Crystallization behavior and microwave dielectric characteristics of ZnO-(La, Nd)2O3-B2O3-based dielectrics

Crystallizable zinc borate glasses modified with different contents of La2O3 or Nd2O3 were investigated as a potential low loss dielectric with respect to their crystallization behavior and microwave dielectric characteristics. The glasses were admixed with Al2O3 filler and fired at 850°C for 30 min in air to prepare low temperature dielectrics. Crystallization behavior and microwave dielectric properties of the resulting samples strongly depended on the relative content of La2O3 or Nd2O3 in the glass. As a promising result, the composition of 0.15ZnO-0.25Nd2O3-0.6B2O3 exhibited k ∼ 6.5 and Q ∼ 1194 at the resonant frequency of 18.9 GHz. Near zero temperature coefficient of frequency (TCF) was obtained by additional modification of the composition with ∼10 wt.% of TiO2 filler. Crystallization kinetics of the samples was studied based on the differential thermal analysis (DTA) curves obtained with different heating rates. Correlation of the observed dielectric properties to the crystallization behavior is the main subject of this work.