Influence of P2O5 and SiO2 addition on the phase, microstructure, and electrical properties of KNbO3

TL;DR

This study investigates how adding P2O5 and SiO2 affects the phase, microstructure, and electrical properties of KNbO3 ceramics, revealing improved densification and notable dielectric property variations.

Contribution

It provides new insights into how P2O5 and SiO2 additions influence sintering behavior, microstructure, and electrical properties of KNbO3, with specific effects on densification and dielectric performance.

Findings

P2O5 acts as a sintering aid, reducing sintering temperature by about 30°C.

SiO2 addition slightly increases grain size with higher sintering temperatures.

Dielectric constant and loss tangent vary significantly with additive type and frequency.

Abstract

In this contribution, the effect of P2O5 and SiO2 addition on the phase, microstructure, and electrical properties of KNbO3 was studied. Sample powders with the general formula (1-x)KNbO3.xP2O5 (x = 0.03, 0.05) and (1-x)KNbO3.xSiO2 (x = 0.1) were prepared via mixed-oxide route. The thermal behavior of the mixed-milled powder was investigated by TG/DTA which revealed an overall weight loss of 33.4 wt % in the temperature range of 30 < T < 1200 C and crystallization exotherm occurring at about 795 C. The present results indicated that P2O5 acted as a sintering aid and lowered the sintering temperature by about 30 C and promoted densification of KNbO3. Sample compositions at various stages of processing were characterized using X-ray diffraction. Samples sintered at T < 1020 C revealed mainly KNbO3 together with a couple of low-intensity K3NbO4 peaks as a secondary phase. The SEM images of (1-x)KNbO3.xSiO2 (x = 0.1) samples showed a slight increase in the average grain size from 3.76 um to 3.86 um with an increase in sintering temperature from 1000 C to 1020 C. Strong variations in dielectric constant and loss tangent were observed due to P2O5 and SiO2 addition as well as frequency of the applied AC signals.