Secondary Crystalline Phases Research Articles

Structural, morphological and Magnetic studies of Soft magnetic Fe-Si-B Metallic Glass ribbons

Abstract A comparative study of two metallic glass ribbons produced by two different industries namely M/s Honeywell corporation, U.S.A., and M/s Vijay electricals. The potential of different experimental techniques like XRD, SEM and EDAX and VSM has been carried out for two soft metallic glass ribbons. XRD studies reveal that for sample A has two broad peaks and sample B shows the absence of any sharp peaks indicating crystalline secondary phases are <5%. Morphological studies show that sample A has homogeneous matrix whereas sample B has crystallites of varied shapes and sizes distributed in the range of 5-40 μm. EDAX for both the samples A and B was done to investigate the compositional elements. VSM measurements reveals sample B to exhibit a relatively larger anisotropy compared to sample A.

Selective conversion of spent cracking catalyst to faujasite-structured zeolites

Current recycling strategies for spent catalyst in Fluid Catalytic Cracking (FCC) focus on valuable rare-earth elements (REE) and sometimes include a reuse of spent materials by down-cycling, which hinders a circular economy. Herein, a new procedure for the selective conversion of spent FCC catalysts to FAU-type zeolite without secondary crystalline phases such as sodalite, zeolite P or zeolite A is reported. The steps include a leaching process of REE, followed by thermal activation with sodium hydroxide and acid treatment to get an aluminum-rich feed. The synthesis of FAU-type zeolites with varying Si/Al ratios uses the aluminum-rich catalyst feed and commercial water glass. The experiments show that incorporation of silicate from water glass into the zeolite structure is limited to zeolite products with Si/Al ratio ≤ 2.0. It indicates a flocculation of silicates in higher concentration in competition to the crystallization process of FAU-type zeolites. This is reinforced by the resulting crystals, covered and surrounded with small particles with morphology of silica. Moreover, a clear differentiation between zeolite Y and zeolite X is possible from materials properties with the definite evidence of a mixed phase. The kinetics of feed dissolution and incorporation of impurities, alumina and silica are controlled by the pre-treatment temperature, duration and silicon source. This enables flexible adjustment of the aluminum re-use from spent FCC catalyst, the amount of foreign elements (Fe, Ni, V), phase purity, Si/Al ratio, specific surface area and thermal stability of the final zeolite product. Structural and textural data of the resulting zeolites reveals high crystallinity > 80 %, Si/Al ratios of 1.6–2.0, and specific surface areas up to 780 m2/g.

Fe-rich X-ray amorphous material records past climate and persistence of water on Mars

X-ray amorphous material comprises 15-73 wt.% of sedimentary rocks and eolian sediments in Gale crater. This material is variably siliceous and iron rich but aluminum poor. The presence of volatiles is consistent with the existence of incipient weathering products. To better understand the implications of this material for past aqueous conditions on Mars, here we investigate X-ray amorphous material formation and longevity within terrestrial iron rich soils with varying ages and environmental conditions using bulk and selective dissolution methods, X-ray diffraction, and transmission electron microscopy. Results indicate that in situ aqueous alteration is required to concentrate iron into clay-size fraction material. Cooler climates promote the formation and persistence of X-ray amorphous material whereas warmer climates promote the formation of crystalline secondary phases. Iron rich X-ray amorphous material formation and persistence on Mars are therefore consistent with past cool and relatively wet environments followed by long-term cold and dry conditions.

Structural features and thermal expansion of zinc aluminosilicate quartz solid solutions

Zinc aluminosilicate (ZAS) glasses were synthesized along the peraluminous join (SiO2 contents between 95 and 50 mol%) by melt-quenching or sol-gel spray-drying and subjected to controlled heat treatments to obtain ZAS quartz solid solutions (Zn-Qz-ss). The precipitation of Zn-Qz-ss is non-stoichiometric with respect to their parent glass and the crystals undergo a compositional evolution during annealing, even in absence of secondary crystalline phases. Near-hexagonal high-quartz-like crystals with negative thermal expansion (down to −3 × 10−6 K−1) can be obtained in the range 50–80 mol% SiO2, while SiO2-richer crystals exhibit positive thermal expansion at room temperature (up to 29 × 10−6 K−1). Zn2+ ions occupy two distinct positions within the structural channels of quartz, with a strong preference for 4-fold coordination. In analogy to lithium aluminosilicate quartz solid solutions (Li-Qz-ss), the low-to-high phase transition exhibits a linear correlation to the composition of the crystals.

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44−, Ca2+, PO43−, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. Statement of significanceA novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Manufacturing process and annealing influence on the dynamic mechanical properties and physical structure of LLDPE thin films

Thin films of Linear Low-Density Polyethylene are used for stratospheric balloon applications. They undergo tensile mechanical stress on a wide range of temperatures [-95; 55]°C. The aim of this study is to compare the influence of blown film and double-bubble manufacturing processes on the crystalline phase and mechanical properties of the films through their operating temperatures (flight, storage, and transportation temperatures). Dynamic Mechanical Analysis and Differential Scanning Calorimetry have been used to monitor the dynamic mechanical properties in tension mode and the crystalline phase of the films respectively. The films mechanical properties are dependent on their manufacturing process. The double-bubble process allows isotropic tensile mechanical properties regarding stretching direction, whereas the blown film process favors only transversal direction. To simulate different storage conditions, annealing has been performed. The influence of annealing on the tensile mechanical properties of the films depends mainly on the internal stress stored during manufacturing. The double-bubble process produces a biaxially stretched film with a higher stretching ratio than blown films. The dissipated internal stress can be associated with thermal shrinkage and goes up to 10 % for the biaxially stretched film. The more internal stress is stored, the more E′ and E″ increases. Annealing also favors the formation of a secondary crystalline phase that is dependent on annealing temperature and time, and exhibits αc relaxation. After annealing, the amorphous phase is less stretched, and the crystalline phase keeps its orientation.

Study on magnesia alumina spinel heat storage ceramics for solar thermal power generation

AbstractSolar thermal storage ceramic materials use photothermal power generation technology to store heat energy, which is an important way to use clean energy and reduce carbon emissions. In this paper, MgAl2O4 ceramics were prepared by pressureless sintering with fused magnesia and α‐Al2O3 as the primary raw materials and TiO2 as the additive. The phase composition, microstructure, physical properties, thermal shock resistance, and thermal physical properties of MgAl2O4 thermal storage ceramics were studied. The results show that the main crystalline phase of B4 is MgAl2O4 and the secondary crystalline phase is MgTi2O5. Ti4+ is dissolved into MgAl2O4 lattice, which distorts the lattice, reduces activation energy, and promotes sintering. The sample B4 (69.73 wt% α‐Al2O3, 30.27 wt% fused magnesia, and 7 wt% TiO2) sintered at 1510°C had the best comprehensive physical properties, and its bending strength and bulk density were 89.41 MPa and 3.27 g/cm3, respectively. After 30 thermal shock cycles, the bending strength of the sample B4 is slightly lost. The thermal stress generated during the expansion and contraction of the grain volume led to the decrease of the bending strength. From room temperature to 1000°C, the specific heat capacity of sample B4 is .44–1.25 J/(g·K). The heat capacity increases with the increase of temperature, and the heat storage density increases. The heat storage density is 1218.75 kJ/kg (1000°C). Heat capacity increases with temperature due to intensified lattice vibration at high temperatures. Therefore, magnesia alumina spinel ceramics show great potential in solar thermal energy storage.

Pu(VI) Oxalate Crystal Structure and Evidence of Photoreduction to Pu(IV) Oxalate.

We report the first crystal structure of a Pu(VI)-oxalate compound. This compound, [PuO2(C2O4)(H2O)]·2(H2O) (1), crystallizes in space group P21/c with a = 5.5993(3) Å, b = 16.8797(12) Å, c = 9.3886(6) Å, and β = 98.713(6)°. It is isostructural with the previously reported U(VI) compound, [UO2(C2O4)(H2O)]·2(H2O). Each plutonyl ion (PuO22+) is coordinated in the equatorial plane by two side-on bidentate oxalates, creating an infinite chain along [001]. A coordinated water molecule and twisting of the oxalates lead to a distorted pentagonal bipyramidal geometry of the Pu. A photochemical degradation was observed for 1, which resulted in the formation of a secondary crystalline phase. The absorption spectrum of this secondary phase confirmed the presence of Pu(IV), but it did not match the spectrum of Pu(C2O4)2·6H2O, which is considered to be the primary product of Pu-oxalate precipitation. While compound 1 has previously been proposed to exist in solution, this is the first time it has been isolated via crystallization. Although redox interactions between Pu and oxalate have been documented in the literature, the present study is the first observation of a photochemical reduction of Pu(VI)-oxalate. As a result, this study has expanded on the limited understanding of the Pu(VI)-oxalate system, which is important for nuclear fuel cycle applications.

Formation and detection of secondary crystalline phases in Cu2SnS3 thin films for photovoltaic applications

Formation and detection of secondary crystalline phases in Cu2SnS3 thin films for photovoltaic applications

Alkali Activation of Clay and Water Potabilization Sludge Binary Blends: Influence of Composition and Curing Conditions

This work aims to evaluate the compatibility and features of alkali-activated blends obtained by replacing carbonate-rich illitic clay with either untreated or heat-treated water potabilization sludge (WPS). The experimental setting was created looking towards producing environmentally friendly solutions such as precursors that are sourced from the same territory, room-temperature curing in realistic environmental conditions, and activation exclusively with sodium hydroxide (NaOH) solutions. A multi-analytical characterization of the blends using X-ray powder diffraction (XRPD), an optical microscope (OM), a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDX), and a mechanical test demonstrated that up 75% of calcinated sludge and 25% of uncalcinated sludge could be successfully incorporated into the clay-based blends, offering a valuable alternative to landfill disposal of WPS. The matrices’ features were affected both by the amount of sludge in the blends and by the environmental conditions curing. since mineralogical investigations, OM and SEM observations showed the formation of secondary crystalline phases, mainly zeolitesin addition to amorphous gel. The mechanical strength results reached values between ~3 and 9 MPa, suggesting the possible use of the investigated alkali-activated blends for the formulation of precast building materials. Furthermore, to assure the replication of these alkali-activated blends, uncontrolled (T °C and RH%) curing does not appear to be the most appropriate solution. The study demonstrated that WPS, traditionally destined for landfill, could be a resource for the production of alkaline-activated materials by partially replacing unrenewable raw materials. thus resulting in the creation of eco-sustainable and economic processes as WPSare a widely and locally available industrial byproduct. However, a better control of mix designs and curing conditions is necessary for the upscaling of the here investigated blends.

Low temperature densification and dielectric characterization of CeO2 ceramics

A near full densification is essential to obtain high dielectric constant and quality factor together with minimum dielectric loss for microwave dielectrics. Limited densification of CeO2 ceramics was improved by using 5 wt% anorthite-based glass and a high densification between 1050 °C and 1150 °C range (e.g., relative density 97.5–99%) was successfully obtained. Phase analysis revealed a cubic CeO2 phase without any crystalline secondary phases formed. Dielectric properties followed the densification path such that maximum dielectric constant (minimum dielectric loss) was obtained at 1150 °C as 21.36 (0.0040) at 5 MHz. The unloaded quality factor (Q), resonance-frequency dependent quality factor (Qxf), and dielectric constant (loss) for a TEM mode dielectric resonator were calculated as 445, 1288 GHz, and 21 (0.0022), respectively. The CeO2-(anorthite-based) glass ceramic was studied for the first time in literature and the results are promising from the low temperature densification and microwave properties points of views.

Effects of Nonmagnetic Zn2+ Ion and RE Ion Substitution on the Magnetic Properties of Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE = La, Sm, Gd) by Sol-Gel.

Magnetic Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE (rare-earth) = La,Sm,Gd) were prepared using the sol-gel combustion method. XRD characterization confirms that the ferrite samples we synthesized are single-phase cubic structures. The variation in the average crystalline size and lattice parameter is related to RE ion doping. The Mössbauer spectra of CoRExFe2-xO4 are two sets of magnetic six-wire peaks that indicate the ferrimagnetic behavior of the sample. The calcination temperature greatly influences the absorption area of Mössbauer for CoFe2O4, indicating that the calcination temperature affects the iron ion content at the octahedral B and tetrahedral A sites. Additionally, scanning electron microscopy measurements of the substituted specimens reveal that the ferrite powders are nanoparticles. With an increase in RE ions, the coercivity increases, and the saturation magnetization changes obviously. The XRD characterization of Co0.7Zn0.3LaxFe2-xO4 shows that the main crystalline phase of the sample is the cubic spinel structure phase, and there are fewer secondary crystalline phases. The lattice parameter tends to decrease with the substitution of La3+ ions. The average grain size decreased significantly with the increase in La content. From ferrimagnetic state transition to relaxation behavior, the hyperfine magnetic field decreases in La concentration by room temperature Mössbauer spectra. With the substitution of La3+ ions, both the saturation magnetization and coercivity of the samples were reduced, and the coercivity of all samples was lower.

Structural, optical and magnetic properties of ErxZn1-xO nanoparticles: The impact of the Er-content

In this study we report on both the successful synthesis of ErxZn1-xO nanoparticles (x = 0.000, 0.005, 0.010, 0.030, 0.050, 0.075, and 0.100) and characterization (structural, optical, and magnetic) of the as-produced nanomaterials. The nanoparticles were produced by the polymeric precursor method (Pechini’s method). X-ray diffraction and Raman spectroscopy showed formation of hexagonal wurtzite phase in all samples. Meanwhile, only samples with a high Er-content (x = 0.075 and x = 0.100) exhibited a minority (up to 7 % w/w) secondary crystalline phase (Er2O3). The Rietveld refinement method was employed to assess details of the structural parameters. It was demonstrated that the increase of the Er-content leads to systematic mean crystalline size reduction (from ∼80 to ∼13 nm) and band gap shrinking (from ∼3.17 to ∼3.00 eV). The UV-Vis spectra showed the presence of characteristic Er3+-ion absorption bands. Likewise, emission peaks associated with Er3+-ion 4S3/2 → 4I15/2 electronic transition were verified by room temperature photoluminescence (PL). Strong differences in the PL spectra profiles of the ErxZn1-xO nanoparticles with respect to the PL spectrum of a reference Er2O3 sample, suggested that the majority of Er3+-ions replace Zn2+-ions in the wurtzite hosting matrix. Magnetic measurements show a paramagnetic behavior in all doped samples. The χ×T and M×Hcurves were successfully fitted to Curie-Weiss law and Brillouin modified model, showing the existence of short-range antiferromagnetic correlation.

Enhanced flux pinning by refined structural/magnetic domains in nickel-doped BaFe2As2 single crystals

The critical current density at high magnetic fields of high-temperature superconducting single crystals and films is mainly determined by the flux pinning force arising from interactions between fluxons and crystalline defects or secondary phases. However, iron-based superconductors, which are acknowledged as promising candidates for high-field applications, suffer from a lack of strong flux pinning centers. It leads to a critical current density (Jc) inferior to that of iron-based superconducting films. In this work, we applied a simple annealing method to tailor flux pinning structures in slightly underdoped BaFe2-xNixAs2 single crystals without significantly compromising superconductivity. We propose that the probable strengthened orthorhombic distortion by post-annealing could generate twin domain boundaries or short-range antiferromagnetic clusters with sizes comparable to the in-plane coherence length. The inclusion of the structural/magnetic structures enhances electron scattering but also provides potent flux pinning centers. Ultimately, the Jc is enhanced by 2.5 times in the samples with optimized pinning landscapes. Our studies highlight the importance of further exploring underdoped iron-based superconductors, in which magnetic/orthorhombic phases that compete and coexist with superconductivity may also act as effective pinning centers.

Preparation and curing method of red mud-calcium carbide slag synergistically activated fly ash-ground granulated blast furnace slag based eco-friendly geopolymer

The commercial alkali activators could account for more than 50% of the cost for producing geopolymers. Thus, to lower the carbon footprint of geopolymer by avoiding the utilization of energy-intensive commercial alkali activators, a novel eco-friendly geopolymer was synthesized from 100% solid wastes comprising red mud (RM), calcium carbide slag (CS), ground granulated blast furnace slag (GGBS) and fly ash (FA) in this study. Effects of GGBS contents and curing conditions on the compressive strength, fluidity and water requirement for normal consistency were investigated. The hydration products in the binders cured at different conditions were characterized by X-ray diffraction (XRD), thermogravimetric (TG), Fourier transformation infrared spectroscopy (FTIR) and scanning electronic microscopy (SEM). The results showed that GGBS improves the compressive strength as well as the mortar fluidity and reduces the water requirement for normal consistency of the geopolymer. Raising the curing temperature up to 60 °C and prolonging the heat curing duration to 12 h facilitate the dissolution and polymerisation of the FA-GGBS and therefore increase the amount of gel and crystalline products, whereas excessive heat-curing at temperatures higher than 60 °C and durations longer than 12 h causes shrinkage cracks at later age, which was detrimental to the compressive strength. The mineralogical characterization revealed that the amount of gel governs the strength development and heat curing favors the formation of secondary crystalline phase hydrotalcite. The developed binder can be used to produce low-carbon clinker-free concrete blocks to improve the sustainability of concrete industry.

Dual roles of Cr2O3 in preparation of glass-ceramics from ferronickel slag

The dual effects of Cr2O3 in the fabrication of glass-ceramics from ferronickel slag (FNS) with the addition of coal fly ash (CFA) were investigated by varying the content of Cr2O3 from 0 wt % to 2.0 wt %. The crystallization kinetics results showed that as the Cr2O3 content increased from 0 wt % to 1.6 wt %, the crystallization activation energy of the parent glass decreased from 448.23 kJ/mol to 232.65 kJ/mol with the change of crystallization mode from surface crystallization to bulk crystallization. When the content of Cr2O3 reached 1.6 wt %, there existed the highest degree of depolymerization of the glass network and the strongest crystallization tendency. The prepared glass-ceramic was composed of enstatite as the main crystalline phase and spinel as the secondary crystalline phase. The microstructure changed from a loose tabular structure to a dense spherical structure. As the Cr2O3 content further increased to 2.0 wt %, the crystallization activation energy increased to 304.21 kJ/mol and the spherical structure became inhomogeneous due to the coexistence of enstatite particles with different sizes. By controlling the Cr2O3 content of 1.6 wt %, an optimal glass-ceramic with density of 3.17 g/cm3, bending strength of 175 MPa, Vickers microhardness of 9.51 GPa, acid resistance of 99.99% and alkali resistance of 99.97% was obtained. This study provided a novel method for promoting conversion of FNS to glass-ceramics.

Syntheses and characterization of Twofold Nepheline-Combeite Glass-Ceramics for Dental Application

Synthesis of glass-ceramics with a combination of specific crystalline phases can lead in materials with superior chemical, physical and mechanical properties. The aim of this study is to outline the potential of synthesizing a novel glass system which crystallise into two crystalline phase's nepheline-combeite and provide an end monolithic glass-ceramics via sinter crystallization route for dental applications. Four novel glass compositions based on the Na2O-CaO-Al2O3-SiO2 system were synthesized using the melt-quench method. Glasses were designed to contain 6 mole % of CaO and a total of 35 mole % of Al2O3 and Na2O. Experimental glasses were ground into fine powders and then sinter crystallized to monolithic glass-ceramics. The developed glasses and glass-ceramics were characterized using DSC, Dilatometry, X-ray diffraction, Nuclear Magnetic Resonance (MAS-NMR) and scanning electron microscopy. This study shows how the nepheline phase can be produced in combination with other secondary crystalline phases which allow tailoring of the chemical, physical and thermal properties of both the starting glasses and the end glass-ceramics, including their thermal expansions coefficients, glass transition temperatures, softening points, sintering and melting temperatures.

A mineralogical study of glacial flour from Three Sisters, Oregon: An analog for a cold and icy early Mars

Geomorphic and mineralogical data from the martian surface indicate liquid water was abundant on the martian surface and near subsurface ∼3.5 to 4 Gyr ago, but whether early Mars had a warm and wet climate or whether it was cold and icy with punctuated periods of warmth is still unknown. Mineral assemblages of sedimentary rocks on Mars help determine past aqueous conditions and sediment sources. Here, we report on the primary and secondary mineral and amorphous assemblage of glacial flour from Collier Glacier valley on the northern flank of North Sister in Oregon, U.S.A. to identify mineralogical characteristics of mafic sediments altered under cold, wet conditions. Collier glacial flour is dominated by primary igneous minerals (plagioclase is dominant, with lesser amounts of pyroxene and olivine) and comprises 10-40 wt.% X-ray amorphous materials. Crystalline secondary phases (e.g., phyllosilicates, zeolite) are not significant contributors to the authigenic alteration assemblage. High-resolution transmission electron microscopic observations of the <2 μm size fraction of the flour demonstrate that the X-ray amorphous materials are both primary (i.e., volcanic glass) and secondary in nature. The secondary X-ray amorphous materials are enriched in Si, Al, and Fe, and we observe incipient phyllosilicate formation associated with primary and secondary amorphous materials. Our results indicate chemical weathering on a cold and icy early Mars would have produced X-ray amorphous materials, but not crystalline secondary phases. We suggest that the abundant X-ray amorphous materials recognized from orbit and in situ on Mars could have formed under cold and periodically wet conditions similar to those on North Sister today. Furthermore, the lack of volumetrically significant phyllosilicate formation in Collier Glacier flour indicates phyllosilicates on Mars did not form in a cold and wet climate.

Microstructure, hardness, and fracture toughness evolution of hot-pressed SiC/Si3N4nano/micro composite after high-temperature treatment

AbstractThe grain boundary phases in SiC/Si3N4nano/micro-composite changes with time of high temperature treatment at 1750 °C in nitrogen atmosphere. Stable phases were obtained after 26 hours of annealing. Moreover, the average grain diameter distribution was significantly changed. The hardness and fracture toughness of the SiC/Si3N4nano/micro-composites decreased with the duration of the high-temperature treatment. Both findings can be explained by the different secondary crystalline phases formed during the high-temperature treatment. Phases Si2N2O, Y2SiO5, and Y2Si2O7, typical for the samples treated up to 4 h, were replaced by the YNSiO2phase in the samples treated longer than 26 h. Anisotropy of the measured mechanical properties in different sample cross-sections caused by the Si3N4grain alignment become negligible after long term high-temperature treatment.

Effects of Ta2O5 on the microstructure and electrical properties of ZnO linear resistance ceramics

ZnO linear resistance ceramics were synthesized from ZnO–Al2O3–MgO–TiO2–SiO2–Ta2O5 by a conventional ceramics method. Effects of Ta2O5 on the phase composition, microstructures, and electrical properties of ZnO linear resistive ceramics were investigated. The results show that doping with appropriate amount of Ta2O5 can refine the grains of the main crystalline phase ZnO and the secondary crystalline phase ZnAl2O4 in terms of microstructure, and also can reduce the grain boundary barrier and optimize the I–V characteristics in terms of electrical properties. In addition, the doping of Ta2O5 can improve the stability of the resistivity , and the impedance frequency indicates that the doping of Ta2O5 makes the sample suitable for high-frequency electric fields. The resistivity of the sample doped with 0.2 mol% Ta2O5 is 56.2 Ω·cm, and this sample has the best grain boundary barrier height, nonlinear coefficient and temperature coefficient of resistance of 0.054 eV, 1.04 and −3.48 × 10−3 °C−1, respectively.