Crystal Chemistry, Raman Spectra, and Bond Characteristics of Trirutile-Type Co_0.5Ti_0.5TaO₄ Microwave Dielectric Ceramics

Abstract

A novel trirutile-type Co0.5Ti0.5TaO4 ceramic was reported here for the first time. The correlations between the sintering behavior, crystal structure, chemical bond, and dielectric properties were investigated. Pure Co0.5Ti0.5TaO4 ceramic was synthesized in the temperature range of 1000–1100 °C. A trirutile structure and refined parameters of a = b = 4.71163 Å, c = 9.13586 Å, and V cell = 202.811 Å3 could be obtained (1075 °C). According to the P–V–L chemical bond theory, majority contributions to the dielectric constant originated from Ta–O bonds, owing to its largest bond ionicity and bond susceptibility values. The experimental dielectric constant is close to the theoretical values calculated via the P–V–L chemical bond theory and Clausius–Mossotti relationship. The Ta–O bonds that present the largest lattice energy are also the main factors influencing the intrinsic loss. The τf value is consistent with the oxygen distortions of the octahedron. More importantly, variations of the densification, average grain size, and grain boundary are crucial factors for development of the microwave dielectric properties. The Raman spectra and group theory were analyzed together, and the results indicated that the A1g mode at 687.45 cm–1, which reflects the stretching vibrations of the O anions, dominates the Raman vibrations. Typical microwave dielectric properties of Co0.5Ti0.5TaO4 ceramics were obtained when sintered at 1075 °C: εr = 40.69, Qf = 17291 GHz, and τf = 114.54 ppm/°C.

Phase evolution, crystal structure, and microwave dielectric properties of gillespite‐type ceramics

“…A high binding energy means that a chemical bond has great stability. Furthermore, the anharmonic lattice vibration and dielectric loss are reduced 54 . The lattice energy of Ba/Sr‐O and Si‐O bonds shows an increasing trend, which is similar to that of U cal .…”

Gd2Zr3(MoO4)9 microwave dielectric ceramics with trigonal structure for LTCC application

“…Nevertheless, after the temperature higher than the optimal sintering temperature (725°C), the abnormal grain growth would lead to excessive grain size. This phenomenon makes the uniformity of microstructure broken and results in a relatively lower density, which inevitably has negative influence on microwave dielectric properties …”

“…This theory provided a possibility for quantifying contributions of basic variables such as chemical bond lengths, average number of valence electrons per bond to variations of dielectric characterization. Indeed, for niobate and tantalite, P‐V‐L theory has been regarded as feasible method to identify correlation of bond characteristic and properties. Considering the complex framework and crystal information, binary molybdate Gd 2 Zr 3 (MoO 4 ) 9 is written as follows:…”

“…This phenomenon makes the uniformity of microstructure broken and results in a relatively lower density, which inevitably has negative influence on microwave dielectric properties. [29][30][31] Intrinsically, the functional dependence of microwave dielectric properties on bond characteristics has been developed by Levine (P-V-L theory), where the basic dielectric description proposed by Phillips and Van Vechten (P-V) is extended to complex crystal. 32 This theory provided a possibility for quantifying contributions of basic variables such as chemical bond lengths, average number of valence electrons per bond to variations of dielectric characterization.…”

Vibrational spectroscopic and crystal chemical analyses of double perovskite Y2MgTiO6 microwave dielectric ceramics

“…In this regard, Zhou et al verified that Raman spectroscopy was a crucial technique to identify phase composition and phase evolution . Relevant Ruddlesden‐Popper structures and trirutile‐type Co 0.5 Ti 0.5 TaO 4 were designed, and crystalline information and intrinsic microwave dielectric characteristics were investigated through vibrational mode analysis.…”