Lattice evolution and microwave dielectric properties of La‐doped yttrium aluminum garnet ceramics

Abstract

In this study, Y3−xLaxAl5O12 (0 ≤ x ≤ 0.09) ceramics were synthesized, and the phase composition, lattice evolution, and microwave dielectric properties were investigated in detail. Scanning electron microscopy confirms that the addition of moderate amounts of La2O3 improves the grain development of YAG ceramics, but excessive doping destabilizes the crystal structure. Transmission electron microscopy characterization shows that the variation of the dielectric properties of the samples with x‐value is related to the occurrence of benign dislocation structures caused by modifications in the type and content of the A‐site rare‐earth ions. The variations in relative density, dielectric constant, and quality factor remain basically coordinated. The optimum microwave dielectric properties of La3+ doped YAG samples are exhibited as εr = 10.61, Q × f = 187, 542 GHz, τf = −31.2 ppm/°C when La2O3 is doped at x = 0.015.

Acceleration of optimizing the dielectric properties of (Ca0.7Nd0.2)1−x(Li0.5Nd0.5)xTi1−y(Mg1/3Nb2/3)yO3 with the aid of machine learning

“…In addition to the requirement for a high dielectric constant, other two key properties of the ceramics in the GHz frequency range are also highly concerned: a high quality factor ( Q × f , Q is approximately equal to 1/tan δ ) to improve selectivity and a near‐zero temperature coefficient of resonance frequency ( τ f ) to achieve temperature stability (most microwave devices applications require τ f ≤ ±10 ppm/°C) 5 . Previous studies have shown that even small variations in composition can dramatically affect the dielectric properties of ceramics, 6–8 suggesting the significant challenge of identifying the optimal composition for achieving the desired properties. Meanwhile, researchers have also noted the coupling relationship among ε r , Q × f , and τ f 9 .…”

Investigation of theoretical infrared spectra on microwave dielectric properties of Re2O3 (Re = Ho, Er, Tm) ceramics

“…In addition, rare earth oxides have been widely used in various fields due to their special electronic configurations and physicochemical properties 19–22 . Furthermore, microwave dielectric ceramics containing rare earth oxides had been intensively studied to explore promising microwave dielectric materials 23–26 . In this study, Re 2 O 3 (Re = Ho, Er, Tm) ceramics had been successfully prepared by solid‐phase reaction method, and the intrinsic influence mechanism of the microwave dielectric properties had been investigated using theoretical infrared spectra calculated by first‐principles.…”

“…[19][20][21][22] Furthermore, microwave dielectric ceramics containing rare earth oxides had been intensively studied to explore promising microwave dielectric materials. [23][24][25][26] In this study, Re 2 O 3 (Re = Ho, Er, Tm) ceramics had been successfully prepared by solid-phase reaction method, and the intrinsic influence mechanism of the microwave dielectric properties had been investigated using theoretical infrared spectra calculated by first-principles. Meanwhile, phonon spectra, density of states, and electronic localization functions were calculated together to analyze the dynamical stability and electronic structure of Re 2 O 3 (Re = Ho, Er, Tm) ceramics.…”