Microwave dielectric properties of BiVO4/Li0.5Re0.5WO4 (Re = La, Nd) ultra-low firing ceramics

Abstract

A series of dense ceramic samples in the (1 -x)BiVO 4 -xLi 0.5 Re 0.5 WO 4 (Re = La, Nd; 0.05 B xB 0.11) has been prepared by using the traditional solid state reaction method. A single solid solution phase with monoclinic structure is formed through the entire compositions and the unit cell volume increases linearly with x. When x = 0.09, the composition of 0.91BiVO 4 -0.09 Li 0.5 La 0.5 WO 4 readily sintered at 750°C shows good microwave properties with e r of 76.7, Q 9 f of 6789 GHz and s f of 7.3 ppm/°C. As x = 0.08, the 0.92BiVO 4 -0.08Li 0.5 Nd 0.5 WO 4 ceramic sintered at 750°C possesses excellent microwave dielectric properties of e r = 71.8, Q 9 f = 7482 GHz and s f = 0.8 ppm/°C. These ceramics have applications for microwave devices requiring high permittivity and ultra-low sintering temperature.

Temperature Stable Cold Sintered (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 Microwave Dielectric Composites

“…For miniaturization and reliability, microwave devices are fabricated from Low/Ultra-Low Temperature Co-fired Ceramics (LTCC and ULTCC) due to their compatibility with sustainable and cheap electrodes such as Ag, Cu and Al [2,3,4,5,6]. Typically, MW ceramics have permittivity, 10 < ε r < 100, and quality factor, 2000 < Qf < 200,000, depending on the precise application along with near-zero Temperature Coefficient of resonant Frequency (TCF < ±10 MK −1 ) [7,8,9,10,11,12]. Dielectric resonators require ultra-high Qf (>40,000 GHz) and medium permittivity (20 < ε r < 50) whereas LTCC typically have low ε r (~10) and require only moderate Qf (~2000) for 3/4G mobile technology [7,8,9,10,11,12].…”

Cold-Sintered Temperature Stable Na0.5Bi0.5MoO4–Li2MoO4 Microwave Composite Ceramics

“…Microwave (MW) dielectric ceramics are widely used in modern wireless communication systems in applications such as resonators, filters and capacitors . To meet the requirement of miniaturization and reliability of microwave devices, low/ultralow temperature ceramics have attracted interest due to their compatibility with low cost electrodes such as Ag, Cu and Al. − Typically, MW ceramics not only require a higher permittivity, 15 < ε r < 100, and a large MW quality factor ( Q × f > 5000) depending on the application but also a near-zero temperature coefficient of resonant frequency (TCF). − …”

“…Although there are several low temperature ceramics fabricated through conventional sintering with near zero TCF, − no cold sintered materials have been shown to be temperature stable. In this work, Na 0.5 Bi 0.5 MoO 4 (NBMO, +43 ppm/°C) and Li 2 MoO 4 (LMO, −160 ppm/°C) ceramics are selected as end-members in a composite series, predicted to achieve zero TCF. , NBMO-LMO composite ceramics were fabricated using cold sintering and their microwave dielectric properties adjusted continuously as a function of the weight fraction of LMO to achieve zero TCF.…”