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.