Silver Point Research Articles

Preparation of high-performance Bi-YG ferrite based on LTCC technology and theoretical analysis of its sintering mechanism

In the preparation process of Microwave Multi-Chip Module (MMCM), it is necessary to simultaneously sinter both microwave medium (ferrite) and silver electrodes. Hence, this necessitates keeping the sintering temperature below the melting point of silver (961 °C). An excessively low sintering temperature would significantly impair the electromagnetic properties of the ferrite material. To address this concern, this study synthesizes Bi-YIG (Y3-xBixFe5O12, x = 0–1.0) ferrites with optimized characteristics, including low ferromagnetic resonance line-width (ΔH) and high saturation magnetization (Ms), at 945 °C using Low Temperature Co-fired Ceramic (LTCC) technology. The mechanism of low-temperature liquid phase sintering, facilitated by a fluxing agent, was investigated using a theoretical model. The addition of Bi2O3 fluxing agent was found to reduce the reaction activation energy, disrupt the chemical reaction equilibrium, and promote low-temperature liquid phase sintering, thus lowering the critical sintering temperature below the melting point of silver. Furthermore, optimal bismuth content was identified to regulate the dynamic balance between grain growth and boundary diffusion, suppressing abnormal grain growth and enhancing the electromagnetic properties of the ferrite. This exploration, leveraging LTCC technology, may offer valuable insights for enhancing the overall performance of MMCMs.

Silver catalytic effect on flash sintering of ceramics

We investigated the use of metallic silver as a catalyst for flash sintering on hydroxyapatite/zirconia (HZ) composites. Adding 3 wt% of silver to the ceramic powder reduced the flash onset temperature (from 1084 °C to 925 °C) and also the electric field (from 300 V cm−1 to 150 V cm−1) used in the process. We attribute this behaviour to the formation of a silver percolation path that acts as a heat source, accelerating the thermal runaway. As a result, both the flash temperature and the required electric field were reduced. Furthermore, the results suggest that the temperatures along the percolation paths are high enough to reach the boiling point of silver, forming a gaseous phase that leaves the sample.

Final report for CCT comparison of ITS-90 realisations above the silver point using two transfer radiation thermometers and a set of high temperature fixed-point blackbody cells

Main textThis report outlines the equipment, measurement method, results and uncertainties associated with the participant measurements for the Consultative Committee of Thermometry Key Comparison K10 (CCT-K10), "ITS-90 realisations above the silver point using two transfer radiation thermometers and a set of high temperature fixed-point blackbody cells", over the period from around summer 2014 to the final measurements made during January 2020. The report presents differences of the participant data from the KCRV values for both the radiation thermometer and HTFP measurements. Note: this interim report excludes the measurement data of VNIIM, Russia - see explanation at the end of Section 6.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Comparison of local realizations of Silver freezing-point temperatures between NMIA and NMIJ AIST

Main textThe key comparison CCT-K4.1 was initiated on the request of the National Measurement Institute, Australia (MNIA) to re-link their standards to the Consultative Committee for Thermometry (CCT) Key Comparison (KC) and facilitate the NMIA CMC submission. National Metrology Institute of Japan, Japan (NMIJ) provided the linkage to the CCT-K4 at the temperature of the freezing point of silver. At the time of the CCT-K4 NMIA (formerly CSIRO-NML) had only one silver cell and this was found to be contaminated shortly after completion. Subsequently, more silver cells were fabricated at different times to form an ensemble of five cells before the start of CCT.K4.1.In the CCT-K4.1 bi-lateral comparison, a silver cell provided by NMIA and used as the artefact and circulated in accordance with the pilot-participant-pilot scheme. It is standard practice for NMIJ to use argon at 6N purity and NMIA argon 5N purity to regulate the pressure in the silver cell. To mitigate this, the effect of different argon purity was assessed in the post-circulation measurements. First the comparison was made under 6N purity atmosphere to preserve the cell ambience after it left NMIJ then the measurement was repeated under 5N argon atmosphere.The linkage was based on the temperature of NMIJ reference Ag fixed point relative to the key comparison reference value (KCRV) of CCT-K4 at the Ag fixed point via the difference in temperature between the NMIA reference Ag fixed point and NMIJ reference Ag fixed point (links to the KCRV of the CCT-K4). The temperature difference between the standards of NMIA and the KCRV of the CCT-K4 was within the evaluated comparison uncertainties of the CCT-K4.1. This report provides detailed information on the comparison results, linkage mechanism, and the Degree of Equivalence of NMIA relative to the institutes having participated in the CCT-K4.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Comparison report of the ITS-90 realization at the freezing point of silver between NIM and CMS

Main textThe APMP key comparison APMP.T-K4.1 was initiated on the request of the Center for Measurement Standards, Taiwan (CMS) to link their standards to the Consultative Committee for Thermometry (CCT) Key Comparison (KC) and facilitate the CMS CMC submission. National Institute of Metrology, China (NIM) provided the linkage to the CCT-K4 at the temperature of the freezing point of silver. In the APMP.T-K4.1, one high temperature standard platinum resistance thermometer (HTSPRT) was chosen as the transfer instrument and was calibrated at the freezing point of silver. The comparison was carried out in a participant-pilot-participant sequence where NIM served as the pilot. The linkage was based on the temperature of CMS reference Ag fixed point relative to the key comparison reference value (KCRV) of CCT-K4 at the Ag fixed point via the difference in temperature between the NIM reference Ag fixed point and NIM reference Ag fixed point (links to the KCRV of the CCT-K4). The temperature difference between the standards of CMS and the KCRV of the CCT-K4 was within the evaluated comparison uncertainties of the ATPM.T-K4.1. This report provides detailed information on the comparison results, linkage mechanism, and the Degree of Equivalence of the CMS relative to the institutes having participated in the CCT-K4.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Experimental investigation and thermodynamic assessment of phase equilibria in the GaTe–AgGa5Te8–Te system below 600 K

Equilibrium T–x space of the Ag–Ga–Te system in the GaTe–AgGa5Te8–Te part was divided below 600 K into three-phase regions Ga2Te5–AgGa5Te8–Te, Ga2Te3–AgGa5Te8–Ga2Te5, Ga7Te10–AgGa5Te8–Ga2Te3, Ga3Te4–AgGa5Te8–Ga7Te10, and GaTe–AgGa5Te8–Ga3Te4 by the electromotive force (EMF) method. To accomplish accurate experimental data, the following electrochemical cells (ECs) were assembled: (−)IE|NE|SSЕ|R{Ag+}|PЕ|IE(+), where IE is the inert electrode (graphite powder), NE is the negative electrode (silver powder), SSE is the solid-state electrolyte (glassy Ag3GeS3Br), PE is the positive electrode, R{Ag+} is the region of PE that contact with SSE. At the stage of cell preparation, PE is a nonequilibrium phase mixture of the well-mixed powdered compounds Ag2Te, GaTe, Ga2Te3, and tellurium, taken in ratios corresponding to two or three different points in each of the mentioned regions. The equilibrium set of phases was formed in the R{Ag+} region at 600 K for 48 h with the participation of the Ag+ ions. Silver cations, displaced for thermodynamic reasons from the NE to the PE of the ECs, acted as catalyst, i.e., small nucleation centers of equilibrium phases. The spatial position of the established three-phase regions relative to the silver point was used to assign the overall potential-determining reactions of synthesis of the ternary AgGa5Te8 and binary Ga2Te5, Ga7Te10, Ga3Te4 compounds. For the first time, the values of the standard thermodynamic functions (Gibbs energies, enthalpies, and entropies) of these compounds were determined based on the temperature dependences of the EMF of the ECs.

Silver Shell Thickness-Dependent Conductivity of Coatings Based on Ni@Ag Core@shell Nanoparticles.

Ink based on metallic nanoparticles has been widely used so far for the fabrication of electronic circuits and devices using printing technology. This study aimed at the analysis of the effect of the silver shell thickness of nickel@silver core@shell (Ni@Ag) nanoparticles (NPs) on the fabrication and conductive properties of deposited coatings. The process of the synthesis of Ni@Ag NPs with various silver shell thicknesses was developed. The physicochemical properties (size, stability against aggregation process) of synthesized Ni@Ag nanoparticles were analyzed. The films based on ink containing Ni@Ag NPs with different silver shell thicknesses were fabricated and sintered in a temperature range of 120-300 °C and at times from 15 to 90 min. The dependence of their conductive properties on the applied temperature and time as well as silver shell thickness was evaluated. Ni NPs were coated with 10, 20, 30, 35, 45, and 55 nm silver shell thickness. The resistivity of coatings based on obtained NPs depends on the thickness of the Ag shell and the sintering temperature. After sintering at 300 °C, the highest decrease in its value (at an optimal sintering time of 60 min) from about 100 µΩ·cm to 9 µΩ·cm was observed when the thickness of the shell increased from 10 to 55 nm. At the lowest sintering temperature (120 °C) the highest conductivity (about 50% of that for bulk nickel) was obtained for films based on Ni@Ag NPs with 45 and 55 nm of the silver shell thickness. The analysis of the resistivity of the sintered films showed that higher conductivity was obtained for the coatings formed from Ni@Ag NPs with the thicker Ag shell; moreover, thicker shells allowed a lowering of sintering temperature due to higher conductivity and a lower melting point of silver in comparison to nickel NPs.

Management of Silver Point Retrieval for Root canal Retreatment: A Case Report

The historical importance of the solid core material is decreasing. When greater, more precise preparation of the canal space was not possible due to inferior metallurgy and instrument design, it was frequently utilized in the past. Silver points were machined with a circular cross section and more frequently than not went into oval than round canals. Long-term success rates might not be as great, but some cases may defy the odds. The prognosis after treatment and follow up by phone five years after the completion of treatment. A 46-years-old Chinese female was referred from a general private practitioner for the endodontic management of 36. The tooth had been endodontically treated 30 years before; subsequently the patient complained of occasionally mild discomfort that last a few second without any stimulating factors at the lower left molar. Radiographic finding revealed that the tooth had been treated with silver points and associated with periapical radiolucency. Non-surgical root canal retreatment was performed for the tooth. Conclusions: Due to the nature of partially removal silver points, even though the prognosis is guarded at the time of obturation. After five years, it was considered favourable although it was extracted due to fracture.

Caesium- and sodium-filled pressure controlled heat pipe at NRC

What if you could tune the temperature of the fixed point used to calibrate your thermometer continuously between the freezing points of zinc (692.677 K) and silver (1234.93 K) while maintaining the uniform temperature environment (±10 mK) along 20 cm zone for hours at a time and with an uncertainty approaching a fraction of a mK? We are aiming to do exactly that by using a set of caesium- and sodium-filled pressure controlled heat pipes previously established at NRC. The original pressure controlled heat pipe furnaces have been recommissioned with a number of changes to improve their function as a calibration by comparison apparatus. In particular, the new gas handling system capable of controlling the pressure within ±4 ppm was installed side by side with the previously reported one. In this paper, we show the temperature performance of legacy NRC caesium- and sodium-filled pressure controlled heat pipes when connected to the new gas handling system.

Separation of Different Resin Plates Bonded by Solvent Through a Wire Explosion Induced by Pulsed Discharge

Accelerating the resource recycling of plastics and creating a recycling-oriented society require the development of efficient recycling technology for resin adhesives used in many products. We report the application of a fine wire explosion induced by an electric pulse to the selective separation of different resin adherends. Methylene dichloride, a solvent, was applied to the interface of an acrylic plate and polycarbonate plate together with a silver wire. A pulsed discharge circuit applied electric pulses to the fine wire and thus exploded the wire. At a capacitance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4~\mu \text{F}$ </tex-math></inline-formula> and charging voltage of 5.5 kV, no separation of different resin materials occurred. Shadowgraph visualization revealed that when a charging voltage of 20 kV was applied, separation at the interface of the bonded resin materials occurred due to gas expansion, resulting from vaporization of the exploding fine wire. Electrothermal simulation showed that the temperature within the silver wire reached the boiling point of silver when electric pulses were applied at a charging voltage of 20 kV, suggesting that the silver wire melted and evaporated under the effect of an electrothermal force, causing the silver wire to expand. In terms of separating different resin adherends at their interface using an electric pulse, it is effective to place a fine wire on the adhesive surface, bond the resin materials, and, through applying an electric pulse, generate Joule heat in the wire, expand gas in the wire, and vaporize the wire.

SIM Thermocouple Type S Supplementary Comparison

Main textA collapsed star type S thermocouple intercomparison was performed over the International Temperature Scale of 1990 (ITS-90) temperature range from 0 °C to 1100 °C. This was an Inter-American Metrology System (SIM) regional intercomparison piloted by the National Institute of Standards and Technology (NIST). Eleven laboratories (including NIST) participated in the intercomparison. Twenty-one type S thermocouples were constructed and calibrated at NIST, of which ten served as transfer standards. The thermocouples were identified as Cut 1 through Cut 21. Each thermocouple was calibrated by the metal fixed-point method at the freezing points of Zn, Al, Ag, and Au. The 21 calibrations were ultimately used to determine the reference values (RV) for the intercomparison. Subsequently the artifacts were calibrated at a participating laboratory by comparison with a local standard and/or by fixed-point method. Subsequently they were returned to the pilot laboratory where they were remeasured at the freezing point of silver (for purposes of determining a transfer uncertainty). Although thermocouples are not a standard interpolating instrument on the ITS-90, they are proposed as an approximation technique and are a widely used thermometer; so, it is useful to look at the measurement capabilities involved in their calibration.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Effects of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; sintering aid on properties of low temperature sintered Li-Zn microwave ferrites

With the progress of modern wireless communication technology, microwave communication devices are developing toward miniaturization and integration, and low-temperature co-firing ceramic/ferrite technology is the key to meet the above demands. In this paper, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (VA) sintering aid is used to realize low-temperature sintering (below melting point of silver that is 950 ℃) of Li-Zn microwave ferrite, which is suitable for radar phase shifter. In this work, firstly, Li-Zn ferrite pre-firing material is prepared by mechanochemical ball-milling method, and then VA composite is selected as sintering aid to prepare Li&lt;sub&gt;0.42&lt;/sub&gt;Zn&lt;sub&gt;0.27&lt;/sub&gt;Ti&lt;sub&gt;0.11&lt;/sub&gt;Mn&lt;sub&gt;0.1&lt;/sub&gt;Fe&lt;sub&gt;2.1&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; ferrite at low temperatures. The effects of adding amount of VA sintering aid and sintering temperature on crystal structure, microstructure and magnetic properties (saturation induction, coercivity, linewidth of ferromagnetic resonance, etc.) of the materials are also studied. The VA sintering aid can reduce the sintering temperature and maintain the spinel crystal structure of Li-Zn microwave ferrite, the diffraction peaks of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; involved in the sintering process are observed from none of the samples sintered at different temperatures, because the additive amount of VA sintering aid is very low compared with that of Li-Zn ferrite, so no corresponding impurity peaks are detected. The introduction of VA sintering aid can promote the grain growth, with the average grain size increasing from 0.92 μm to 9.74 μm. In the sintering process of Li-Zn ferrite, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; in VA sintering aid will melt first to form liquid phase due to its low melting point, which promotes the growth of grains. At the same time, Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; with higher melting point can inhibit the grain growth and make the grain uniform. It is worth noting that when excessive VA sintering aid is added, the grain size of ferrite will decrease instead, because too much VA sintering aid will form a large number of liquid phases around the grains, thus splitting the grains and hindering the further growth of the Li-Zn grains. Under the condition of optimal VA sintering aid addition (0.18%, weight percentage), the saturation induction of the sample increases from 144 mT to 281 mT; the rectangular ratio increases from 0.57 to 0.78; the coercivity decreases from 705 A/m to 208 A/m; the linewidth of ferromagnetic resonance decreases from 648 Oe to 247 Oe. In summary, VA sintering aid can effectively improve the properties of Li-Zn microwave ferrite, which has a positive significance in developing low- temperature co-firing ceramic/ferrite technology.

Origin of an Anticrossing between a Leaky Photonic Mode and an Epsilon-Near-Zero Point of Silver.

Strong light-matter coupling hybridizes light and matter to form states known as polaritons, which give rise to a characteristic anticrossing signature in dispersion plots. Here, we identify conditions under which an anticrossing can occur in the absence of strong coupling. We study planar silver/dielectric structures and find that, around the epsilon-near-zero point in silver, the impedance matching between the silver and dielectric layers gives rise to an anticrossing. Our work shows that care must be taken to ensure that anticrossing arising from impedance matching is not misattributed to strong coupling.

ТЕРМОДИНАМІЧНІ ВЛАСТИВОСТІ СПОЛУКИ AgGaGe3Se8 ЗА Т≤500 К, ВСТАНОВЛЕНІ МЕТОДОМ ЕРС

The division of the concentration space of the Ag–Ga–Ge–Se system in the GeSe–Se–Ga2Se3–AgGaGe3Se8–GeSe section was carried out by the EMF method. The concentration space of the Ag–Ga–Ge–Se system contains the four-phase regions GeSe2–Se–Ga2Se3–AgGaGe3Se8 (I) and GeSe–GeSe2–Ga2Se3–AgGaGe3Se8 (II). The spatial positions of these phase regions vs the point of silver were used to express equations of the overall cell reactions of synthesis of the AgGaGe3Se8 compound: 2Ag + 6GeSe2 + Ga2Se3 + Se = 2AgGaGe3Se8 and 2Ag + 7GeSe2 + Ga2Se3 = GeSe + 2AgGaGe3Se8. Reactions were performed in the positive electrodes of the following electrochemical cells (ECCs): (−) С | Ag | SЕ | R(Ag+) | PЕ | С (+), where C is graphite, Ag is the left (negative) electrode, SE is the purely Ag+ ion conducting solid electrolyte (Ag3GeS3Br-glass), PE is the right (positive) electrode, and R(Ag+) is the region of PE that contact with SE. Shifted from the left electrode to the R(Ag+) region for thermodynamic reasons Ag+ ions acted as the small nucleation centers for reconstruction of the metastable mixtures of compounds in the thermodynamically stable mixture of phases. Linear dependences of EMF vs temperature of ECCs were used to calculate the standard thermodynamic properties of the AgGaGe3Se8 equilibrium in the regions (I) and (II): ∆_f G_((I))^○= –(575,0 ± 8,9) kJ·mol −1, ∆_f H_((I))^○= –(574,7 ± 12,0) kJ·mol−1, S_((I))^○ = (515,9 ± 14,1) J·(mol·K)−1 and ∆_f G_((II))^○ = –(588,4 ± 9,4) kJ·mol−1, ∆_f H_((II))^○ = –(590,6 ± 12,9) kJ·mol−1, S_((II))^○ = (507,8 ± 13,2) J·(mol·K)−1, respectively. The relative difference between the calculated values ∆_f G_((I))^○ and ∆_f G_((II))^○ within ~2.3% and the overlap of the uncertainty intervals characterize the four-phase sections (I) and (II) by the combination of compounds of the formula composition. Moreover, values of the partial thermodynamic functions of the potential-determining component (Ag) of the AgGaGe3Se8 compound were calculated.

Theoretical prediction of melting curves of gold and silver up to pressure 150 GPa

We investigate melting curves of gold and silver thanks to the statistical moment method in quantum statistical mechanics and the modified Lindemann melting criterion. Numerical calculations have been performed for face-centered cubic (fcc) gold and silver metals up to pressure 150 GPa. Our results are compared with available experimental data and ab initio molecular dynamics simulations where possible. We show that theoretical melting line of gold goes along with recent X-ray diffraction measurements reported by Weck et al. up to pressure more than 110GPa. For silver, our work virtually coincides with the quantum molecular dynamics melting curve which is a combination of fcc and body-centered cubic (bcc) segments freshly implemented by Baty et al. At the pressure 94.2 GPa of the predicted fcc–bcc-liquid triple point of silver, our calculated melting temperature is 4302 K that is only about 2% difference from the prediction of Baty et al. This research proposes a relatively simple approach made from the modified Lindemann criterion and the moment method for predicting melting points of materials at high pressure.

Asia’s Silver Absorption through the Triangular Settlement System, 1846–1870

This study reveals the operation of the triangular settlement system for Asia’s silver absorption over the 1850s–60s, which contributed to the stabilization of the pre-1870 global monetary system. First, we demonstrate that the triangular settlement system among Britain, India, and China was established based on exchange operations. Second, we validate the bullion point method for Asia’s settlement analysis and devise the triangular silver point mechanism. Third, through reconstructing silver points and comparing the arbitrage profits with the silver trade, we found that silver was imported into Asia from Britain through both the bilateral and triangular settlement systems.

Solid-State-Activated Sintering of ZnAl2O4 Ceramics Containing Cu3Nb2O8 with Superior Dielectric and Thermal Properties

Low-temperature co-fired ceramics (LTCCs) are dielectric materials that can be co-fired with Ag or Cu; however, conventional LTCC materials are mostly poorly thermally conductive, which is problematic and requires improvement. We focused on ZnAl2O4 (gahnite) as a base material. With its high thermal conductivity (~59 W·m−1·K−1 reported for 0.83ZnAl2O4–0.17TiO2), ZnAl2O4 is potentially more thermally conductive than Al2O3 (alumina); however, it sinters densely at a moderate temperature (~1500 °C). The addition of only 4 wt.% of Cu3Nb2O8 significantly lowered the sintering temperature of ZnAl2O4 to 910 °C, which is lower than the melting point of silver (961 °C). The sample fired at 960 °C for 384 h exhibited a relative permittivity (εr) of 9.2, a quality factor by resonant frequency (Q × f) value of 105,000 GHz, and a temperature coefficient of the resonant frequency (τf) of −56 ppm·K−1. The sample exhibited a thermal conductivity of 10.1 W·m−1·K−1, which exceeds that of conventional LTCCs (~2–7 W·m−1·K−1); hence, it is a superior LTCC candidate. In addition, a mixed powder of the Cu3Nb2O8 additive and ZnAl2O4 has a melting temperature that is not significantly different from that (~970 °C) of the pristine Cu3Nb2O8 additive. The sample appears to densify in the solid state through a solid-state-activated sintering mechanism.

Effects of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; sintering aid on properties of low temperature sintered Li-Zn microwave ferrites

With the progress of modern wireless communication technology, microwave communication devices are developing toward miniaturization and integration, and low temperature co-firing ceramic/ferrite technology is the key to meet the above demands. In this paper, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (VA) sintering aid is used to realize low temperature sintering (below melting point of silver that is 950 ℃) of Li-Zn microwave ferrite, which is suitable for radar phase shifter. In this paper, firstly, Li-Zn ferrite pre-firing material is prepared by mechanochemical ball milling method, and then VA composite is selected as sintering aid to prepare Li&lt;sub&gt;0.42&lt;/sub&gt;Zn&lt;sub&gt;0.27&lt;/sub&gt;Ti&lt;sub&gt;0.11&lt;/sub&gt;Mn&lt;sub&gt;0.1&lt;/sub&gt;Fe&lt;sub&gt;2.1&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; ferrite at low temperatures. The effects of adding amount of VA sintering aid and sintering temperature on crystal structure, microstructure and magnetic properties (saturation induction, coercivity, linewidth of ferromagnetic resonance, et al.) of the materials are also studied. The VA sintering aid can reduce the sintering temperature and maintain the spinel crystal structure of Li-Zn microwave ferrite, the diffraction peaks of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; involved in the sintering process are not observed for all the samples sintered at different temperatures, because the mass ratio of V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; in VA sintering aid is very low compared with Li-Zn ferrite, so there are no corresponding impurity peaks. The introduction of VA sintering aid can promote the grain growth, with the average grain size increasing from 0.92 mm to 9.74 mm. In the sintering process of Li-Zn ferrite, V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; in VA sintering aid will melt first to form liquid phase due to its low melting point, which promotes the growth of grains. At the same time, Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; with higher melting point can inhibit the grain growth and make the grain uniform. It is worth noting that when excessive VA sintering aid is added, the grain size of ferrite will decrease instead, because too much VA sintering aid will form a large number of liquid phases around the grains, thus splitting the grains and hindering the further growth of the Li-Zn grains. Under the condition of optimal VA sintering aid addition (0.18 &lt;em&gt;wt. &lt;/em&gt;%), the saturation induction of the sample increased from 144 mT to 281 mT; The rectangular ratio increased from 0.57 to 0.78; The coercivity decreased from 705 A/m to 208 A/m; The linewidth of ferromagnetic resonance decreased from 648 Oe to 247 Oe. In summary, VA sintering aid can effectively improve the properties of Li-Zn microwave ferrite, which has a positive significance for the development of low temperature co-firing ceramic/ferrite technology.

Realisation of the ITS-90 and thermodynamic temperature measurements above 960 °C using a monochromator-based radiance comparator

At LNE-Cnam, the international temperature scale of 1990 (ITS-90) and thermodynamic temperature measurements above the silver point, are carried out with a radiance comparator. This instrument is, more generally, devoted to any radiance comparison in temperature range from the ambient to 3000 °C. The instrument developed in the early 1990s at LNE-Cnam has the advantage of being completely adjustable. Compared to compact radiation thermometers based on lenses and a narrow-band interference filter, the radiance comparator is only made of gold coated mirrors and a Czerny–Turner monochromator to select the spectral bandwidth. The instrument offers the possibility to tune the geometric extent and the slit scattering function. In return, the radiance comparator is a complex instrument that requires a complete and a regular characterisation at the highest level of accuracy. In the first part, this paper describes the instrument and its operating principle. In a second part, a complete study of the wavelength calibration, the slit scattering function, size of source effect, out-of-band transmittance, linearity and other main sources of uncertainty are presented and discussed. Their associated uncertainties are estimated separately and are grouped together to give an example of propagation of uncertainties when realising the ITS-90.

Doping potassium niobate with transition metals enhances its photocatalytic properties

Replacing some niobate ions with silver and manganese points to new directions for environmental materials aimed at curbing pollution by splitting water.