Structures, Phase Transformations, and Dielectric Properties of BiTaO₄ Ceramics

Abstract

Low (α)- and high-temperature (β) forms of BiTaO have attracted much attention due to their dielectric and photocatalytic properties. In the present work, a third form, the so-called HP-BiTaO, was synthesized at high temperature and pressure. The phase evolution, phase transformations, and dielectric properties of α- and β-BiTaO and HP-BiTaO ceramics are studied in detail. β-BiTaO ceramics densified at 1300 °C with the microwave permittivity ε ≈ 53, the microwave quality factor Q ≈ 12070 GHz, and the temperature coefficient of resonant frequency τ ≈ -200 ppm/°C. HP-BiTaO ceramics were synthesized at 5 GPa and 1300 °C followed by annealing at 600 °C. In contrast with the α phase, HP-BiTaO exhibited ε ≈ 195 at 1 kHz to 10 MHz, accompanied by a low dielectric loss of ∼0.004. The relation between structure and dielectric properties is discussed in the context of Shannon's additive rule and bond theory.

Usage of P–V–L bond theory in studying the structural/property regulation of microwave dielectric ceramics: a review

“…Up to now, several theories have been developed to study the regulation between crystal structure and dielectric pro-perties. For example, THz time-domain spectroscopy and farinfrared reflectance spectroscopy can be used to analyse the intrinsic properties of the lattice vibration of material systems; [28][29][30][31] the Clausius-Mossotti equation predicts the macroscopic dielectric constant of an ionic crystal by using ionic polarizabilities; 32,33 bond-valence theory gives the actual valence state of ions in a crystal structure and provides the basis for the state of the ions. [34][35][36][37] These concepts help researchers gain better insights into the relationship between crystal structure and dielectric properties.…”

BiVO4based highkmicrowave dielectric materials: a review

“…Rutile TiO2, perovskite CaTiO3 and SrTiO3 are three archetype ceramics with highr, high Qf values and large positive TCF values. 166-169 However, high r microwave dielectric ceramics with large negative TCF are rare and all -ve TCF materials with − 200 ppm/ o C are also listed inTable 2 [170][171][172][173]. Among them, BiVO4 is attractive due to its high Qf and low sintering temperature.…”

Synthesis of Zn0.5Ti0.5NbO4 microwave dielectric ceramics with Li2O‐B2O3‐SiO2 glass for LTCC application

“…Fabrication of ceramics usually requires high sintering temperature (>1000°C), such as the commercial microwave dielectric materials of BaO‐TiO 2 (densification of BaTi 4 O 9 demands a high temperature of 1300°C), Ba(Zn 1/3 B 2/3 )O 3 (sintering temperature of 1500°C‐1650°C for B = Nb, 1500°C for B = Ta), and their suitable temperatures exceed 1300°C, which is very energy‐consuming. For the sake of conserving energy, low‐temperature co‐fired ceramic (LTCC) technology emerges as the time requires, besides, LTCC plays an important role in passive integration, reducing circuit dimension, which can improve the flexibility of the design of circuits, however, LTCC application demands a low sintering temperature for the co‐firing with Ag and Cu electrodes (melting point of Ag, Cu is 961°C and 1083°C, respectively), the materials should also maintain great microwave dielectric properties, such as Bi 2 O 3 ‐TiO 2 ‐V 2 O 5 , Bi‐Li‐Ta, and BiVO 4 ‐LaNbO 4 system studied by Zhou, the sintering temperature of ceramic can be decreased to 800°C and still maintain great properties …”

“…For the sake of conserving energy, low-temperature co-fired ceramic (LTCC) technology emerges as the time requires, besides, LTCC plays an important role in passive integration, reducing circuit dimension, which can improve the flexibility of the design of circuits, however, LTCC application demands a low sintering temperature for the co-firing with Ag and Cu electrodes (melting point of Ag, Cu is 961°C and 1083°C, respectively), the materials should also maintain great microwave dielectric properties, such as Bi 2 O 3 -TiO 2 -V 2 O 5 , Bi-Li-Ta, and BiVO 4 -LaNbO 4 system studied by Zhou, the sintering temperature of ceramic can be decreased to 800°C and still maintain great properties. 2,[7][8][9][10][11][12][13] Zn 0.5 Ti 0.5 NbO 4 (ZTN) ceramics with a a-PbO 2 -related ixiolite structure has been studied due to its appropriate dielectric constant (e r , 34~38), high quality factor (Q9f, 35000~40000 GHz) and relative low sintering temperature (1100°C~1200°C). [14][15][16] The sintering temperature is still too high, which restricts its practical use in the LTCC field, therefore, many studies have been implemented to form pure ZTN phase at a sintering temperature lower than 1000°C.…”