn2TiO4, ZnTiNb2O8, and Zn2TiO4, the amount of TiO2 and ZnTiNb2O8 considerably increased and decreased, respectively, with increasing TiO2 content (x). This resulted in the increase of relative dielectric constant (ε r) and temperature coefficient of resonant frequency (τf). At x=0.725, Q×f is 5190 GHz, ε r and τf are 36 and 4 ppm/°C, respectively.

New high-ɛ and high-Q microwave dielectric ceramics: (1−x)Ca0.61Nd0.26TiO3−xNd(Zn0.5Ti0.5)O3

“…And the (1 − x)CNT − xNZT ceramics with small x-value exhibited the homogeneous grains. In addition, the small amount of secondary phase Zn 2 TiO 4 exhibited high Qf-value of 19,000 GHz [25]. Therefore, the high Qf value was achieved when x was not above 0.20.…”

A new temperature stable microwave dielectric ceramics: ZnTiNb2O8 sintered at low temperatures

“…1(c), we observed that peak intensity of the Zn 0.17 Nb 0.33 Ti 0.5 O 2 phase increased gradually with increasing TiO 2 content. Zn 0.17 Nb 0.33 Ti 0.5 O 2 has a higher dielectric constant of 95, a Q × f of 15,000 GHz and f = +237 ppm/ • C, in contrast, ZnTiNb 2 O 8 has a lower dielectric constant of 34, a higher Q × f of 42,500 GHz and f = −52 ppm/ • C [4,38]. Consequently, when TiO 2 content increased, the Zn 0.17 Nb 0.33 Ti 0.5 O 2 content increased, so the Q × f values of the compounds decreased gradually due to the relatively lower Q × f value of the Zn 0.17 Nb 0.33 Ti 0.5 O 2 ceramics as 15,000 GHz and the dielectric constants ε r increased gradually due to its higher dielectric constant of 95.…”

“…ature of ZnTiNb 2 O 8 ceramics was above 1200 • C, which is too high to be applicable to LTCC [4,5]. And many researchers have developed several approaches to reduce the sintering temperature of the ceramics: (i) the usage of small particle sized starting materials synthesized by wet chemical methods such as the sol-gel and coprecipitation methods and (ii) the addition of low-melting glasses, oxide or mixed-oxide additives, such as ZnO-B 2 O 3 -SiO 2 (ZBS), Li 2 [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Liquid phase low temperature sintering of niobate and cerate fine powders

“…The effect of T s reduction by CuO/V 2 O 5 dopant is usually attributed to the liquid phase sintering due to the appearance of eutectic melt in this system at the temperatures as low as 630 • C. Zn 3 Nb 2 O 8 is another perspective microwave dielectric material with lower values of dielectric constant (ε r = 22 − 23) and higher maximum values of Q × F (up to 80 000 GHz). Sintering of the undoped coarse-grained Zn 3 Nb 2 O 8 is performed at 1100-1250 • C [9,10] while the introduction of 2% V 2 O 5 into starting mixture allows to reach the density over 95% and Q × F ∼ 60 000 GHz at T = 850 • C [11]. Another complex Zn-Nb oxide, ZnNb 2 O 6 , also demonstrates similar dielectric properties after sintering at T s = 1100-1200 • C. The sintering temperatures can be reduced down to 900 • C by using CuO/V 2 O 5 sintering aids.…”