Novel MgHf₄P₆O₂₄ as a Solid Electrolyte in Mg-Sensors

Abstract

In this paper, the electrochemical impedance analysis of MgHf4P6O24 electroceramic oxide electrolyte on platinised pellets of 13mm diameter (Ø) and 3.8mm thickness depicts the electrical properties of Mg 2+ -cation conducting species in the characterised solid-state electrolytes measured using the two-probe analysis at 182-764 o C, and from 100mHz to 32MHz, were evaluated. In this analysis, promising ionic conductivity of 4.52 x 10 -4 Scm -1 for MgHf4P6O24 electroceramic electrolyte was exhibited at 747 o C, thereby maintaining both materials and operational stability at 1000 o C ≤ T/ o C≤1300.In addition to this, the design, fabrication and testing of solid-state Mg-sensors using the electrochemical method have been achieved. The novel high-temperature Mg-sensors were designed using the highly conducting Mg 2+ -cation solid-state electrolyte by incorporating a biphasic powder mixture of MgCr2O4 + Cr2O3 solid-state reference electrode, which has shown promising trend after successfully sensing Mg dissolved in molten Al at 700±5 o C.

Improved Ionic Conductivity of MgM4P6O24 (M = Hf, Zr) Ceramic Solid-State Electrolytes by Sol-Gel Synthesis

“…The STA 8000 (PerkinElmer, Seer Green, UK) was used to measure the TGA-DSC, which was later used to analyse the weight loss and thermal oxidation behaviour of the dried xerogel powders. In this measurement, effective optimisation calcination condition of the xerogel powders in a controlled atmosphere at a flow rate of 50 mL min -1 using a constant heating-cooling rate at 10 o C min -1 within a temperature range of 30 -1000 o C, akin to that described in our recent papers (2,9) was established. Based on the data from this measurement, the resultant dried xerogel powders were calcined at 900 o C, and the calcined nanopowders were pelletised and later sintered at 1300 o C, using the same heating-cooling condition.…”

“…Figure 4. Bulk ionic conductivity profiles of MgZr4P6O24 and MgHf4P6O24 solid-state electrolytes as a function of temperature(1,2,9) …”

Improved Ionic Conductivity of MgM4P6O24 (M = Hf, Zr) Ceramic Solid-State Electrolytes by Sol-Gel Synthesis

“…Recently, notable research interest has been drawn towards further investigation and characterisation of MgHf4P6O24 and other phosphate ceramic solid-state electrolytes synthesised using the sol-gel chemical route. Consequently, the sol-gel method was deployed in this study for the synthesis of MgHf4P6O24 and MgZr4P6O24 electrolytes, and because sol-gel chemical synthesis technique has shown the potential to produce very fine homogeneous powders at a relatively low processing temperature, which can be pelletised and sintered into very dense solid-state electrolytes for application in electrochemical impedance spectroscopy measurement (1,9,10).…”

Assessment of Novel MgCe4P6O24 Ceramic Electrolyte in Fabricating Mg-Sensors: Focus on Structure and Electrochemical Impedance Spectroscopy

“…Materials research focused on the sol-gel synthesis and characterisation of structural and electrical properties of the tetravalent B-site oxides has experienced a resurgence of interest in recent years. In particular, tetravalent Zr and Hf ion based ceramic electrolytes have attracted so much attention in the past few years due to their excellent applicability potentials as high-temperature electroceramics in chemical sensors, solid-oxide fuel cells, solid-state batteries and other high-temperature systems (1)(2)(3)(4). The potential application of novel functional materials, such as ceramic electrolytes in sensor fabrication, rechargeable energy sources and storage systems for future vehicles like solid-state multivalent batteries is the signature need for increasing future demands which has culminated in this study of monoclinic MgCe4P6O24 ceramic electrolyte.…”

“…In using appropriate stoichiometric amount of precursor oxides, the most studied representatives of MgZr4(1-x)M4xP6O24 family are MgZr4P6O24 [x = 0] (1,2,4) and MgHf4P6O24 [x = 1, M = Hf] (3,4), with these ceramic electrolytes showing excellent improvements in both the ionic conductivity and thermodynamic stability, which are suitable parameters for identifying the ceramic electrolytes as a divalent Mg ion conductor in fabricating solid-state Mg-sensors (1)(2)(3)(4). In this study however, novel MgCe4P6O24 ceramic electrolyte was synthesised using sol-gel method and characterised to analyse the structure and electrical properties of the ceramic electrolyte.…”