Ba Sr Research Articles

Tunable bulk acoustic wave resonators based on Ba<sub>0.25</sub>Sr<sub>0.75</sub>TiO<sub>3</sub> thin films and a HfO<sub>2</sub>/SiO<sub>2</sub> bragg reflector

A switchable and tunable bulk acoustic wave resonator based on a paraelectric phase Ba(0.25)Sr(0.75)TiO(3) thin film and an all-dielectric HfO(2)/SiO(2) Bragg reflector is presented. The achieved tuning range (3.8%) and effective electromechanical coupling coefficient (7.1%) are the highest reported for solidly mounted tunable bulk acoustic wave resonators. The non-conductive Bragg reflector stack provides excellent integration possibilities.

Sources of devonian magmatism in the Minusa Trough based on geochemical and Sr-Nd isotopic characteristics of basites

The results of geochemical and isotopic (Sr-Nd) studies of the rocks comprising the structure of igneous associations of Minusa Trough are presented. They allowed us to identify the heterogeneity of igneous sources. Similar heterogeneity is determined by mixing of at least two sources of source melts. The first one corresponds, by the geochemical parameters, to the OIB composition with a high content of noncoherent lithophile elements and to the PREMA-type mantle in its isotopic parameters. Another source is comparable to the lithospheric mantle that was metasomatized in above-subduction conditions. Participation of a second source melt in magma formation led to the appearance of IAB geochemical features (typical depletion in high-charge hydrophobic Ti, Nb, and Ta, and enrichment in Ba, common and radiogenic Sr) for basite melts. The performed studies give us ground to attribute the magmatism of Minusa Trough to the Altai-Sayan plume evolution beneath the convergent boundary within the limits of the southwestern margin of the Siberian continent.

Structural and mechanical properties characterization of barium strontium titanate (BST) ceramics

Ba(1-x)Sr(x)TiO3 ceramics, where x = 0.05, 0.10, 0.15, and 0.20, were prepared by solid state reaction technique. X-ray diffraction analysis confirmed the formation of single phase perovskite structures. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz. Investigations of ceramic microstructures and mechanical properties showed its dependence on composition and sintering time. Increasing of Sr content, x, resulted in a decrease in bulk density and ultrasonic attenuation and an increase in velocity and modulus. Also, size of crystallites and c/a ratio were found to decrease with increasing of x, and increased with increasing of sintering time. High temperature ultrasonic studies showed, in addition to Curie phase transition, two relaxation peaks and its origin was investigated. The acquired structural and mechanical results were correlated and discussed.

Terahertz dielectric response of ferroelectric baxsr1-xtio3thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

Complete erasing of ghost images on computed radiography plates and role of deeply trapped electrons

Abstract Computed radiography (CR) plates made of europium-doped Ba(Sr)FBr(I) were simultaneously exposed to filtered ultraviolet light and visible light in order to erase ghost images, i.e., latent image that is unerasable with visible light (LIunVL) and reappearing one, which are particularly observed in plates irradiated with a high dose and/or cumulatively over-irradiated. CR samples showing LIunVLs were prepared by irradiating three different types of CR plates (Agfa ADC MD10, Kodak Directview Mammo EHRM2, and Fuji ST-VI) with 50 kV X-ray beams in the dose range 8.1 mGy—8.0 Gy. After the sixth round of simultaneous 6 h exposures to filtered ultraviolet light and visible light, all the LIunVLs in the three types of CR plates were erased to the same level as in an unirradiated plate and no latent images reappeared after storage at 0 °C for 14 days. With conventional exposure to visible light, LIunVLs consistently remained in all types of CR plates irradiated with higher doses of X-rays and latent images reappeared in the Agfa M10 plates after storage at 0 °C. Electrons trapped in deep centers cause LIunVLs and they can be erased by simultaneous exposures to filtered ultraviolet light and visible light. To study electrons in deep centers, the absorption spectra were examined in all types of irradiated CR plates by using polychromatic ultraviolet light from a deep-ultraviolet lamp. It was found that deep centers showed a dominant peak in the absorption spectra at around 324 nm for the Agfa M10 and Kodak EHRM2 plates, and at around 320 nm for the Fuji ST-VI plate, in each case followed by a few small peaks. The peak heights were dose-dependent for all types of CR samples, suggesting that the number of electrons trapped in deep centers increases with the irradiation dose.

Tunable capacitors employing BZN/BST thin films for RF applications

Tunable parallel-plate capacitors employing Bi(1.5)Zn(1.0)Nb(1.5)O(7)/Ba(0.5)Sr(0.5)TiO(3) (BZN/BST) thin films for RF applications are reported. The intermediate frequency measurements indicate that the BZN/BST-based varactors demonstrate large tunability of 39% at 40 V and high device quality factor of 300 at 1 MHz. The devices maintain quite low leakage current density even under a high applied bias. The quality factor analysis shows that the device quality factor is highly dependent on conductor loss of electrodes at frequencies above 1 MHz. The phase shifter employing BZN/BST-based varactors exhibits lower insertion loss than does employing semiconductor diodes at a designed frequency of 445 MHz, demonstrating the potential of tunable capacitors employing BZN/BST thin films for RF applications.

High temperature degradation of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ membranes in atmospheres containing concentrated carbon dioxide

Degradation of microstructure and phase composition of perovskite-structured Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ membrane was investigated after exposure to CO 2-containing atmospheres in the temperature range of 800–900 °C. A carbonate surface layer was formed on the treated membrane. Adjacent to the carbonate layer is an intermediate decomposed zone, consisting of mainly CoO and a Ba–Sr–Co–Fe oxide compound as well as (Ba, Sr)CO 3 carbonate. Three different carbonate phases were observed, depending on the annealing conditions. The growth of both the carbonate top layer and the decomposed zone obeys a parabolic rate law, indicating a diffusion-controlled growth mechanism. The growth kinetics and mechanism are insusceptible to the change of partial pressure of oxygen and carbon dioxide under the given conditions. Deviation from the nominal composition was observed in this decomposed zone, which becomes more pronounced closer to the carbonate top layer. The carbonate layer was found to grow outward, which indicates outward diffusion of barium and strontium cations under their respective chemical potential gradient. Full substitution of Co by Fe in this material leads to reduced degradation rate in CO 2, which is consistent with the lowering of the chemical potential of the A-site cations. The adverse effect of CO 2 was found to be more pronounced at the grain boundaries of the membrane.

Ferroelectric Gated Electrical Transport in CdS Nanotetrapods

Complex nanostructures such as branched semiconductor nanotetrapods are promising building blocks for next-generation nanoelectronics. Here we report on the electrical transport properties of individual CdS tetrapods in a field effect transistor (FET) configuration with a ferroelectric Ba(0.7)Sr(0.3)TiO(3) film as high-k, switchable gate dielectric. A cryogenic four-probe scanning tunneling microscopy (STM) is used to probe the electrical transport through individual nanotetrapods at different temperatures. A p-type field effect is observed at room temperature, owing to the enhanced gate capacitance coupling. And the reversible remnant polarization of the ferroelectric gate dielectric leads to a well-defined nonvolatile memory effect. The field effect is shown to originate from the channel tuning in the arm/core/arm junctions of nanotetrapods. At low temperature (8.5 K), the nanotetrapod devices exhibit a ferroelectric-modulated single-electron transistor (SET) behavior. The results illustrate how the characteristics of a ferroelectric such as switchable polarization and high dielectric constant can be exploited to control the functionality of individual three-dimensional nanoarchitectures.

Electrical properties of metal–ferroelectric–insulator–semiconductor structure using Ba xSr 1−xTiO 3 for ferroelectric–gate field effect transistor

Perovskite ferroelectric Ba x Sr 1− x TiO 3 ( x = 0.5, 0.6, 0.7 and 0.8) thin films have been fabricated as metal–ferroelectric–insulator–semiconductor (MFIS) configurations using a sol–gel technique. The C– V characteristics for different Ba–Sr ratios and different film thicknesses have been measured in order to investigate the ferroelectric memory window effect. The results show that the memory window width increases with the increase both of Ba content and film thickness. This behavior is attributed to the grain size and dipole dynamics effect. It is found also that the memory window increases as the applied voltage increases. In addition, the leakage current density for the films is measured and it is found to be of the order of 10 −8 A/cm 2 for all tested samples, indicating that the films have good insulating characteristics.

The crystal structure of perloffite

AbstractThe structure of perloffite, ideally BaMn22+Fe23+(PO4)3(OH)3, has been solved and refined from single-crystal X-ray data collected on a Sr-bearing sample from the Spring Creek copper mine, near Wilmington, South Australia. A fragment of the crystal used for the collection of the X-ray intensity data was analysed by electron microprobe. The resulting unit formula is (Ba1.00,Sr0.03Σ1.03) (Mn2+1.15,Fe2+0.76Ca0.05Mg0.02,Na0.01)Σ1.99(Fe3+1.94,Al0.06)Σ2.00(PO4)2.99(OH)3.04. The structure is monoclinic. space group P21/m, a = 9.2425(18), b = 12.470(3), c = 5.002(1) Å, 0 = 100.19(3)°, V = 567.41(19) Å3, Z = 2, and was refined to R1 = 4.71% for 1568 unique observed reflections. The X site is [11]-coordinated and is occupied by dominant Ba and minor Sr, with an <X—O< distance of 2.953 Å. The Ml site is octahedrally coordinated and is occupied by Mn2+and Fe2+ plus minor Ca, Mg and Na with an observed <M1—O> distance of 2.208 Å. The M2 site is also octahedrally coordinated and is occupied by Fe3+ plus minor Al with a <M2—O> distance of 2.018 A. Perloffite is isostructural with other members of the bjarebyite group. Edge-linked [M22O6(OH)4] dimers link via corners to form chains along [010]. Chains are decorated with PO4 tetrahedra and link in the a direction via [M1O5(OH)] octahedra and (Ba,Sr) atoms to form a complex framework. The H2 atom hydrogen-bonds strongly to the O3 anion, providing additional linkage between chains.

Temperature effects on the band gaps of Lamb waves in a one-dimensional phononic-crystal plate (L)

This study investigates the temperature-tuned band gaps of Lamb waves in a one-dimensional phononic-crystal plate, which is formed by alternating strips of ferroelectric ceramic Ba(0.7)Sr(0.3)TiO(3) and epoxy. The sensitive and continuous temperature-tunability of Lamb wave band gaps is demonstrated using the analyses of the band structures and the transmission spectra. The width and position of Lamb wave band gaps shift prominently with variation of temperature in the range of 26 °C-50 °C. For example, the width of the second band gap increases from 0.066 to 0.111 MHz as the temperature is increased from 26 °C to 50 °C. The strong shift promises that the structure could be suitable for temperature-tuned multi-frequency Lamb wave filters.

Catena-Poly[[{bis[tetraaqua(2-hydroxy-3,4-dioxocyclobut-1-en-1-olato-κO1)bariumstrontium(0.35/0.65)]di-μ-aqua}bis(μ-2-hydroxy-4-oxocyclobut-1-ene-1,3-diolato-κ2O1:O3)] monohydrate

The title structure, {[Ba0.71Sr1.29(C4HO4)4(H2O)10]·H2O}n, is built from dimers of edge-sharing monocapped square anti­prisms [(Ba/Sr)O3(H2O)6], in which barium and strontium are statistically disordered [ratio 0.353 (8):0.647 (8)] on the same crystallographic site. Such dimers are connected via bidentate hydrogen squarate groups [HC4O4]−, leading to chains that propagate along the b axis. Inter- and intra­molecular O—H⋯O hydrogen bonds maintain the crystal packing through a three-dimensional network.

Vibrational modes and structural characteristics of (Ba0.3Sr0.7)[(ZnxMg1−x)1/3Nb2/3]O3 solid solutions

(Ba(0.3)Sr(0.7))[(Zn(x)Mg(1-x))(1/3)Nb(2/3)]O(3) (BSZMN) (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solution ceramics were synthesized by the conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy, short for FTIR) and X-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Mg(2+) ions replaced by Zn(2+) ions. It is verified that these ceramics present a phase transition, i.e., the crystal structure changes from hexagonal phase (P ̅3m1, where x≤ 0.4) to the pseudocubic phase (I4/mcm, where x≥ 0.8) with increasing Zn(2+) content. The phase transition is a gradual process, the sample where x = 0.6 is of the transition phase, i.e., at x = 0.6, phase transition begins to appear from hexagonal phase to pseudocubic phase but is not complete. The phase transition is also verified by the FTIR spectra. Tilting of oxygen octahedra is the main reason for the phase transition. The phonon modes of the vibration spectra were assigned, the position and width were determined, and the correlation of phonon vibrations with the microstructure for the different atoms substituted in B'-site was found.

Analysis of polarization behavior in relaxation of BaTiO3-based ferroelectrics using wideband dielectric spectroscopy

Wideband dielectric spectra from the kilohertz to terahertz range are discussed for BaTiO₃-based ferroelectrics. Ceramics of BaTiO₃ (BT), Ba(0.6)Sr(0.4)TiO₃ (BST-0.6), and BaZr(0.25)Ti(0.75)O₃ (BZT-0.25) were selected as normal ferroelectrics, ferroelectrics with diffuse phase transition (DPT ferroelectrics), and relaxor ferroelectrics, respectively. The variation of ionic polarization in both BT and BST-0.6 ceramics with temperature could be explained by the softening of the soft phonon mode. In BZT-0.25, a permittivity anomaly at the dielectric maximum temperature (T(m)) at low frequencies is not attributed to the softening of the soft phonon mode, but originates from the permittivity derived from the dipole polarization (ϵ(dipole)). Relaxor behavior in BZT-0.25 is derived from the increase in the depression of ϵ(dipole) on cooling across the T(m) with increasing frequency. In dipole polarization, BT, BST- 0.6, and BZT-0.25 all exhibited a similar tendency of ϵ(dipole) above the Curie temperature (T(c)) and T(m). However, behavior of ϵ(dipole) below the T(c) can be explained by the ferroelectric domains in BT, whereas the variation of ϵ(dipole) below the Tm could be explained by growth process of polar nanoregions (PNRs) in BST-0.6 and BZT-0.25. Regarding this, BT can be distinguished from BST-0.6 and BZT-0.25. Relaxation in BT could be interpreted as successive change in polarization mechanism from normal ferroelectrics to relaxor ferroelectrics via DPT ferroelectrics.

Material Properties and Structural Characterization of M3Si6O12N2:Eu2+ (M=Ba, Sr)—A Comprehensive Study on a Promising Green Phosphor for pc‐LEDs

The efficient green phosphor Ba(3)Si(6)O(12)N(2):Eu(2+) and its solid-solution series Ba(3-x)Sr(x)Si(6)O(12)N(2) (with x approximately = 0.4 and 1) were synthesized in a radio-frequency furnace under nitrogen atmosphere at temperatures up to 1425 degrees C. The crystal structure (Ba(3)Si(6)O(12)N(2), space group P3 (no. 147), a = 7.5218(1), c = 6.4684(1) A, wR2 = 0.048, Z = 1) has been solved and refined on the basis of both single-crystal and powder X-ray diffraction data. Ba(3)Si(6)O(12)N(2):Eu(2+) is a layer-like oxonitridosilicate and consists of vertex-sharing SiO(3)N-tetrahedra forming 6er- and 4er-rings as fundamental building units (FBU). The nitrogen atoms are connected to three silicon atoms (N3), while the oxygen atoms are either terminally bound (O1) or bridge two silicon atoms (O2) (numbers in superscripted square brackets after atoms indicate the coordination number of the atom in question). Two crystallographically independent Ba(2+) sites are situated between the silicate layers. Luminescence investigations have shown that Ba(3)Si(6)O(12)N(2):Eu(2+) exhibits excellent luminescence properties (emission maximum at approximately 527 nm, full width at half maximum (FWHM) of approximately 65 nm, low thermal quenching), which provides potential for industrial application in phosphor-converted light-emitting diodes (pc-LEDs). In-situ high-pressure and high-temperature investigations with synchrotron X-ray diffraction indicate decomposition of Ba(3)Si(6)O(12)N(2) under these conditions. The band gap of Ba(3)Si(6)O(12)N(2):Eu(2+) was measured to be 7.05+/-0.25 eV by means of X-ray emission spectroscopy (XES) and X-ray absorption near edge spectroscopy (XANES). This agrees well with calculated band gap of 6.93 eV using the mBJ-GGA potential. Bonding to the Ba atoms is highly ionic with only the 4p(3/2) orbitals participating in covalent bonds. The valence band consists primarily of N and O p states and the conduction band contains primarily Ba d and f states with a small contribution from the N and O p states.

Microstructure and dielectric tunable properties of Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composite

Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composite ceramics were prepared by a solid-state reaction method and their dielectric tunable characteristics were investigated for the potential application as microwave tunable materials. The addition of Mg(2)SiO(4)-MgO into Ba(0.6)Sr(0.4)TiO(3) forms ferroelectric (Ba(0.6)Sr(0.4)TiO(3))-dielectric (Mg(2)SiO(4)-MgO) composites and shifts the Curie temperature to a lower temperature. The dielectric constant and loss tangent of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)- MgO composites have been decreased and the overall tunability is maintained at a sufficiently high level. The microwave dielectric properties of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)-MgO composites were evaluated. Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composites have tunability of 9.2 to 10.5% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring a low dielectric constant.

Sol–gel synthesis and characterization of Ba (1− x) Sr xTiO 3 ceramics

Ba (1− x) Sr x TiO 3 ( x = 0, 0.1, 0.2, 0.3) nanopowders were synthesized from alkoxide solution precursor by sol–gel process. The Ba (1− x) Sr x TiO 3 powders calcined at 800 °C for 2 h were maintained in cubic phase and the cell parameters were in the range of 4.0282–3.9786. The effects of Sr doping and sintering temperature on structure and dielectric characteristics of the Ba (1− x) Sr x TiO 3 ceramics were investigated. The increase of Sr content in the Ba (1− x) Sr x TiO 3 ceramics causes the inhibition of grain growth and downward shift of Curie temperature ( T c). The T c shift rate is 2.5 °C/mol% with increasing Sr content. At T c, the dielectric constants of Ba (1− x) Sr x TiO 3 ceramics increase with the increasing of sintering temperature, and the highest permittivity (7032) is obtained for x = 0.1 sample sintered at 1400 °C.

Triassic granitoids in the eastern Songpan Ganzi Fold Belt, SW China: Magmatic response to geodynamics of the deep lithosphere

The Songpan Ganzi Fold Belt (SGFB), SW China, was developed from a passive continental margin into an orogenic belt with the consumption of the Paleo-Tethys. During the evolution of the SGFB, numerous Late Triassic granitic plutons formed and exhibited a progressive development from adakite/I-type granite, high Ba–Sr granite, A-type granite and monzonite. Representative Late Triassic plutons were studied to unravel the bewildering evolution of the eastern SGFB. The Menggu Pluton (224 ± 3 Ma) consists of granites with high alkali (K2O+Na2O = 7.85–10.4 wt.%) and adakitic characteristics (Sr/Y = 19–38). The εNdT values (− 2.77 to − 5.03), initial 87Sr/86Sr ratios (0.7050–0.7063) and low Nb/Ta ratios (8–10) are indicative of an origin by partial melting of amphibolitic lower crust. Rocks from the Niuxingou Pluton (215 ± 3 Ma) are richer in K than Na (K2O/Na2O = 1.1–1.5) and contain high Sr (1006–1662 ppm) and Ba (1277–2009 ppm), typical of shoshonite and high Ba–Sr granite. They have less enriched εNdT values (+ 0.08 to − 2.04) and less radiogenic 87Sr/86Sri ratios (0.7047–0.7048), and formed from a mixed melt derived from upwelling asthenosphere and the overlying metasomatised lithospheric mantle. The Taiyanghe Pluton (205 ± 3 Ma) consists of monzonites, with high Al2O3 (> 20 wt.%), but low MgO (0.94–1.39 wt.%). The rocks are richer in Na than K (K2O/Na2O < 0.7), contain high large ion lithophile element (LILE) (681–834 ppm Sr and 2142–9453 ppm Ba) and display strongly fractionated REE patterns ((La/Yb)N = 35–63). These features, together with their enriched Nd–Sr isotopic compositions (εNdT = − 4.78 to − 6.50; 87Sr/86Sri = 0.7074–0.7090), suggest that the monzonite probably formed from low degrees of partial melting of metasomatised lithospheric mantle. Although a continuous compressional regime during the Mid- and Late Triassic has been invoked for the SGFB, the generation of crustally derived adakitic and shoshonitic plutons reflect thickening in response to an arc-continental collision accompanied by fracturing of the lithosphere and an extensional regime in the deep lithosphere in the Late Triassic. The 205 Ma Taiyanghe Pluton was emplaced simultaneously with a rapid uplift of the lithosphere, when surface deposits changed from deep-water turbidite to tidal flat sediments. It was therefore generated during decompression, probably related to the rapid removal of the overthickened lithospheric mantle. The Triassic magmatism in the eastern SGFB is therefore important for probing geodynamic processes in the deep lithosphere.

A kinetic study of the decomposition of the cubic perovskite-type oxide BaxSr1−xCo0.8Fe0.2O3−δ (BSCF) (x = 0.1 and 0.5)

The decomposition of the cubic perovskite-type oxide Ba(x)Sr(1-x)Co(0.8)Fe(0.2)O(3-delta) (BSCF) into hexagonal and cubic perovskite-type phases has been examined by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED) and X-Ray Diffraction (XRD). SEM and TEM measurements reveal that the new hexagonal phase grows predominantly at the grain boundaries of BSCF ceramics and that the cation composition of the newly formed hexagonal phase differs from that of the starting material. An orientational relationship between the hexagonal and the parent cubic phase was also observed. By means of ex situ XRD the phase fraction of the hexagonal phase was determined as a function of annealing time. A kinetic analysis of the data, based on Avrami-type kinetics, indicates that the decomposition is independent of the initial A-site composition, and the obtained reaction order supports the conclusion that the hexagonal phase grows at the grain boundaries in dense ceramic samples.

Discrimination and origin of the sanukitoid series: Geochemical constraints from the Neoarchean western Karelian Province (Finland)

Neoarchean late to post-tectonic sanukitoid intrusions are found in the western part of the Karelian Province in Finland. Variable-sized, even-grained to K-feldspar porphyritic intrusions form a series of diorites, tonalites, and granodiorites, that are calc-alkaline to alkali-calcic, magnesian, and mostly peraluminous. The major and trace element geochemistry of the intrusions show typical sanukitoid affinities: a mantle signature (high content of Mg, Ni, Cr and high Mg#) and enrichment in LILE (especially K, Ba, and Sr). The intrusions form a distinctive series that can be distinguished from the TTG series of the Karelian Province by their high Ba–Sr signature, low Na 2O/K 2O ratio, and uniform HREE pattern. The sanukitoid series can be compositionally constrained as follows: SiO 2 = 55–70 wt.%, Na 2O/K 2O = 0.5–3, MgO = 1.5–9 wt.%, Mg# = 45–65, K 2O = 1.5–5.0 wt.%, Ba + Sr > 1400 ppm, and (Gd/Er) N = 2–6. The probable source was enriched subcontinental lithosphere mantle with high LILE concentrations in phlogopite and/or sanidine. The accumulation of K, Ba, and Sr in the mantle source may have occurred as a consequence of two separate metasomatic events: 1) by subduction-related fluids/melts and 2) by metasomatism related to asthenospheric mantle upwelling caused by slab breakoff. The slab breakoff at the end-stage of subduction is also a viable trigger for the sanukitoid magmatism.