Microwave and infrared dielectric response of monoclinic bismuth zinc niobate based pyrochlore ceramics with ion substitution in A site

Abstract

Articles you may be interested inEffect of B 2 O 3 -Bi 2 O 3 -SiO 2 -ZnO glass on the dielectric and magnetic properties of ferroelectric/ferromagnetic composite for low temperature cofired ceramic technology Bismuth zinc niobate pyrochlore dielectric thin films for capacitive applications It is well known that the cubic pyrochlore Bi 1.5 ZnNb 1.5 O 7 exhibits higher permittivity and dielectric loss than monoclinic Bi 2 Zn 2/3 Nb 4/3 O 7 due to structural disorder in the A sites of Bi 1.5 ZnNb 1.5 O 7 . We have studied systematically the impact of the ion substitution in the A site of monoclinic Bi 2 Zn 2/3 Nb 4/3 O 7 on the structure and microwave dielectric properties. It is shown that the structure and permittivity of ͑Bi 1.92 M 0.08 ͒͑Zn 0.64 Nb 1.36 ͒O 7 ͑M =Zn,Ca,Cd,Sr,Ba͒ ceramics remain almost the same as in Bi 2 Zn 2/3 Nb 4/3 O 7 ; only the Ba substituted ceramics have higher permittivity due to multiphase structure. Microwave dielectric properties were compared with complex dielectric response in terahertz and infrared frequency range of 0.1-100 THz, which allows us to estimate intrinsic and extrinsic contributions to microwave dielectric losses. The best microwave properties were obtained in ͑Bi 1.92 Ca 0.08 ͒͑Zn 0.64 Nb 1.36 ͒O 7 with = 76, Qf ജ 5000 ͑sintered below 950°C͒, which is promising for microwave low temperature cofiring ceramic application.

Processing of Bi1.5ZnNb1.5O7 ceramics for LTCC applications: Comparison of synthesis and sintering methods

“…The temperature coefficient of capacitance (TCC) for the different samples showed in Table 2 is in agreement with the literature for a-BZN, approximately À400 ppm 8C À1 [2]. …”

“…The driven force for part of those publications is the understanding of their electrical properties depending on the occupancy of metallic cations in sites A and B [1][2][3][4]. The other matter of concern is reducing the sintering temperature of those compounds aiming to make them suitable for LTCC using silver as internal electrode [5][6][7][8].…”

Novel red phosphors Gd2GaTaO7:Eu3+,Bi3+ for white LED applications

“…However, it is difficult to obtain phase pure compounds with this general composition without forming LnMO 4 secondary phase particularly in tantalate system [9]. Wang et al [10] reported the better ordering in the crystal structure when the compounds crystallize into a monoclinic phase than the cubic phase. In ordered host crystal lattice the activator ions could be more uniformly distributed which in turn improves the photoluminescence emission intensity.…”

Effect of Sn4+ and W6+ substitution on the dielectric properties of Bi2O3–ZnO–Nb2O5-based low firing ceramics

“…Previous work revealed that there are two main phases in the system: a cubic pyrochlore phase (a phase) Bi 1.5 ZnNb 1.5 O 7 (e r = 150, tand * 10 -4 , a & -400 ppm/°C) and a monoclinic pyrochlore phase (b phase) Bi 2 Zn 2/3 Nb 4/3 O 7 (e r = 80, tand * 10 -4 , a & ?200 ppm/°C) [6]. Such properties, combined with a low sintering temperature (*1000°C), render these materials as an attractive candidates for LTCC applications in high frequency and microwave range [8][9][10][11]. However, for LTCC applications in multilayer components and further increasing the capacitive volumetric efficiency of embedded components, modifying the temperature coefficient of dielectric constant and further enhancing the dielectric constant are still absolutely necessary.…”