Low‐Temperature, Single Step, Reactive Sintering of Lead Magnesium Niobate Using Mg(OH)₂‐Coated Nb₂O₅ Powders

Abstract

A low‐temperature, single step, reactive sintering method for Pb(Mg1/3Nb2/3)O3 (PMN) and PMN–PbTiO3 (PMN–PT) processing was developed based on the coating of Mg(OH)2 on Nb2O5. This method simplified the processing of PMN and PMN–PT to a single step of heat‐treatment and decreased the sintering temperature to 1000°C. It was found that the pyrochlore phase formation reaction at 500°C reduced the particle size to 130 nm. The overlap of the pyrochlor‐perovskite phase transformation between 700° and 900°C and the densification process between 800° and 1000°C improved the sintering process. These two factors were the major reasons of the low temperature sintering.

Synthesis of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 by Controlled Agglomeration of Precursor Particles

“…Gu et al . coated the Nb 2 O 5 particles with Mg(OH) 2 to prevent physical contacts between niobium and lead oxide particles, and thereby hinder the formation of pyrochlore phases …”

“…18 Gu et al coated the Nb 2 O 5 particles with Mg(OH) 2 to prevent physical contacts between niobium and lead oxide particles, and thereby hinder the formation of pyrochlore phases. 19,20 Recently, our group has introduced a new approach to the synthesis of Pb(Mg 1/3 Nb 2/3 )O 3 with the controlled agglomeration of precursor particles. 21 The structure of the self-assembled colloidal agglomerates in the suspension of PbO, Nb 2 O 5 , and (MgCO 3 ) 4 ·Mg(OH) 2 ·4H 2 O (MHC) has a major influence on the synthesis of the PMN.…”

Synthesis of Pb(Mg1/3Nb2/3)O3 by Self‐Assembled Colloidal Aggregates

“…synthesized pyrochlore‐free PMN‐PT powders by introducing polyethylene glycol in the conventional solid‐state reaction. An alternative route for the PMN synthesis is a single‐step calcination method where Mg(OH) 2 ‐coated Nb 2 O 5 particles were prepared in the first step, then mixed with PbO, and calcined to yield the perovskite phase 17,18 . PMN ceramics were also synthesized from an aqueous suspension, however, without any details on the synthesis conditions 19…”

Double Precursor Solution Coating Approach for Low‐Temperature Sintering of [Pb(Mg1/3Nb2/3)O3]0.63[PbTiO3]0.37 Solids

“…Without such assistance, sintering of lead‐based relaxor or ferroelectric ceramics typically requires temperatures well above 1000°C with a lead‐rich atmosphere provided by adding trace amount of excess lead oxide (PbO) or by burying the samples in similar lead‐containing powders in (double) crucibles to prevent lead loss 7 . A more recent achievement in lowering the sintering temperature of PMN–PT without other aids was a single‐step sintering method where Mg(OH) 2 ‐coated Nb 2 O 5 particles obtained with an aqueous coating approach 8 were mixed with commercial PbO and lead titanate powder and directly sintered at 1000°C in air 9 . The low sintering temperature was due to the formation of perovskite PMN–PT around 900°C in the compact at which sintering also took place.…”

“…7 A more recent achievement in lowering the sintering temperature of PMN-PT without other aids was a single-step sintering method where Mg(OH) 2 -coated Nb 2 O 5 particles obtained with an aqueous coating approach 8 were mixed with commercial PbO and lead titanate powder and directly sintered at 10001C in air. 9 The low sintering temperature was due to the formation of perovskite PMN-PT around 9001C in the compact at which sintering also took place. Because the reactions in that study were between micrometer-sized particles, it is possible to further lower the sintering temperature by more intimately mixing the PT or PbO with the Mg(OH) 2 -coated Nb 2 O 5 particles using nanosized PT or PbO particles.…”