SR-rich Region Research Articles

Association of SARS-CoV-2 Nucleocapsid Protein Mutations with Patient Demographic and Clinical Characteristics during the Delta and Omicron Waves.

SARS-CoV-2 genomic mutations outside the spike protein that may increase transmissibility and disease severity have not been well characterized. This study identified mutations in the nucleocapsid protein and their possible association with patient characteristics. We analyzed 695 samples from patients with confirmed COVID-19 in Saudi Arabia between 1 April 2021, and 30 April 2022. Nucleocapsid protein mutations were identified through whole genome sequencing. 𝜒2 tests and t tests assessed associations between mutations and patient characteristics. Logistic regression estimated the risk of intensive care unit (ICU) admission or death. Of the 60 mutations identified, R203K was the most common, followed by G204R, P13L, E31del, R32del, and S33del. These mutations were associated with reduced risk of ICU admission. P13L, E31del, R32del, and S33del were also associated with reduced risk of death. By contrast, D63G, R203M, and D377Y were associated with increased risk of ICU admission. Most mutations were detected in the SR-rich region, which was associated with low risk of death. The C-tail and central linker regions were associated with increased risk of ICU admission, whereas the N-arm region was associated with reduced ICU admission risk. Consequently, mutations in the N protein must be observed, as they may exacerbate viral infection and disease severity. Additional research is needed to validate the mutations' associations with clinical outcomes.

Dominant clade-featured SARS-CoV-2 co-occurring mutations reveal plausible epistasis: An in silico based hypothetical model.

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has evolved into eight fundamental clades with four of these clades (G, GH, GR, and GV) globally prevalent in 2020. To explain plausible epistatic effects of the signature co‐occurring mutations of these circulating clades on viral replication and transmission fitness, we proposed a hypothetical model using in silico approach. Molecular docking and dynamics analyses showed the higher infectiousness of a spike mutant through more favorable binding of G614 with the elastase‐2. RdRp mutation p.P323L significantly increased genome‐wide mutations (p < 0.0001), allowing for more flexible RdRp (mutated)‐NSP8 interaction that may accelerate replication. Superior RNA stability and structural variation at NSP3:C241T might impact protein, RNA interactions, or both. Another silent 5′‐UTR:C241T mutation might affect translational efficiency and viral packaging. These four G‐clade‐featured co‐occurring mutations might increase viral replication. Sentinel GH‐clade ORF3a:p.Q57H variants constricted the ion‐channel through intertransmembrane–domain interaction of cysteine(C81)‐histidine(H57). The GR‐clade N:p.RG203‐204KR would stabilize RNA interaction by a more flexible and hypo‐phosphorylated SR‐rich region. GV‐clade viruses seemingly gained the evolutionary advantage of the confounding factors; nevertheless, N:p.A220V might modulate RNA binding with no phenotypic effect. Our hypothetical model needs further retrospective and prospective studies to understand detailed molecular events and their relationship to the fitness of SARS‐CoV‐2.

K2NiF4 type oxides, Ln2-xSrxNiO4+δ (Ln = La and Pr; x = 0–1.4) as an oxygen electrocatalyst for aqueous lithium–oxygen rechargeable batteries

The structural and electrochemical characteristics of the Ln2-xSrxNiO4+δ (Ln = La and Pr; x = 0–1.4) system were investigated to clarify the relationship between the electrocatalytic activity and various characteristics such as the structure, composition, electrical conductivity, and oxygen content. Rietveld analysis of the powder X-ray diffraction (XRD) data showed that the tetragonal distortion of the NiO6 octahedra decreased monotonically with an increase of x, while the Ln (Sr)–O (//c-axis) in the rock-salt block was expanded with an increase in x, although the tetragonality, c/a showed a maximum at x = 0.6. Cyclic voltammetry (CV) measurements showed that the activity for the oxygen evolution reaction (OER) increased with x, while that of the oxygen reduction reaction (ORR) was independent of x. The characteristic peak due to oxygen insertion into the lattice was observed at ca. 1.45 V vs. RHE, the intensity of which increased with the Sr content, which reflects the increase in the internal chemical diffusion of oxygen species. X-ray photoelectron spectroscopy (XPS) measurements for the constituent elements confirmed the presence of OH− groups inside the catalyst particles, especially in the Sr-rich region. It is suggested that the reversible intercalation ability of the OH− group into the rock-salt layer in the Ruddlesden-Popper (RP) phase (An+1BnO3n+1) contributes significantly to the improvement of the OER activity.

Temporal landscape of mutational frequencies in SARS-CoV-2 genomes of Bangladesh: possible implications from the ongoing outbreak in Bangladesh.

Along with intrinsic evolution, adaptation to selective pressure in new environments might have resulted in the circulatory SARS-CoV-2 strains in response to the geoenvironmental conditions of a country and the demographic profile of its population. With this target, the current study traced the evolutionary route and mutational frequency of 198 Bangladesh-originated SARS-CoV-2 genomic sequences available in the GISAID platform over a period of 13 weeks as of 14 July 2020. The analyses were performed using MEGA X, Swiss Model Repository, Virus Pathogen Resource and Jalview visualization. Our analysis identified that majority of the circulating strains strikingly differ from both the reference genome and the first sequenced genome from Bangladesh. Mutations in nonspecific proteins (NSP2-3, NSP-12(RdRp), NSP-13(Helicase)), S-Spike, ORF3a, and N-Nucleocapsid protein were common in the circulating strains with varying degrees and the most unique mutations (UM) were found in NSP3 (UM-18). But no or limited changes were observed in NSP9, NSP11, Envelope protein (E) and accessory factors (NSP7a, ORF 6, ORF7b) suggesting the possible conserved functions of those proteins in SARS-CoV-2 propagation. However, along with D614G mutation, more than 20 different mutations in the Spike protein were detected basically in the S2 domain. Besides, mutations in SR-rich region of N protein and P323L in RDRP were also present. However, the mutation accumulation showed a significant association (p = 0.003) with sex and age of the COVID-19-positive cases. So, identification of these mutational accumulation patterns may greatly facilitate vaccine development deciphering the age and the sex-dependent differential susceptibility to COVID-19.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11262-021-01860-x.

The Mechanism of SARS-CoV-2 Nucleocapsid Protein Recognition by the Human 14-3-3 Proteins

The coronavirus nucleocapsid protein (N) controls viral genome packaging and contains numerous phosphorylation sites located within unstructured regions. Binding of phosphorylated SARS-CoV N to the host 14-3-3 protein in the cytoplasm was reported to regulate nucleocytoplasmic N shuttling. All seven isoforms of the human 14-3-3 are abundantly present in tissues vulnerable to SARS-CoV-2, where N can constitute up to ~1% of expressed proteins during infection. Although the association between 14-3-3 and SARS-CoV-2 N proteins can represent one of the key host-pathogen interactions, its molecular mechanism and the specific critical phosphosites are unknown. Here, we show that phosphorylated SARS-CoV-2 N protein (pN) dimers, reconstituted via bacterial co-expression with protein kinase A, directly associate, in a phosphorylation-dependent manner, with the dimeric 14-3-3 protein, but not with its monomeric mutant. We demonstrate that pN is recognized by all seven human 14-3-3 isoforms with various efficiencies and deduce the apparent KD to selected isoforms, showing that these are in a low micromolar range. Serial truncations pinpointed a critical phosphorylation site to Ser197, which is conserved among related zoonotic coronaviruses and located within the functionally important, SR-rich region of N. The relatively tight 14-3-3/pN association could regulate nucleocytoplasmic shuttling and other functions of N via occlusion of the SR-rich region, and could also hijack cellular pathways by 14-3-3 sequestration. As such, the assembly may represent a valuable target for therapeutic intervention.

Evolutionary dynamics of SARS-CoV-2 nucleocapsid protein and its consequences.

The emerged novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a global health crisis that warrants an accurate and detailed characterization of the rapidly evolving viral genome for understanding its epidemiology, pathogenesis, and containment. Here, we explored 61,485 sequences of the nucleocapsid (N) protein, a potent diagnostic and prophylactic target, for identifying the mutations to review their roles in real-time polymerase chain reaction based diagnosis and observe consequent impacts. Compared to the Wuhan reference strain, a total of 1034 unique nucleotide mutations were identified in the mutant strains (49.15%, n = 30,221) globally. Of these mutations, 367 occupy primer binding sites including the 3'-end mismatch to the primer-pair of 11 well-characterized primer sets. Noteworthily, CDC (USA) recommended the N2 primer set contained a lower mismatch than the other primer sets. Moreover, 684 amino acid (aa) substitutions were located across 317 (75.66% of total aa) unique positions including 82, 21, and 83 of those in theRNA binding N-terminal domain (NTD), SR-rich region, and C-terminal dimerization domain, respectively. Moreover, 11 in-frame deletions, mostly (n = 10) within the highly flexible linker region, were revealed, and the rest was within the NTD region. Furthermore, we predicted the possible consequence of high-frequency mutations (≥20) and deletions on the tertiary structure of the N protein. Remarkably, we observed that a high frequency (67.94% of mutated sequences) co-occuring mutations (R203K and G204R) destabilized and decreased overall structural flexibility. The N protein of SARS-CoV-2 comprises an average of 1.2 mutations per strain compared to 4.4 and 0.4 in Middle East respiratory syndrome-related coronavirus and SARS-CoV, respectively. Despite being proposed as the alternativetarget to spike protein for vaccine and therapeutics, the ongoing evolution of the N protein may challenge these endeavors, thus needing further immunoinformatics analyses. Therefore, continuous monitoring is required for tracing the ongoing evolution of the SARS-CoV-2 N protein in prophylactic and diagnostic interventions.

BioAider: An efficient tool for viral genome analysis and its application in tracing SARS-CoV-2 transmission

The novel human coronavirus (SARS-CoV-2) causes the coronavirus disease 2019 (COVID-19) pandemic worldwide. Control of COVID-19 pandemic is vital for public health and is the prerequisite to maintain social stability. However, the origin and transmission route of SARS-CoV-2 is unclear, bringing huge difficult to virus control. Monitoring viral variation and screening functional mutation sites are crucial for prevention and control of infectious diseases. In this study, we developed a user-friendly software, named BioAider, for quick sequence annotation and mutation analysis on large-scale genome-sequencing data. Herein, we detected 14 substitution hotspots within 3,240 SARS-CoV-2 genome sequences, including 3 groups of potentially linked substitution. NSP13-Y541C was crucial substitution which might affect the unwinding activity of the viral helicase. In particular, we discovered a SR-rich region of SARS-CoV-2 distinct from SARS-CoV, indicating more complex replication mechanism and unique N-M interaction of SARS-CoV-2. Interestingly, the quantity of SSRX repeat fragments in SARS-CoV-2 provided further evidence of its animal origin. Overall, we developed an efficient tool for rapid identification of viral genome mutations which could facilitate viral genomic studies. Using this tool, we have found critical clues for the transmission route of SARS-CoV-2 which would provide theoretical support for the epidemic control of pathogenic coronaviruses.

Mutations in SARS-CoV-2 viral RNA identified in Eastern India: Possible implications for the ongoing outbreak in India and impact on viral structure and host susceptibility

Direct massively parallel sequencing of SARS-CoV-2 genome was undertaken from nasopharyngeal and oropharyngeal swab samples of infected individuals in Eastern India. Seven of the isolates belonged to the A2a clade, while one belonged to the B4 clade. Specific mutations, characteristic of the A2a clade, were also detected, which included the P323L in RNA-dependent RNA polymerase and D614G in the Spike glycoprotein. Further, our data revealed emergence of novel subclones harbouring nonsynonymous mutations, viz. G1124V in Spike (S) protein, R203K, and G204R in the nucleocapsid (N) protein. The N protein mutations reside in the SR-rich region involved in viral capsid formation and the S protein mutation is in the S2 domain, which is involved in triggering viral fusion with the host cell membrane. Interesting correlation was observed between these mutations and travel or contact history of COVID-19 positive cases. Consequent alterations of miRNA binding and structure were also predicted for these mutations. More importantly, the possible implications of mutation D614G (in SD domain) and G1124V (in S2 subunit) on the structural stability of S protein have also been discussed. Results report for the first time a bird’s eye view on the accumulation of mutations in SARS-CoV-2 genome in Eastern India. Electronic supplementary materialThe online version of this article (10.1007/s12038-020-00046-1) contains supplementary material, which is available to authorized users.

Magnetic properties of perovskite Ca1−xSrxFeO3

We synthesized Ca1−xSrxFeO3 containing tetravalent iron Fe4+ with high valence by low temperature heat treatment along with ozone oxidization. We investigated the magnetic properties of perovskite Ca1−xSrxFeO3. The charge disproportionation transition temperature (TCD) of Ca1−xSrxFeO3 was observed from x = 0.0 to 0.6 in the magnetic susceptibility measurements. The decrease in TCD occurs is attributed to deformation of the crystal structure. The metamagnetic transitions with hysteresis were observed in the magnetization curves of all the compositions. The metamagnetic behavior is due to helical magnetism, which means that there are intermediate stable states before magnetization is saturated. In the Sr-rich region with x = 0.8 and 1.0, the saturation magnetization shows forced ferromagnetic order with a value of ∼3.2 μB at high magnetic field, H ∼ 60 T.

HR-TEM study of oxygen vacancy ordered Sr4+nMn4+nO10+3n compounds

The study of oxygen vacancy ordering in the LaxSr1-xMnOy system has shown a strong correlation between Mn formal valence and coordination to oxygen. The Mn2+ was found forming octahedra (Oc) and tetrahedra (Te), Mn3+ octahedra and pyramids (Py) and Mn4+ only octahedra. This tendency was derived from the presence of three kinds of vacancy orderings in the system. For y&gt;2.5 and the average Mnm+ charge of 2&lt;m&lt;3 (x&gt;0.5), brownmillerite-type structures are found with Mn2+/3+ Oc and Mn2+ Te. [1] For 3&lt;m&lt;4 (x&lt;0.5) structures of the homologous Sr4+nMn4+nO10+3n –type series are found with Mn3+ Py and Mn3+/4+ Oc. [2] For y&lt;2.5 and 2&lt;m&lt;3 (x&lt;0.5) a complex layered structure with OcTeOcOcTe'Oc ordering and step defects of Mn3+ Py and Mn2+ Te [3] is observed. Brownmillerite-type structure is absent in the Sr-rich region since mostly Mn3+ is present, which does not show tendency to form Te. Compounds of the Sr4+nMn4+nO10+3n series have been described as arrangements of groups of four Py and n Oc in symmetrical patterns. [2] This description did not elucidate the crystal chemistry reasons for specific pattern (n=0, 1 and 3) since it neglected the coordination stabilization associated with oxygen vacancy, charge and orbital ordering observed in the structures.[2] Using high-resolution transmission electron microscopy (HR-TEM) for SrMnOy with y values located between corresponding n=0, 1 and 3 compositions, we have determined that the oxygen vacancy ordering directs the formation of these patterns. The structural patterns can be described as perovskites with lines of oxygen vacancies along [001] with nearest lines of vacancies in the cubic (310) plane. Successive (310) planes are n perovskite blocks (Oc) apart in the [010] direction. This ordering pattern allows the coherent growth of phases with different n at the sides of (310) plane as observed in grains of a sample of SrMnO2.668 where n=1 and n=3 phases grown coherently one at each side of the vacancy plane.

Impact of Local Lattice Disorder on Spin and Orbital Orders in Ca2-xSrxRuO4

We have studied relationship between local lattice disorder, Ru 4$d$ spin-orbit interaction, and global spin/orbital orders of Ca$_{2-x}$Sr$_x$RuO$_4$ in the Sr-rich and Ca-rich regions of its phase diagram by using unrestricted Hartree-Fock calculation on a $8\times8$ RuO$_4$ lattice model. The calculations show that the local elongation of RuO$_6$ octahedron in an antiferromagnetic insulator Ca$_2$RuO$_4$ induces local orbital change with making the Mott gap narrower. On the other hand, local compression of RuO$_6$ octahedron in a paramagnetic metal Sr$_2$RuO$_4$ induces global antiferromagnetic or ferromagnetic states. This result is consistent with a recent systematic $\mu$SR study by Carlo {\it et al.} which has revealed the static antiferromagnetic order at low temperature in the Sr-rich region.

CaAg – SrAg – BaAg: Zwischen CrB‐ und FeB‐Strukturtyp

AbstractCaAg – SrAg – BaAg: Between CrB and FeB Structure TypeDepending on both electronic (valence electron numbers) and geometric (atom size ratios) characteristics of the contributing elements, the 1:1 compounds AIIM of the heavier alkaline earth elements A and electron‐rich transition metals M form the well known CrB or FeB structure types. Both structure types exhibit M zig‐zag chains, which are stacked in different orientations against each other. In systematic studies of the pseudo‐binary sections CaxSr1−xAg and SrxBa1−xAg three new ternary phases with different stacking variants between the CrB (cubic stacking, c) and the FeB (hexagonal stacking, h2) structure type have been prepared and determined on the basis of single crystal x‐ray data. Starting from CaAg (CrB type, stacking c), up to 25 percent of Sr (i.e. in Ca0.75(2)Sr0.25(2)Ag: orthorhombic, space group Cmcm, a = 413.4(1), b = 1157.8(3), c = 467.4(2) pm, Z = 4, R1 = 0.0453) can be substituted without a change in the structure type. At a 1:1 ratio of Ca and Sr, a new structure type with stacking sequence (hc5)2 is formed (Ca0.48(3)Sr0.52(3)Ag: space group Pnma, a = 4800.1(1), b = 471.8(12), c = 624.11(9) pm, Z = 24, R1 = 0.0881). Further reduced cubic stacking ((hc2)2) is observed in the Sr rich region with Ca proportions between 39 and 25(2) % (space group Pnma, x = 0.39(1)/0.25(2): a = 2412.2(3)/2434.67(4), b = 472.75(5)/473.97(8), c = 626.17(7)/629.2(3) pm, Z = 12, R1 = 0.0430/0.0489) where the HT‐TbNi structure type is formed. The stability range of the SrAg structure type ((hc)2) starts at a Ca content of 5 % (Ca0.05Sr0.95Ag: space group Pnma, a = 1643.1(2), b = 476.79(7), c = 636.27(9) pm, Z = 8, R1 = 0.0318). From a new second modification of SrAg (space group Pnma, a = 4131.5(4), b = 478.79(6), c = 638.81(6) pm, Z = 20, R1 = 0.0394) up to a Ba proportion of 8 percent, the α‐CaCu structure type with sequence (hch2c)2 is formed. The stability range of the FeB structure with purely hexagonal stacking extends from Sr0.84(1)Ba0.16(1)Ag (a = 830.78(12), b = 479.35(8), c = 644.93(11) pm, Z = 4, R1 = 0.0413) to the border phase BaAg. In an accompanying computational study, the chemical bonding in the binary compounds CaAg, SrAg and BaAg is analyzed using FP‐LAPW band structure methods. Together with geometrical criteria, the results are used to compare and discuss the stability of the different stacking variants of the polar intermetallic 1:1 phases inbetween the CrB and the FeB structure type.

NSSRs/TASRs/SRp38s function as splicing modulators via binding to pre‐mRNAs

The genes for neural-salient serine/arginine-rich (NSSR) proteins 1 and 2 have been cloned from the neuronal differentiated embryocarcinoma cell line, P19. NSSRs contain an RNA recognition motif (RRM) at the N-terminal and several SR rich regions at the C-terminal resembling RS domains. We found that NSSRs associated with U1-70k, and determined the exon inclusion activity of NSSRs' C-terminals. First, the RRM was changed to the MS2 coat protein (MS2CP) and then, MS2 RNA stem-loops were inserted in the middle of the exon N of the clathrin light chain B minigene as an artificial exonic splicing enhancer to be recognized by the MS2CP. The modified exon N of the pre-mRNA was included by the MS2CP switched NSSR 1, but it was excluded by the MS2CP switched NSSR 2. The deletion analysis of the MS2CP switched NSSR 1 showed that the middle SR rich region was responsible for the activity of the modified exon N inclusion. Furthermore, the RRM domain of NSSRs recognized mRNAs. NSSRs were expressed in the nervous system, especially in cerebellar and hippocampal primordia, ventricular zone of the neocortex and olfactory bulb primordia, retina, and olfactory epithelium at E15.5, all containing undifferentiated neural stem cells. Taken together, our results showed that NSSRs modulate alternative splicing via binding to premRNAs during neural differentiation.

Phase relations and lattice parameters in the system SrO–BaO–Nb 2O 5 focusing on SBN (Sr xBa 1− xNb 2O 6)

In this paper we report the phase relations of the tetragonal tungsten bronze type strontium barium niobate (Sr x Ba 1− x Nb 2O 6) solid solution in the temperature range from 1200°C to 1450°C. The x-value depends on the synthesis temperature and reaches from 0.19 ⩽ x ⩽ 0.62 at 1200°C up to 0.18 ⩽ x ⩽ 0.84 at 1440°C. In addition lattice parameters of the stable phases at 1300°C depending on their chemical compositions are given. Samples with different SrO:BaO:Nb 2O 5 ratios were sintered in vertical tube furnaces at suitable temperatures in air. The chemical composition of the quenched equilibrated phase associations were determined by EPMA. Lattice parameters of the resulting crystalline phases were derived from refinement of d-values from XRD patterns. The phase field of SBN is strongly temperature dependent. The Ba-rich end-member of the solid solution contains 80 mol% Ba and 20 mol% Sr independently of the synthesis temperature. On the other hand the maximum Sr-content of the solid solution increases with temperature from 62 mol% Sr at 1200°C up to 84 mol% Sr at 1450°C. Also the Nb-content varies with temperature especially at synthesis temperatures below 1400°C. In particular at 1300°C the solid solution field of SBN extents to higher Nb-contents on the Ba-rich side leading to a Sr-free end-member of the solid solution. For this Ba-rich side of the solid solution series a substitutional formula Ba 4Sr 1 −y Nb y Nb 10O 30+1.5 y (0 ⩽ y ⩽ 1) can be given. A new compound (Sr, Ba) 5Nb 8O 25 in the SrO–BaO–Nb 2O 5 system has been found, exhibiting also a solid solution range. Chemical compositions of some previously described phases could be determined in more detail. The lattice parameters of the tetragonal tungsten bronze cell (A1 2A2 4C 4M1 2M2 8O 30) depend on the chemical composition of the solid solution. In the Sr-rich region and at low Nb-contents the a-parameter shifts strongly while on the Ba-rich side and at high Nb-contents the variation is lower. The c-parameter increases with the Ba-content.

The Structure Analysis and Antigenicity Study of the N Protein of SARS-CoV

The Coronaviridae family is characterized by a nucleocapsid that is composed of the genome RNA molecule in combination with the nucleoprotein (N protein) within a virion. The most striking physiochemical feature of the N protein of SARS-CoV is that it is a typical basic protein with a high predicted pI and high hydrophilicity, which is consistent with its function of binding to the ribophosphate backbone of the RNA molecule. The predicted high extent of phosphorylation of the N protein on multiple candidate phosphorylation sites demonstrates that it would be related to important functions, such as RNA-binding and localization to the nucleolus of host cells. Subsequent study shows that there is an SR-rich region in the N protein and this region might be involved in the protein-protein interaction. The abundant antigenic sites predicted in the N protein, as well as experimental evidence with synthesized polypeptides, indicate that the N protein is one of the major antigens of the SARS-CoV. Compared with other viral structural proteins, the low variation rate of the N protein with regards to its size suggests its importance to the survival of the virus.

Preparation and characterization of Sr2 –xLaxFeO4(0 ⩽x⩽ 1)

Solid-solution Sr2 –xLaxFeO4 crystallizing in the K2NiF4 structure has been obtained for 0 ⩽x⩽ 1. In the Sr-rich region, the K2NiF4 structure was stable only at low temperature. Heat treatment under an oxygen pressure of 100-500 atm was carried out to form oxygen stoichiometric samples. The structure was refined by the Rietveld method assuming space group I4/mmm. The FeO6 octahedron in Sr2FeO4 showed almost cubic symmetry, the La substitution causing an increase in the Fe–O (apical) length without modifying the a-axis length. All the samples showed semiconducting behaviour and positive Seebeck coefficients. An antiferromagnetic transition at 60 K was observed for Sr2FeO4, becoming obscure with increasing La content. The room-temperature Mossbauer spectra showed a symmetric singlet due to Fe4+ and a doublet due to Fe3+, except for Sr2FeO4 which showed a quadrupole doublet.

Improved Electrical Properties of SrTiO3, Thin Films by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition

ABSTRACTSrTiO3 thin films with various compositions have been prepared on Pt coated sapphire substrates by electron cyclotron resonance plasma chemical vapor deposition at 450 °C and 600 °C. The stoichiometric (Sr/(Sr+Ti)=0.50) films have maximum dielectric constants (εr) of 190 for the 600 °C deposition and 170 for the 450 °C deposition. The dielectric constant decreases abruptly with increasing or decreasing the Sr/(Sr+Ti) value from the stoichiometry, especially for the 450 °C deposition. The Ti-rich films include titanium suboxide (TiOx). In the Sr-rich films, excess SrO is thought to be inserted into the SrO plane and TiO2 plane in SrTiO3. In addition, SrCO3 is included in Sr-rich films. The concentration of these impurities is greater for the 450 °C deposition than for the 600 °C deposition. The leakage current density increases with increasing the Sr/(Sr+Ti) value, and the leakage current density for the 450 °C deposition is larger than for the 600 °C deposition in the Sr-rich composition region. These impurity phases may be related to the higher leakage current density. These results suggest that precise composition control in stoichiometry is necessary to deposit SrTiO3 films with superior electrical properties.

Newly developed ternary (Ca, Sr, Ba) zirconate ceramic system for microwave resonators

Abstract In Ca, Sr-rich region with orthorhombic perovskite-type structure, successful results such as high dielectric Q (2000∼3000 at 11GHz), suitable dielectric constant, (29∼32) and widely adjustable temperature coefficient of dielectric constant (−50 to +50 ppm/°C) were obtained. It was also found that substitution of small amounts of Ti for Zr brings some decrease in temperature coefficient with increase in dielectric Q. Using above described ceramics in microwave integrated circuits oscillator with GaAs FET, a compensation for temperature dependence of circuit elements was well achieved within the value which corresponds to the deviation of oscillation frequency within ± 500KHz at 11.66GHz (−20∼+60°C).