Solid electrolytes based on {1 (x + y)}ZrO2-(x)MgO-(y)CaO ternary system: Preparation, characterization, ionic conductivity, and dielectric properties

Different composition of composite material of zirconium dioxide co-doped with magnesium oxide [MgO (x)] and calcium oxide [CaO(y)] according to the general molecular formula {1 (x + y)}ZrO2-(x)MgO-(y) CaO were prepared by co-precipitation method and characterized by different techniques, such as XRD, FTIR, TG-DTA, and SEM. Co-doping was conducted to enhance the ionic conductivity, as mixed system show higher conductivity than the single doped one. Arrhenius plots of the conductance revealed that the co-doped composition ‘‘6Mg3Ca” has a higher conductivity with a minimum activation energy of 0.003 eV in temperature range of 50–190 C. With increasing temperature, dielectric constant value increased; however, with increasing frequency it shows opposite trend. Co-doped composition C2 exhibit higher conductivity compared to C3, owing to the concentration of Mg content (0–6%); the conductivity decreases thereafter. Zirconium oxide was firstly used for medical purpose in orthopaedics, but currently different type of zirconia-ceramic materials has been successfully introduced into the clinic to fix the dental prostheses.

Journal of Advanced Research (2018) 35–41 Contents lists available at ScienceDirect Journal of Advanced Research journal homepage: www.elsevier.com/locate/jare Original Article Solid electrolytes based on {1 À (x + y)}ZrO2-(x)MgO-(y)CaO ternary system: Preparation, characterization, ionic conductivity, and dielectric properties Nazli Zeeshan, Rafiuddin ⇑ Physical Chemistry Division, Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 30 May 2017 Revised October 2017 Accepted 16 October 2017 Available online 17 October 2017 Keywords: ZrO2-MgO-CaO system Synthesis Characterization Impedance spectroscopy Ionic conductivity Dielectric properties a b s t r a c t Different composition of composite material of zirconium dioxide co-doped with magnesium oxide [MgO (x)] and calcium oxide [CaO(y)] according to the general molecular formula {1 À (x + y)}ZrO2-(x)MgO-(y) CaO were prepared by co-precipitation method and characterized by different techniques, such as XRD, FTIR, TG-DTA, and SEM Co-doping was conducted to enhance the ionic conductivity, as mixed system show higher conductivity than the single doped one Arrhenius plots of the conductance revealed that the co-doped composition ‘‘6Mg3Ca” has a higher conductivity with a minimum activation energy of 0.003 eV in temperature range of 50–190 °C With increasing temperature, dielectric constant value increased; however, with increasing frequency it shows opposite trend Co-doped composition C2 exhibit higher conductivity compared to C3, owing to the concentration of Mg content (0–6%); the conductivity decreases thereafter Zirconium oxide was firstly used for medical purpose in orthopaedics, but currently different type of zirconia-ceramic materials has been successfully introduced into the clinic to fix the dental prostheses Ó 2017 Production and hosting by Elsevier B.V on behalf of Cairo University This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Introduction Peer review under responsibility of Cairo University ⇑ Corresponding author E-mail address: rafiuddin.chem11@gmail.com (Rafiuddin) The problem associated with liquid electrolytes in practical applications, such as leakage, low energy, limited operating tem- https://doi.org/10.1016/j.jare.2017.10.006 2090-1232/Ó 2017 Production and hosting by Elsevier B.V on behalf of Cairo University This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) 36 N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 perature range, and low power density are removed by solid form of electrolytes [1] Solid electrolytes have become a widely studied field of solid state chemistry in recent years, due to their excellent suitability as electrically conductive material at high temperature The most used solid electrolyte or fast ion conductor at present are those where oxygen ions are the charge carriers; namely oxide ion conductors Oxide ion conductors aroused worldwide attention for its wide application domains as chemical sensor, solar cells, and oxygen separation membrane and in SOFCs [2] The classical ion conducting oxide material are those based on ZrO2, CeO2 and ThO2 Recently, doped ZrO2 was the most studied solid ionic conductor, because of its attractive anionic conductivity, as well as good thermal stability At room temperature, zirconium dioxide has a monoclinic structure, which undergoes transformation as the temperature increases From 1170 °C to 2370 °C, zirconia has tetragonal modification whereas at a temperature higher than 2370 °C, it adopts cubic structure [3,4] Pure zirconia is basically a poor oxide ion conductor at lower temperature Therefore, researchers are concentrating to develop a new material where high temperature ZrO2 cubic/tetragonal (high ionic conductivity) phases stabilized at lower temperature by doping [5] It was observed that the stability of the high temperature modifications of zirconia with oversized divalent or trivalent cation dopants (such as Y3+, Ca2+, Mg2+, Ce3+) was much higher than that of undersized trivalent cation (such as Al3+, Fe3+ and Cr3+) dopants Thence, cations used as dopant for stabilization of zirconia must have a large ionic size and lower charge state than Zr [6] The effect of the dopant oxide on the ionic conductivity of ZrO2 based ternary system has been investigated extensively It was reported that mixed oxides produced material with superior properties than single component [7–10] Therefore co-doping was carried out using suitable fluorite stabilizer oxide (MgO, CaO, Y2O3, and CeO2) to improve stability as well as promoting the formation of defects In the present investigation, calcium and magnesium oxides are chosen as a dopant; not only because they are relevant to the oversized cations and are of lower charge state but also they are cheap precursors [6] For doping of zirconium dioxide, different methods, such as co-precipitation [11] alkoxides [12], citrate routes, and powder mixing [13] are used The present study reports the synthesis of CaO/MgO doped Zirconia and its characterization using various analytical techniques Experimental Synthesis of zirconium dioxide was carried out using zirconium oxychloride (CDH, New Delhi, India) by co-precipitation method Weighed amount of zirconium oxychloride (ZrOCl2Á8H2O) was reconstituted in distilled water and stirred well After obtaining homogeneous solution, precipitation was conducted by adding 100 mL of NaOH The obtained precipitate was washed several times with distilled water until it become neutral and then placed in oven for drying at 200 °C for h The obtained raw material was grinded in an agate mortar in the medium of acetone with intermittent grinding into fine powder and heat at 800 °C for 24 h For synthesis of Mg and Ca doped zirconia, requisite amount of precursors zirconium oxychloride, magnesium nitrate (Merck, Mumbai, India), and calcium nitrate (Otto Kemi, Mumbai, India) were dissolved in water and the above described procedure was carried out [14] The X-ray diffraction data of the resultant material were collected in the range of 20 2h 80° using Bruker AXD D8 X-ray diffractometer with Cu Ka radiation (k = 1.5406 °A) at room temperature for confirming the desired phase of samples Scanning Electron Microscope (JEOL JSM-6510 LV) was used to evaluate the surface morphology features at an accelerating rate of 20 kV The thermal decomposition of synthesized material was analysed through thermo-gravimetric and differential thermal analysis (TG/DTA) using ‘‘PerkinElmer Thermal Analyser” with heating rate of 20 °C minÀ1 from the temperature range of 40–800 °C in nitrogen flowing atmosphere FTIR analysis was conducted by ‘‘Perkin Elmer Spectrum Version 10.4.00” in the wavelength range of 4000–400 cmÀ1 at room temperature The finally obtained fine powder was pelletized by applying pressure of tons cmÀ2 The prepared circular pellet has the radius 0.65 cm and thickness 0.1 cm Before performing the electrical and dielectric measurements, opposite surfaces of the pelletized sample were coated by carbon paste to ensure good electrical contact with electrode capacitor The temperature dependent electrical conductivity and dielectric measurements of the sample have been performed using a Wayne Kerr ‘‘43100” LCR meter from 30 °C to 1000 °C temperature range The heating rate of the sample was controlled by Eurotherm C1000 [15] Different compositions of material used in this study are presented in Table Results and discussion The purity and phase crystallinity of the prepared composite samples were confirmed by XRD analysis The representative XRD patterns of synthesized material by co-precipitation method and annealed at 800 °C for 24 h was shown in Fig It can be clearly seen from the Fig that two phase nature of the composite has been obtained and doping of MgO and CaO has no effect on the peak position, rather it only affects the peak height of pure zirconia Phase composition analysis reveals that pure ZrO2 (C0) show co-existence of monoclinic and tetragonal phase; the monoclinic phase concentration was more than that of tetragonal phase The observed diffraction pattern of pure ZrO2 having tetragonal crystal structure with lattice constant a = 0.35644 Å, c = 0.5176 Å and monoclinic phase with lattice cell parameter a = 0.5144 Å, b = 0.51964 Å and c = 0.51964 Å [16] Additionally some new peaks detected in case of composite diffractograms (C1, C2 and C3) have a lattice constant a = b = c = 0.4195 Å, which allocates the presence of cubic structure of MgO [17] After co-doping of zirconia with CaO and MgO (C2, C3), monoclinic phase of zirconia become the minor one and the high temperature cubic phase whose intensity increases as the doping level of CaO increases is the dominating one with same position of peak However, the peaks of sample C4 become broad with increasing concentration of CaO and fully cubic stabilized zirconia ceramics was obtained after addition of 12 mol% CaO That was due to the decrease in grain size Along with cubic phases, at 2h = 31.29° and 45.15°, extra peaks of CaZrO3 are also observed [6] FTIR spectra for pure and composite samples were presented in Fig The observed strong absorption peak at approximately 452 cmÀ1 region is due to ZrAO vibration, which confirmed the formation of ZrO2 structure; prominent peak at 1383 cmÀ1 corresponds to the OAH bonding The peak at 1621 cmÀ1 may be due to adsorbed moisture and broad band around 3346–3433 cmÀ1 are due to stretching vibrations of the OAH bond of water molecules [18,19] Further, composition C1, C2, C3, and C4 have some new IR bands at different wave numbers corresponding to MgO and CaO content The absorption peaks at 1635 cmÀ1 and 1137 cmÀ1, 1012 cmÀ1 of spectra C1, C2, C3 correspond to bending vibration of OH bonds and MgAOH stretching vibration, respectively The peaks around 833–617 cmÀ1 were assigned to different MgAOAMg vibration modes of MgO [20,21] The peak at 595 cmÀ1 is associated with the vibration of CaAO bonds The transmission peak in spectra of C2, C3, and C4 located at 876 cmÀ1 is related to symmetric stretching vibration of CaAOACa bonds The sharp 37 N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 Table The nominal composition of the investigated samples Sample ZrO2 8Mg 6Mg3Ca 4Mg6Ca 12Ca Composition (mol%) ZrO2 MgO CaO Sample denotation 100 92 91 90 88 0 12 C0 C1 C2 C3 C4 Fig X-ray diffraction patterns for the C0, C1, C2, C3, C4 composite solid electrolyte Fig FTIR spectra for the C0, C1, C2, C3, C4composite solid electrolytes and intense peak at 1410 cmÀ1 was assigned to the asymmetrical stretching vibration of OHACa [22] The DTA curves for pure ZrO2 and its composite were illustrates in Fig The thermogram of pure ZrO2 indicates a broad endothermic peak at temperature 70 °C, which is due to evolution of absorbed water from the prepared powder With increase in temperature, sharp exothermic peak was observed at 475 °C that was related to the lower temperature phase transition of pure ZrO2 to tetragonal/cubic phase (high temperature phases) However, for Fig DTApeaks of the C0, C1, C2, C3, C4 composite solid electrolyte doped samples the intensity of exothermic peaks increases and peaks shifts to higher temperature, the shift increases with increase in conductivity [23–25] Electron microscopy is a versatile tool capable of providing structural information over a wide range of magnification SEM micrograph of undoped and doped zirconia samples prepared via co-precipitation method was shown in Fig The SEM image (a) of pure zirconia clearly demonstrate that powder consist of irregular shape agglomerates covered by smaller particles [26] After substitution of Mg to ZrO2, smooth and uniform surface was obtained It can be seen clearly from the image that magnesium oxide has been mixed properly with zirconium dioxide phase and form a homogeneous mixture The particles are closely packed together and form hard agglomerates on addition of Ca and therefore conductivity of the composite decreases, within the grains formation of isolated micro pores were also observed [27] The EDX spectra of (b) and (c) indicate the presence ZrO2, MgO, and CaO, however existence of Cl was also noticed as impurity, which may be due to entrapped unreacted chlorides of zirconium during precipitation process [28] The technique of AC impedance is well suited for the measurement of oxide ion conductivities of solid materials Two point probe AC measurements were carried out in frequency range of 20 Hz to MHz at an applied voltage of 1V Impedance graph involve plotting of the imaginary part (Z00 ) against the real part (Z0 ) Fig shows the complex impedance plots for two compositions C2 and C3 at temperatures 300 °C, 400 °C, and 500 °C Impedance spectra of the composites shows a single semicircle with vertical spike, indicating that the electrode are probably blocked and therefore electronic conduction is negligible or small compared to the magnitude of ionic conductivity Single semicircle at 38 N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 Fig SEM images of (a) ZrO2, (b) 8Mg, (c) 12Ca high frequencies region was attributed to the bulk properties of the material, whereas the inclined spike is the characteristic of the impedance of oxide ion conductor electrode electrolyte reaction It was observed from the plots that as the temperature increases the diameter of these semi circles become smaller and resistivity decreases, which ultimately increases ionic conductivity [29,30] It has to be noted that the complex impedance plot for composition C2 exhibit lower value of resistivity at constant temperature compared to composition C3 This is because resistivity decreases with increasing concentration of Mg and maximizes at lower concentration of Ca Fig represents the Arrhenius plots of oxygen ion conductivities for pure and doped samples Ionic conductivity of samples is expressed by an Arrhenius equation as rT ¼ r0 Â exp   ÀEa kT ð1Þ where rT is the total conductivity, the pre-exponential factor is r0, activation energy is denoted by Ea, and k is the Boltzmann constant [31] At lower temperature, pure ZrO2 was not a good oxide ion conductor; for conductivity enhancement anionic vacancies are promoted by doping [32] Above 190 °C, the drop in the conductivity was observed due to collapse of fluorite framework This supports the argument of lattice collapse, as reported earlier [33] Codoped sample shows a significantly higher conductivity and outperformed the single doped and undoped ones The conductivity obtained for C2 sample (6 Mg3Ca) is higher than C3 This is because grain boundary conductance increases as Mg content increases and maximizes at relatively lower concentration of CaO [34] From the graph, it has been observed that the conductivity of Mg doped Zirconia (C1) is higher than Ca-doped ZrO2 (C4), owing to small ionic size of Mg compared to Ca The high ionic radius of Ca results in blockage of oxide ions mobility, due to which conductivity decreases [35] A second rise in the conductivity above 450 °C indicate phase transition in ZrO2 because on dopping with aliovalent cation high temperature phase transition are maintain at lower temperature [24] Linear regression method was used to calculate activation energy at low and high temperatures as presented in Table The decrease in activation energy was observed from 0% to 6% increases in the content of MgO; owing to doping production of oxygen vacancies, which make ionic conduction easier Dielectric constant expressed the extent of distortion or polarization of electric charge distribution in the material as a function of frequency of applied electric field and is given as e¼ 11:3Ct A ð2Þ where capacitance in Farad is expressed by C, t is pellet’s thickness, and surface area of pellet is given by A Fig 7a shows a variation of dielectric constant with temperature at MHz for doped samples The highest dielectric constant was observed for the composition C2, which is slightly higher than composition C3 A significant increase in defect site and dipole take place with increase in concentration of dopant Dielectric constant first increases to 100 °C temperature and then decreases, above 150 °C it slightly increases till 300 °C and than rapidly increases with increase in temperature, due to increase in oxide ion mobility through solid electrolyte, this process was thermally activated The same pattern of plot was obtained for dielectric constant as observed for conductivity [36] Increase in temperature results in increasing value of dielectric constant, which attribute to the onset of dipole in the composite sys- N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 39 Fig Impedance spectra for the C0, C1, C2, C3, and C4 composite solid electrolytes tem that create a suitable path for migration of ions Additionally, it indicates the space charge polarization near interfaces of grain boundary [37], which results in large dielectric constant value of composite material at high temperatures [38] 40 N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 Fig Electrical conductivity as a function temperature for the C0, C1, C2, C3, C4 composite solid electrolyte Fig 7b Dielectric constant at different frequencies as a function temperature for the 6Mg3Ca composition Table The activation energies for various molar ratios of composite solid electrolytes at low and high temperature phase Sample C1 C2 C3 C4 Activation Energy (Ea) in eV 50–190 °C 450–700 °C 0.012 0.003 0.007 0.011 0.327 0.263 0.325 0.287 Fig Electrical modulus formalism at different frequencies as a function temperature for the 6Mg3Ca composition the reciprocal of dielectric constant and was used to investigate the space charge relaxation process The electrical modulus spectrum represents the measure of the distribution of ion energies and it also describes the electrical relaxation and microscopic properties The electrical modulus has been calculated using the following relation M¼ Fig 7a Temperature dependent dielectric constant at MHz for the C1, C2, C3, and C4 composite solid electrolyte The value of dielectric constant also varies when plot against different frequencies at constant temperature Fig 7b illustrates the plot of logarithmic e vs frequency for the composition 6Mg3Ca It shows the highest value for dielectric constant and conductivity when calculated in respect to temperature However, with respect to frequency, dielectric constant shows a decrease in values as the frequency increases, due to lower polarization In temperature range 300–550 °C, there is a sharp increase in the value of e, which might be due to space charge polarization in the materials [39] The electrical modulus formalism of solids having ion conductivity are widely analysed in term of electric modulus (M), and is e ð3Þ Fig shows the electrical modulus at different frequencies as a function of temperature As the temperature rises, the value of M decreases; however, the opposite trend was noticed in frequency At low frequency (due to single relaxation process), the value of M rapidly decreases and at high temperature it becomes slow Small contribution of electrode polarization brings M value closer to zero at low frequency and at high frequency, gradual increase in M value was observed due to saturation [40,41] Conclusions Zirconia based solid electrolyte with general formula {1 À (x + y)}ZrO2-(x)MgO-(y)CaO} have been synthesized with the N Zeeshan, Rafiuddin / Journal of Advanced Research (2018) 35–41 help of co-precipitation method Impedance graph consist of single semicircle with a spike Semicircle in high frequency region indicates the bulk resistance value and spike in lower frequency attributed to the oxide ion conductor electrode electrolyte reaction The co-doped composition ‘‘6Mg3Ca” have higher conductivity compared to ‘‘4Mg6Ca” In lower temperature region, C2 composition show minimum activation energy of 0.003 eV, which confirm that this composition has higher charge mobility within this range of temperature With increment of frequency, dielectric constant value decreased and with increasing temperature it shows the opposite trend On raising the temperature, the electric modulus of the sample decreases while frequency was increased Conflict of interest The authors have declared no conflict of interest Compliance with Ethics Requirements This article does not contain any studies with human or animal subjects Acknowledgements We express our gratitude to the Chairman, Department of Chemistry A.M.U Aligarh for providing the necessary facilities and UGC, New Delhi for financial support We are also thankful to STIC, Cochin University for XRD and TG/DTA analysis and USIF A.M.U, Aligarh for SEM analysis References [1] Raphael E, Jara DH, Schiavon MA Optimizing photovoltaic performance in CuInS2 and CdS quantum dot-sensitized solar cells by using an agar-based gel polymer electrolyte RSC Adv 2017;7:6492–500 [2] Liang F, Partovi K, Jiang H, Luoa H, Caro J B-site La-doped BaFe0.95xLaxZr0.05O3d perovskite-type membranes for oxygen separation J Mater Chem A 2013;1:746–51 [3] Ryu JH, Kil HS, Song JH, Lim DY, Cho SB Glycothermal synthesis of mol% yttria stabilized tetragonal ZrO2 nano powders at low temperature without mineralizers J Powder Technol 2012;221:228–35 [4] Zavodinsky VG The mechanism of ionic conductivity in stabilized cubic zirconia J Phys Solid State 2004;46:453–7 [5] Malavasi L, Craig AJ, Fisherb, Saiful Islam M Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features Chem Soc Rev 2010;39:4370–87 [6] Emam WI, Mabied AF, Hashem HM, Selim MM, Shabiny AME, Farag ISA Controlling polymorphic structures and investigating electric properties of Cadoped zirconia using solid state ceramic method Solid State Chem 2015;228:153–9 [7] Chen L, Liu Y, Li Y Preparation and characterization of ZrO2: Eu3+ J Alloys Compd 2004;381:266–71 [8] Mustafa E Microstructure and mechanical properties of PSZ toughened alumina ceramics prepared via polymeric sol–gel route PhD thesis from Faculty of Science, Cairo University [9] Hughan RR, Hannink RH Precipitation during controlled cooling of magnesia partially stabilized zirconia Am Ceram Soc 1986;69:556–63 [10] Manriquez ME, Picquart M, Bokhimi X, López T, Quintana P, Coronado JM Xray diffraction, and Raman scattering study of nanostructured ZrO2-TiO2 oxides prepared by sol-gel J Nano Sci Nanotechnol 2008;1:7–8 [11] Lee JS, Park J-II, Choi TW Synthesis and characterization of CaO-stabilized zirconia fine powders for oxygen ionic conductors J Mater Sci 1996;31:2833–8 [12] Dongare MK, Sinha APB Low temperature preparation of stabilized zirconia J Mater Sci 1984;19:49–56 41 [13] Ramaswamy, Agrawal DC Effect of sinterining zirconia with calcia in very low partial presuure of oxygen J Mater Sci 1987;22:1243–8 [14] Vijayakumar M, Selvasekarapandian S, Bhuvaneswari MS, Hirankumari G, Ramprasad G, Subramanian R, et al Synthesis and ion dynamics studies of nanocrystalline Mg stabilized zirconia Physica B 2003;334:390–7 [15] Iqbal MZ, Rafiuddin Structural, electrical conductivity and dielectric behavior of Na2SO4–LDT composite solid electrolyte J Adv Res 2015;7:135–41 [16] Wang JA, Valenzuela MA, Salmones J, Vazquez A, Garcıa AR, Bokhimi X Comparative study of nanocrystalline zirconia prepared by precipitation and sol–gel methods Catal Today 2001;21:30–68 [17] Ganapathi KR, Ashok CH, Rao KV, Shilpa CHC Structural properties of MgO nanoparticles: synthesized by co-precipitation technique Int J Sci Res 2013:43–6 [18] Perez-Maqueda LAP, Matijevic E Preparation and characterization of nanosized zirconium (hydrous) oxide particles J Mater Res 1997;12:3286–92 [19] Hao Y, Li J, Yang X, Wang X, Lu L Preparation of ZrO2-Al2O3 composite membranes by sol-gel process and their characterization Mater Sci Eng, A 2004;367:243–7 [20] Kumar R, Sharma A, Kishore N Preparation and characterization of Mg nanoparticles by co-precipitation method Int J Eng 2013;7:66–70 [21] Kumar R, Sharma A, Kishore N Synthesis and characterization studies of mgonio nanocomposites Intl J Engr Appl Magmt Sci Paradigms 2013;7:61–5 [22] Sanchez LML, Lee SW, Tohoru Sekino T, Gonzalez VR Practical microwaveinduced hydrothermal synthesis of rectangular-prism-like CaTiO3 Cryst Eng Comm 2013;15:2359–62 [23] Fan B, Zhang F, Li J, Chen H, Zhang R Synthesis and crystallization behavior of mol% yttria partically stabilized zirconia (3Y-PSZ) nanopowders by microwave pyrolysis process J Mater Sci Eng 2017;1:4–6 [24] Elashazly ES, Abdelal OAA Nickel stabilized zirconia for SOFCs: synthesis and characterization Intl J Metall Eng 2012;1:130–4 [25] Varshney P, Ahmad Sarita A, Beg S Study of phase transition in ZrO2 doped with Pb3O4 J Phys Chem Solids 2006;67:2305–9 [26] Zarkov A, Stanulis A, Sakaliuniene J, Butkute S, Abakeviciene B, Salkus T, et al On the synthesis of yttria-stabilized zirconia: a comparative study J Sol-Gel Sci Technol 2015;76:309–19 [27] Patil DS, Prabhakaran K, Dayal R, Prasad CD, Gokhale NM, Samui AB, et al Eight mole percent yttria stabilized zirconia powders by organic precursor route Ceram Int 2008;34:1195–9 [28] Ahmed TO, Akusu PO, Jonah SA, Rabiu N Phase evolution in co-precipitated stabilized zirconia powders Phys Rev Res Intl 2012;2:75–90 [29] Kumar PS, Balaya P, Goyal PS, Sunandan CS Effect of Cu-substitution on the conductivity of Ag-rich AgI–CuI solid solutions J Phys Chem Solids 2003;64:961–6 [30] Pradhan DK, Choudhary RNP, Samantaray BK Studies of structural, thermal and electrical behavior of polymer nanocomposite electrolytes eXPRESS Polym Lett 2008;2:630–8 [31] Iqbal MZ, Rafiuddin Synthesis, characterization electrical and dielectric studies of AgCuI and Co-SnO2 composite solid electrolytes Mater Res Bull 2016;73:296–301 [32] Rao CNR Phase transitions and the chemistry of solids Acc Chem Res 1984;17:83–9 [33] Murray RM, Secco EA Phase transformation studies on pure and K-doped Na2SO4 Can J Chem 1978;56:2616–9 [34] Singh OPM, Singh NK, Kumar D Preparation and characterization of ceria codoped with Ca and Mg Solid State Ion 2012;212:100–5 [35] Kharton VV, Naumovich EN, Vecher AA Research on the electrochemistry of oxygen ion conductors in the former Soviet Union I ZrO2-based ceramic materials Solid State Electrochem 1999;3:61–81 [36] Abbas HA, Hammad FF, Hanafi ZM, Anwar IE Electric and dielectric properties of scandia and ceria stabilized zirconia Can J Pure Appl Phys 2012;6:2161–7 [37] Maridurai T, Balaji D, Sagadevan S Synthesis and characterization of yttrium stabilized zirconia nanoparticles Mater Res 2016;19:812–6 [38] Pavic L, Milankovic AM, Rao PR, Santic A, Kumar VR, Veeraiah N Effect of alkali earth modifier ion on electrical, dielectric and spectroscopic properties of Fe2O3 doped Na2SO4-MO-P2O5 glass system J Alloys Compd 2014;604:352–62 [39] Li W, Ma Z, Gao L, Wang F Preparation and electrical properties of La0.9Sr0.1TiO3+d J Mater 2015;8:1176–86 [40] Badapanda T, Harichandan RK, Nayak SS, Mishra A, Anwar S Frequency and temperature dependence behaviour of impedance, modulus and conductivity of BaBi4Ti4O15 aurivillius ceramic process Appl Ceram 2014;8:145–53 [41] Onwudiwea DC, Arfin T, Strydom CA Synthesis, characterization, and dielectric properties of N-butylaniline capped CdS nanoparticles Electrochem Acta 2014;116:217–23  ... cation dopants (such as Y 3+, Ca 2+, Mg 2+, Ce 3+) was much higher than that of undersized trivalent cation (such as Al 3+, Fe 3+ and Cr 3+) dopants Thence, cations used as dopant for stabilization of... conducting oxide material are those based on ZrO2, CeO2 and ThO2 Recently, doped ZrO2 was the most studied solid ionic conductor, because of its attractive anionic conductivity, as well as good thermal... increase in M value was observed due to saturation [40,41] Conclusions Zirconia based solid electrolyte with general formula {1 À (x + y)}ZrO2 -(x) MgO-(y)CaO} have been synthesized with the N