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The present work investigates the role of oxygen partial pressure (PO 2) during the thin film growth in obtaining phase and controlling the crystallinity and optical responses in the thin films. Rietveld refinement of X-ray diffraction confirmed a rhombohedral structure of BNT as a major phase with secondary phase of Bi 2 Ti 2 O 7 and Bi 4 Ti 3 O 12. The diminutions of the secondary phase are observed with an increase in PO 2 , which signifies the crystal structure closely related to the partial oxygen pressure. The refractive index of films was found to be improved and optical bandgap energy was reduced with PO 2 due to the increase in crystallinity as well as decrease in oxygen vacancies. Nonlinear optical properties show a strong PO 2 dependency, self-focusing behaviour with a positive, large optical nonlinearity (n 2 = 4.62 × 10−6 cm2/W) and strong absorbance (β = 0.755 cm/W) for the film deposited at 10 Pa, which makes a potential candidate for the nonlinear photonic device applications. [ABSTRACT FROM AUTHOR]

A correlative study on optical and electrical properties of MgTiO 3 (MTO) -Ba 5 Nb 4 O 15 (BNO) composite thin films (MTBN) with respect to film thickness (260–450 nm) is reported. The optical bandgap energy of MTBN composite thin films (3.76 eV–3.65 eV) are found to be intermediate to MTO (3.44 eV) and BNO (3.85 eV) monoliths. Further, the optical dispersion in MTBN composite thin films can be defined by Cody-Lorentz dispersion law. Higher photoluminescence (PL) emission intensity and shorter carrier lifetime (0.8376 ns) ascribed to local symmetry break is observed for 450 nm film. Moreover, the Mott's variable range hopping mechanism was dominant conduction process in the MTBN composite films. Further, density of states near the Fermi level were found to be around 7.85 × 10 18 eV−1cm−3 - 3.478 × 10 19 eV−1cm−3 for 260 nm–450 nm MTBN films. The obtained optical and electrical properties prospect a potential application of the MTBN composite thin films in integrated microwave circuits. [Display omitted] [ABSTRACT FROM AUTHOR]

The 0.9 MgTiO 3 –0.1Ba 5 Nb 4 O 15 (0.9MTO-0.1BNO) thin films deposited on Pt (111)/TiO 2 /SiO 2 /Si (100) and SiO 2 substrates by RF reactive magnetron sputtering have been reported. The films are deposited at a substrate temperature of 400 °C under 50/50 argon (Ar 2)/oxygen (O 2) mixed ambiance by varying the film thickness. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) studies have confirmed presence of both MTO and BNO phases.. The obtained strain in the films is found to be reduced with an increase in film thickness. The 3d crystal structure of MTO exhibited significant variations in bond length for the films with different thicknesses. The dispersion in the refractive index of the films has obtained using the single electronic oscillator model, and the obtained bandgap value is found to be reduced from 3.75 to 3.34 eV with an increase in film thickness from 150 to 340 nm, accordingly. The films revealed uniform spherical shaped particles with smooth surface with small rms roughness values around 2.9 to 2 nm. The microwave and low frequency dielectric responses showed improvment with an increase in film thickness. The impedance spectroscopy analysis displayed Cole-Cole behavior indicating the non-Debye conduction process present in the films. The frequency dependent conduction process has analyzed by Jonscher's Power law and the non-overlapping small polaron hopping nature has been observed. Extracted activation energies estimated from conductivity are found to be in the range of 0.31 eV to 0.14 eV. The leakage current density (J) with the applied potential has found to be in the range of 10−6 A/cm2 at 100 kV/cm2 for 340 nm film. The obtained results suggest that these films are promising for optical and microwave integrated circuit applications. Unlabelled Image • MTO-BNO films were fabricated for microwave integrated circuit applications. • The fraction of O 2 in deposition chamber played crucial role in the growth of films. • Post annealing treatment is necessary for crystallization of the fabricated films. • Good quality films with minimal roughness are obtained by RF magnetron sputtering. • Obtained electrical responses are reasonably good for the intended application. [ABSTRACT FROM AUTHOR]

Oxygen vacancy engineering is one of the most effective strategies for tuning the microstructural properties of oxide nanomaterials. However, the connection between oxygen vacancies and electromagnetic (EM) wave absorption capacities is unclear. Herein, oxygen vacancy-boosted microwave absorption is realized over Gd-doped Ni 0.5 Co 0.5 Fe 2 O 4 (NCFO) nanoceramics. All magnetic properties are studied with the influence of induced lattice strain. Except for Ni 0.5 Co 0.5 Gd 0.075 Fe 1.925 O 4 (NCFOG3), which has an elevated saturation magnetization (M s) of 63 emu/g, the M s decreases with increasing Gd content. In addition, remnant magnetization (M r), coercivity (H c), and anisotropic constant (K) increased until Ni 0.5 Co 0.5 Gd 0.050 Fe 1.95 O 4 (NCFOG2) and then declined. The EM wave parameters: dielectric permittivity (ϵ'), magnetic permeability (μ'), dielectric loss (ϵ''), and magnetic loss (μ'') are systematically examined and found in the ranges of 2.07–3.5, 1.73–4.7, (4 × 10-2) – (2.2 × 10-1) and 0.18–0.35 respectively. Our finding shows that a small amount of Gd favors the high oxygen vacancy concentration, an appropriate lattice defect, and high magnetic and dielectric losses. The possible mechanism for EM wave absorption revealed the largely localized electrons and dipole centers created by the numerous oxygen vacancies causing the multiple reflection and scattering, which enhanced conductive loss, defect, and dipole polarizations. The maximum reflection loss (RL) -28.37 dB is observed at 17.80 GHz of a 2 mm thick sample for NCFOG3. This research reveals a distinct link between oxygen vacancy defects and EM wave dissipation capability, providing important information for developing better EM wave absorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon black (CB) reinforced lithium ferrite composites (LFO/CB) are synthesized to enhance EMI (electromagnetic interference) shielding effectiveness (SE) as nowadays EMI pollution is becoming a serious matter of concern for technology as well as human health. The formation of pure phase lithium ferrite and composites are analyzed. Though saturation magnetization decreased with the incorporation of CB, it did not create any huge decrement. Shielding efficiency is analyzed in the X band (8.2–12.4 GHz) and K u (12.4–18 GHz) band frequency range. The highest total SE (28 dB) is obtained for 20 wt% of CB with LFO (3 mm thickness), out of which reflection-based shielding effectiveness (SE R) is 4.58 dB and absorption based (SE A) is 23.17 dB. The highest absorption efficiency of the composites is measured to be ~99.68% for both LFO/CB (15) and LFO/CB (20) in the broad frequency range (8.2–18 GHz), which confirmed that the composite provides absorption-based SE rather than reflection based. Both real and imaginary part of permittivity drastically increased with incorporation of CB concentration (LFO: ε' = 4, ε"= 0.11; LFO/CB (20) : ε' = 46, ε"= 19.05 @8.2 GHz). Complex permeability also increased with CB content. However, dielectric, magnetic, and EMI shielding responses can be tailored by governing the amount of ferrite as well as carbon compound. Further, this study confirms that LFO/CB composites can be a potential candidate for application in the defense and telecommunication sector. • We synthesized ceramic based composites (lithium ferrite / carbon black) for high EMI shielding (28 dB) application. • It showed excellent efficiency in both X band (8.2 ‒ 12.4 GHz) and K u (12.4 ‒ 18 GHz) band. • It render high absorption efficiency (A eff = 99.68 %) rather than reflection. • High M s (57 emu/g), high dielectric and magnetic loss is observed for LFO/CB (20) (ε" = 19.05, µ" = 0.52 @ 8.2 GHz). [ABSTRACT FROM AUTHOR]

Sintering AlN composite ceramics at low temperatures without forming Al 2 O 3 poses is a significant challenge. This investigation demonstrates the comparative studies of conventional and microwave sintering of AlN ceramics with CaZrO 3 and Y 2 O 3 additives. In the conventional sintering method, the AlN composites are sintered at 1700 °C for 20 h in a powder bed. In contrast, the microwave sintering method, AlN composites are sintered at 1400 °C for 30 min in a susceptor bed. Both approaches successfully yield a pure wurtzite AlN structure with space group P 6 3 mc with no traces of secondary phase obtained for all pure and additive ceramics, achieving a relative density exceeding 97 % in the ACZ2Y sample. Raman spectroscopy further confirms the wurtzite structure AlN, characterized by six vibrational modes across all sintered composite ceramics. Dielectric properties are assessed over a temperature range of −140 to 200 °C and frequencies between 1 and 100 MHz. The optimal composite, ACZ2Y, displays microwave dielectric properties with ε r ∼9.94 and tan δ ∼11.04 × 10−4 sintered in the conventional sintering and ε r ∼9.02 and tan δ ∼7.34 × 10−4 in the microwave sintering, respectively. The microwave-sintered ACZ2Y composite also achieves the highest hardness of 1079.51 HV30, attributed to grain size and compactness. Compared to the conventional sintering method, microwave sintered composite exhibited superior dielectric properties, achieving appropriate relative density in short duration and at reduced sintering temperature. As a result, AlN ceramics produced by microwave sintering are excellent choices for electrical and microwave applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Aluminium nitride (AlN) requires a very high temperature >1900 °C in a specific environment (in the presence of nitrogen) to be densified. Many researchers have used different techniques for sintering: microwave sintering, spark plasma sintering, and conventional sintering. Microwave sintering is dangerous for operating, spark plasma sintering is expensive and conventional sintering is economical but time-consuming and difficult to obtain pure AlN phase. Preparing pure AlN ceramics is challenging because of the high sintering temperature. Since oxidation will occur at high temperatures while sintering, this study deals with the preparation of pure AlN ceramics and their dielectric and structural properties. In this study, AlN ceramics are prepared by conventional sintering at low-temperature 1700 °C for 30h by adopting the powder bed method in the presence of nitrogen. This powder bed consists of 70% AlN powder and 30% C (carbon) powder. These sintered AlN ceramics achieved maximum relative density ∼95% with wurtzite structure of space group P 6 3 mc, space group number 186, confirmed from XRD refinement. It is significant to note that the powder bed eliminated the formation of Al 2 O 3. The improvement in the density at the lower sintering temperatures is attributed to smaller initial particle sizes. The Raman spectra of AlN ceramics exhibits six phonon modes of wurtzite structure. The average grain size of sintered AlN ceramic is 1.45 μ m. The temperature-dependent Raman spectrum of AlN ceramics exhibits structure stability at various temperatures with stable wurtzite structure phonon modes. These sintered AlN ceramics exhibited good microwave dielectric properties as dielectric permittivity (ε r = 8.83) and dissipation factor (tanδ = 2.686 × 10−4). In this study, the AlN ceramic exhibits the best dielectric properties in the broad frequency range 1 MHz–100 MHz at a different temperature from −140 °C to 200 °C. The obtained properties of AlN ceramics are essential and appropriate for RF- window and electronic applications. [ABSTRACT FROM AUTHOR]

Material with low remnant polarizations with slim hysteresis loops are favorable for energy conversion efficiencies and have been receiving immense interest as energy storage materials with high recoverable energy densities. This study proposes a noble barium-based dielectric ceramic ((1- x)BaTiO 3 - x Bi[Zn 2/3 (Nb 0.85 Ta 0.15) 1/3 ]O 3) (BT-BZNT), with x ranging from 0.05 to 0.25 manufactured using solid-state reaction method. All the samples exhibited dual crystal symmetry revealing the coexistence of tetragonal (p4mm) and rhombohedral (R3c) phases with dense microstructures. The activation energy for conduction increased (0.37–0.61 eV) with BZNT substitution which might be attributed to a decrease in the density of states N(E F) from 3.91 × 1018 to 1.28 × 1018 eV−1 cm−3. This implies that oxygen vacancies and defects are reduced in samples with greater BZNT substitution, validating the elemental composition and oxidation states, which significantly enhance the energy storage capacity. At a lower applied field of 180 kV/cm, the BT-BZNT3 ceramic displayed a remarkably high recoverable energy density of 2.06 J/cm3 with an energy efficiency of 78 %. In the same applied field, an improvement in energy efficiency up to 96 % is achieved for higher BZNT substituted samples. These results have implications for the development of high-performance BT-BZNT ceramics for their use in future energy storage applications. [ABSTRACT FROM AUTHOR]

Sr-substituted polycrystalline lithium ferrites (Li 1- x Sr 2 x Fe 5- x O 8 (LSFO); x = 0, 0.003, 0.005, 0.007, 0.01) have been synthesized by solid-state reaction method. The effect of Sr substitution on structural, microstructural, dielectric and magnetic properties of LSFO ferrites are studied systematically. The Rietveld refinement of the XRD patterns revealed a single phase cubic structure for all the compositions and the lattice constants and unit cell volume are enhanced with Sr concentration. Further, Sr substitution led to a structral distortion and modified Fe - O bond length and Fe - O - Fe in both the tetradedral and octahedral positions. The surface morphology of LSFO ferrites displayed a dense microstructure and the average grain size is found to be reduced with Sr concentration, which showed that Sr inhibited the grain growth. The dielectric and magnetic properties of these samples are measured as a function of frequency (1MHz to 1GHz) and temperature (−140 °C to 250 °C). The sample with x = 0.003 exhibited the best dielectric response (ε r = 5986, tanδ = 1.17 @1MHZ, at RT). A shift in the critical temperature (160 oC– 200 °C) with diffuse transition has been observed which signifies a relaxor behavior, and analyzed by using Vogel– Fulcher and modified Curie Weiss laws. This behavior is complimented by the magnetic measurements also. The activation energies have been calculated by using the Arrhenius relation and found to be in the range of 0.142 eV - 0.07 eV. The variations in the permeability values are attributed to the magneto-crystaline anisotropy, thickness of domain walls and inner stress. The M-T measurements showed that the T c of the samples decreased with Sr content whereas magnetization value at RT enhanced significantly. However, the M-H curves shifted towards negative fields and displayed the soft ferrimagnetic response. The maximum saturation magnetization is found to be 61.5 emu/g for x = 0.007 sample. [ABSTRACT FROM AUTHOR]

A highly crystalline and pure phase Bi 0.993 La 0.007 FeO 3 (BLFO) thin films have been grown using a pulsed laser deposition technique. The structural analysis confirmed the thin film is well crystallized with a rhombohedral crystal structure with an R3c space group. The BLFO phase and composition are also confirmed by transmission electron microscopy and EDAX analysis. The surface chemistry of thin films, analysed by X-ray photon spectroscopy, reveals Fe's presence in Fe3+ and Fe2+ states. At RT, the deposited film exhibited high dielectric permittivity (∼4 × 102) and low dielectric loss (∼10−1). The isothermal magnetization on highly oriented (001)-MgO and LaAlO 3 (LAO) substrates is investigated. The response is compared to the randomly oriented polycrystalline films on low-cost substrates (Pt/TiO 2 /SiO 2 /Si and n-type Si substrate). The enhanced saturation magnetization of 57 emu/cm3 and 36 emu/cm3 at 10 K and 300 K are observed at 2.5 kOe applied field for the film grown on the LAO substrate. Additionally, the low leakage current density of the film is obtained around ∼1 × 10−7 A/cm2 at a field of 100 kV/cm. Acquiring single-phase BLFO thin films with enhanced electrical and magnetic properties can be relevant in designing multiferroic materials for multiple-state memories, magnetic field sensors, and spintronics applications. [Display omitted] • A highly crystalline and pure phase BLFO thin films have been grown using a pulsed laser deposition technique. • The deposited film exhibited high dielectric permittivity ∼4 × 102 and a low dielectric loss of ∼10−1 at room temperature. • The enhanced M s of 57 emu/cm3 and 36 emu/cm3 is observed at 10 K and 300 K respectively. • The leakage current density exhibited the space charge limited conduction mechanism in BLFO thin films. • The enhanced multiferroic properties are adequate for designing multiferroic materials for multiple-state memory. [ABSTRACT FROM AUTHOR]

The present study explores the structural, electrical and preliminary bioactivity of Ca 10 (PO 4) 6 (OH) 2 (HAP) – K 0.5 Na 0.5 NbO 3 (KNN) composites. The composites and monoliths of KNN and HAP are synthesized individually by the sol-gel and solid-state routes. The composites have been prepared by varying their At. % (20, 40, 60, and 80%). The purity of composite formation with the presence of both hexagonal and orthorhombic phases for HAP and KNN respectively without any reaction between monoliths was observed through the X-Ray diffraction (XRD) and Raman spectroscopy. The optical band-gap (E g) is studied using the UV/VIS/NIR spectroscopy that shows the major contribution of oxygen and OH vacancies towards the decrease of the bandgap. The morphology depicts the presence of both the nano-sized HAP and coarse KNN grains. The KNN grains are larger than HAP grains and a systematic variation is observed in composites with increasing At.% of KNN. The dielectric and impedance studies are carried out in the frequency range of 100 Hz–1 MHz. The dielectric constant (ε r) lies between 20 and 40 measured at 100 kHz. The ionic behavior of HAP contributed to the dielectric phenomenon, and an increase in ε r leads to conductivity. The impedance analysis draws a picture of the conduction phenomenon and the relaxation mechanism prevalent within the composites. The frequency-dependent ac conductivity (σ ac) curve follows Jonscher's universal power law. The comprehensive study of KNN – HAP bioceramic composites and understanding the electrical properties can open up possibilities for their applications in biomedical engineering. [ABSTRACT FROM AUTHOR]

Microwave ferrites are the most promising materials for high frequency and high-power devices. In this work, Co substituted Ni–Zn ferrites (Ni 0.5-x Zn 0.5 Co x Fe 2 O 4 ; x = 0–0.4) are synthesized, and the structural, morphology, dielectric, magnetic response are systematically investigated. The X-ray diffraction pattern (XRD) pattern confirmed the formation of pristine cubic phase alone without any secondary phase in all the samples. Substitution of Co2+ resulted in increased crystallite size and lattice constant. Raman peak intensity is suppressed, and a shift towards a lower wavenumber is observed with Co substitution. The change in position and intensity is analyzed and attributed to the change in cationic distribution in tetrahedral and octahedral positions by deconvoluting the Raman peaks. The Energy-dispersive X-ray spectroscopy (EDAX) analysis confirms the stoichiometry of compounds. The real permittivity and tan δ are decreased with the dilution of Co (x = 0: ε' = 24, tan δ = 0.015; x = 0.4: ε' = 11, tan δ = 0.035 @ 1 MHz). Further, permeability initially increased in the X band frequency range and decreased with increasing Co concentration. An increase in the saturation magnetization was observed initially with increased Co content and a decrease after x = 0.2. A maximum saturation magnetization (M s = 63.3 emu/g) observed for x = 0.2 composition. Interestingly, a giant coercivity and high effective magnetocrystalline anisotropy are observed with the incorporation of Co at low temperatures (5 K). The low dielectric loss, high saturation magnetization, and low coercivity at room temperature of Co substituted Ni–Zn ferrites suggest that these compounds are potential candidates for high-frequency devices (circulators). [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effects of high-energy ion irradiation on the structural, morphological, optical, and luminescent characteristics of ZnTiO 3 (ZTO) films. ZTO films were grown on silicon and quartz substrates via RF magnetron sputtering in pure argon ambiance and annealed at 800 °C for crystallization. The annealed (pristine) samples were irradiated with 50 MeV oxygen ions at three distinct fluences: 1 × 1012, 5 × 1012, and 1 × 1013 ions/cm2. X-ray diffraction (XRD) data demonstrates that the intensity of highly oriented (311) peak first increases with fluence up to 5 × 1012 and then decreases at 1 × 1013 ions/cm2. The root mean square roughness (RMS) increases initially from 8.22 (pristine) to 9.10 nm (1 × 1012 ions/cm2) and decreases to 8.25 nm for 1 × 1013 ions/cm2 fluence. Transmittance spectra indicate an enhancement in the transmission of irradiated films. The calculated band gap of pristine and irradiated films lies in the range of 3.93–3.84 eV. X-ray photoelectron spectroscopy (XPS) analysis reveals a reduction in oxygen vacancies up to a fluence of 5 × 1012 and then rises at 1 × 1013 ions/cm2. The enhancement of peak intensity is observed in photoluminescence (PL) spectra on increasing the ion fluence due to a reduction in the non-radiative recombination centers. • ZnTiO 3 films grown using RF sputtering were irradiated with 50 MeV oxygen ions. • XRD results indicate variation in crystallinity with ion fluence. • A reduction in band gap was observed for irradiated films. • PL peak intensity increases for irradiated samples compared to pristine films. [ABSTRACT FROM AUTHOR]

MgTiO3 (MTO) ceramics have been prepared by the conventional solid-state reaction method. The effects of CeO2 nanoparticles up to 1.5wt% as a sintering aid and annealing temperature on the crystal structure, microstructure and microwave dielectric properties of MTO ceramics were investigated. It is found that the addition of CeO2 nanoparticles to the MTO ceramics leads to improvement in the relative density, reduction in sintering temperature. However, Q×f o values are found to decrease marginally. The driving forces for the improved sintering process are the large surface energy of CeO2 nanoparticles and their defect energy, which are activated during the sintering process. The addition of CeO2 nanoparticles does not change the dielectric constant (ε r ), and the unloaded quality factor (Q u ) but the τ f values are altered significantly. The annealing temperatures of the pure MTO ceramics and MTO+xCeO2 (x=0.5, 1.0 and 1.5wt%) were optimized. The samples annealed at 1100°C for 48h exhibit the best microwave dielectric properties. The maximum value of Q×f o for the pure MTO was achieved by sintering at1400°C and significantly such maximum value was achieved in x=0.5wt% sample by sintering at 1300°C itself. The values of Q×f o are in the range of 52250–140800GHz. Pure MTO ceramics sintered at 1400°C and annealed at 1100°C for 48h exhibit the best microwave dielectric properties (ε r =17.21, Q׃ o =165500GHz). The observed results are correlated to the reduction in oxygen vacancies, relaxation of strain during annealing, increase in grain size and relative densities. [ABSTRACT FROM AUTHOR]