Fabrication, phase formation and microstructure of Ni4Nb2O9 ceramics by using two-stage sintering technique

TL;DR

This study demonstrates that two-stage sintering can produce dense, pure Ni4Nb2O9 ceramics with enhanced ferroelectric properties at relatively low temperatures, optimizing phase purity and microstructure.

Contribution

It introduces a two-stage sintering method to fabricate high-density, single-phase Ni4Nb2O9 ceramics with improved microstructure and ferroelectric behavior.

Findings

Maximum density of 92% achieved at 950/1250°C

Single-phase Ni4Nb2O9 obtained through optimized sintering

Enhanced ferroelectric properties observed in doubly sintered ceramics

Abstract

The potential utilization of two-stage sintering for the production of highly dense and pure nickel diniobate (Ni4Nb2O9) ceramics with low firing temperature was demonstrated. Effects of designed sintering conditions on phase formation, densification and microstructure of the ceramics were characterized by X-ray diffraction (XRD), Archimedes method and scanning electron microscopy (SEM), respectively. It has been found that minor phase of columbite NiNb2O6 tended to form together with the desired Ni4Nb2O9 phase, depending on sintering conditions. The optimization of sintering conditions could lead to a single-phase Ni4Nb2O9 ceramics with orthorhombic structure. The ceramics doubly sintered at 950/1250 {\deg}C for 4 h exhibited maximum density value of 92%. Microstructures with denser angular grain-packing were generally found in both sets of the sintered Ni4Nb2O9 ceramics. However, the grains were irregular in shape when the samples are sintered at 1050/1250 {\deg}C. Two-stage sintering was also found to enhance ferroelectric behavior of Ni4Nb2O9 ceramic.