High-Temperature Capacitance Stability and Insulating Properties of PNb9O25 Synthesized via Liquid-Phase Sintering: Strategic Utilization of Glass-Oxide Interfacial Reactions

High-performance dielectric materials are essential for production of electrical storage capacitors used in electric vehicles, solar converters, and aerospace power conditioning applications where power systems and electronic devices must operate reliably at elevated temperatures. This study investigates PNb 9 O 25 as a high-temperature dielectric material and reports our liquid-phase sintering method that utilizes interfacial reactions between SiO 2 –P 2 O 5 glasses and Nb 2 O 5 to form PNb 9 O 25 with SiO 2 -rich amorphous boundaries. The synthesized SiO 2 –PNb 9 O 25 composites show a denser microstructure than PNb 9 O 25 synthesized through the solid-state reaction. PNb 9 O 25 synthesized via our liquid-phase sintering approach exhibits a high dielectric constant (376), superior high-temperature capacitance stability (within ±15% up to 300 °C), and low electrical conductivity (≤ 10 −7 S cm −1 below 300 °C). These high-temperature capacitance stability and insulating properties are attributed to its amorphous–crystalline microstructure, where SiO 2 –rich amorphous phase performs multiple functions, including the suppression of grain growth and oxygen-vacancy formation. SiO 2 –PNb 9 O 25 composites synthesized using our liquid-phase sintering method are promising materials for high-temperature dielectric applications.