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

Abstract

Crystallizable zinc borate glasses modified with different contents of La 2 O 3 or Nd 2 O 3 were investigated as a potential low loss dielectric with respect to their crystallization behavior and microwave dielectric characteristics. The glasses were admixed with Al 2 O 3 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 La 2 O 3 or Nd 2 O 3 in the glass. As a promising result, the composition of 0.15ZnO-0.25Nd 2 O 3 -0.6B 2 O 3 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 TiO 2 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.

Barium Neodymium Titanium Borate Glass‐Based High k Dielectrics

“…A higher heating rate generally tends to show a higher crystallization temperature. Our previous work, as an example, showed the crystallization peak temperature of ~880°C at 3°C/min and ~935°C at 7°C/min in the DTA run of a highly crystallizable 15ZnO·25Nd 2 O 5 ·60B 2 O 3 glass combined with 50 wt% alumina. In this regard, similar to other highly crystallizable glasses, the densification of glass studied herein is also assumed to be affected by crystallization.…”

“…Even though the loss values are quite low, the gradual decrease of the loss was clearly found with increase in the content of either filler. It is interesting to note the decreasing tendency because a higher porosity generally induces a higher dielectric loss . It is assumed that dielectric loss of the current material system is more sensitive to the crystalline phases at each filler level than the level of porosity.…”

“…Two common choices of ceramic filler, that is, Al 2 O 3 and BaTiO 3 , have been chosen. Al 2 O 3 is known as the most common filler for generating LTCC materials targeting a low dielectric constant below ~8.5 over the extended frequency range up to a few tens of GHz . On the other hand, BaTiO 3 is an easily available choice for generating higher k materials even though BaTiO 3 itself is not appropriate for applications at microwave frequency of greater than GHz.…”

Low Temperature Sintering and Dielectric Properties of Alumina‐Filled Glass Composites for LTCC Applications

“…Aluminum oxide (Al 2 O 3 ) has been identified as the first choice for preparation of most of the LTCC materials due to its cost effectiveness, easy availability with a wider choice of particle size and size distribution, and its low reactivity with the glass matrices. Several authors used Al 2 O 3 as a nucleating agent for glass–ceramic systems and also as a filler for the glass + ceramic composites . Fang and Jean studied the effect of particle size on the densification of K 2 O–CaO–SrO–BaO–B 2 O–SiO 2 glass using Al 2 O 3 with particle sizes of 0.05, 0.3, 1.5, 3.0 μm .…”