Effects of Crystal Structure on the Microwave Dielectric Properties of ABO₄ (A = Ni,Mg,Zn and B = Mo,W) Ceramics

Abstract

The dependence of microwave dielectric properties on the crystal structure, bond character, and electronic characteristics of AMoO4 and AWO4 (A = Ni, Mg, Zn) ceramics was investigated. The dielectric constant (K) of specimens was principally affected by the dielectric polarizabilities, molar volume, and electronic oxide polarizabilities. MgMoO4 and AWO4 (A = Ni, Mg, Zn) display a single phase monoclinic wolframite structure, whereas ZnMoO4 is a single phase triclinic wolframite structure. The quality factor (Qf) of AWO4 was higher than that of AMoO4 (A = Mg, Zn); these results were attributed to the packing fraction due to effective ionic size. The temperature coefficient of the resonant frequency (TCF) of the specimens was dependent on the cations' bond valence between the cation and oxygen ions. This suggests the ability to tailor ABO4 microwave K, Qf, and TCF via ionic design rules.

Microstructure and microwave dielectric characteristics of (Zn1−xCox)ZrNb2O8 ceramics

“…5. The Qf value mainly depends on extrinsic factors such as density, impurity, secondary phases and grain size, and intrinsic ones such as the packing fraction and the nature of bonding [22]. It is observed from XRD patterns that (Zn 1-x Co x )ZrNb 2 O 8 (x = 0.1, 0.2, 0.3, 0.4) ceramics possess a single-phase.…”

Theoretical and Experimental Study of Structural Phases in CoMoO4†

“…(Figure 2a) Furthermore, we note that the (I)/(II)-phases are supposed to be the low/high temperature modifications, respectively. However, 3 ] of the unit cell, for CoMoO 4 phases observed directly after synthesis (SPRT), and in samples that had been subsequently calcinated at 300, 600, 900 and 1200°C, respectively. The data were obtained using the software package Powder Cell.…”

“…Although there exist a large number of high-quality experimental studies on CoMoO 4 compounds, [1][2][3][4][5][6] there are many open questions regarding individual experimentally observed phases, the α → β phase transition, which phase should be properly denoted α or β, respectively, and the temperature conditions at which they are obtained. [7][8][9][10][11][12][13][14][15] A very important issue is the development of a cost-and-time effective method for the preparation of nanostructured cobalt molybdenum oxide with precise control of particle size.…”

Correlations of crystal structure, bond energy and microwave dielectric properties of AZrNb2O8 (A = Zn, Co, Mg, Mn) ceramics

“…The apparent densities of the sintered pellets were measured use the Archimedes method (Mettler ToledoXS64). To study the relative density of the sample, the theoretical density was obtained from the crystal structure and atomic weight [14].…”