High pressure structural phase transition and electronic properties have been investigated using the linear combination of atomic orbitals (LCAO) method with two exchange-correlation approximations, the generalized gradient approximation (GGA) and local density approximation (LDA). The present study shows phase transitions from B1 to B27 and B27 to B2 at 6.24&#x2009;GPa and 16.39&#x2009;GPa, respectively. Lattice constant, bulk modulus, and energy gap of pressure-induced PbSe are found to be in good agreement with previous theoretical and experimental results. Variation of electronic band structure with pressure shows direct band gap along <i>L</i> point of the Brillouin zone.

P. Bhambhani

K. Kabra

B. K. Sharma

G. Sharma

High Pressure Study of Structural and Electronic Properties of PbSe

Combined optical and FTIR spectroscopy has been employed to investigate the undoped NaF-CaF<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> glass together with samples containing 0.2&#x25; dopant of 3d TM ions before and after gamma irradiation. The optical spectrum of the undoped glass reveals strong UV absorption with two peaks which are related to unavoidable trace iron impurity within the raw materials. Upon gamma irradiation, an induced visible broad band centered at 500&#x2009;nm is resolved and is related to B-O hole center or nonbridging oxygen hole center. TMs-doped samples exhibit characteristic absorption due to each respective TM ion but with faint colors. Gamma irradiation of TMs-doped samples reveals the same induced visible band at 500&#x2013;510&#x2009;nm in most samples except CuO and Cr<sub>2</sub>O<sub>3</sub>-doped glasses. Infrared absorption spectra reveal characteristic vibrational bands due to triangular and tetrahedral borate groups. The introduction of NaF and CaF<sub>2</sub> modifies the borate network forming BO<sub>3</sub>F tetrahedra. The introduction of 3d TMs as dopants did not make any obvious changes in the FTIR spectra due to their low content (0.2&#x25;). Gamma irradiation causes only minor variations in the intensities of the characteristic IR borate bands while the bands at about 1640&#x2009;cm<sup>&#x2212;1</sup> and 3450&#x2009;cm<sup>&#x2212;1</sup> reveal distinct growth in most samples.

F. H. A. Elbatal

M. A. Marzouk

Y. M. Hamdy

H. A. ElBatal

Optical and FT Infrared Absorption Spectra of 3d Transition Metal Ions Doped in NaF-CaF<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> Glass and Effects of Gamma Irradiation

Semiorganic nonlinear optical tris(thiourea) cadmium sulphate (TTCS) single crystals were grown by slow evaporation method. The crystal system, cell parameter of the grown crystal, was identified by powder X-ray diffraction study. The self-focusing <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.04981995pt" id="M1" height="9.38774pt" version="1.1" viewBox="-0.0498162 -9.33792 9.51013 9.38774" width="9.51013pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-91" d="M669 636L663 650H260C230 650 221 652 208 675H186C177 621 162 548 144 481L173 479C195 534 211 560 226 578C248 604 266 615 373 615H544C460 511 114 112 23 16L31 0H561C577 34 611 135 622 170L594 182C566 125 544 88 515 65C481 38 416 35 319 35C249 35 197 37 152 41C270 184 542 501 669 636Z"/></g></svg>-scan technique has been employed to observe the third-order nonlinear optical property of the grown crystal. The mechanical property of the grown crystal was examined by using Vicker&#x2019;s microhardness test. Chemical etching studies were made on the TTCS crystal using water as an etchant. The dark current and photocurrent properties of the crystal were estimated by using photoconductivity study. The dielectric constant of grown crystal was studied in different temperature by varying applied frequencies.

A. P. Arthi

M. Sumithra Devi

K. Thamizharasan

Structural, Microhardness, Photoconductivity, and Dielectric Properties of Tris(thiourea) Cadmium Sulphate Single Crystals

Quartz as a mineral has a stable crystalline phase at room temperature and atmospheric pressure; at low temperatures it is in the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129903pt" id="M3" height="6.42315pt" version="1.1" viewBox="-0.0498162 -6.21016 7.82384 6.42315" width="7.82384pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-223" d="M545 106L524 126C493 85 467 65 455 65C438 65 427 113 405 238C448 295 498 362 543 439L533 448L478 435C453 386 423 331 398 295H395C370 404 347 448 282 448C169 448 23 309 23 153C23 54 65 -12 128 -12C203 -12 283 70 339 155H341C360 29 380 -12 411 -12C444 -12 491 11 545 106ZM333 204C265 95 210 54 169 54C137 54 113 96 113 171C113 302 191 405 252 405C301 405 318 306 333 204Z"/></g></svg> phase and when it is heated up, it transforms into the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M4" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-224" d="M558 587C558 666 497 712 432 712C379 712 330 691 284 650C212 586 178 508 148 348L71 -65C49 -185 35 -229 23 -235L27 -261C49 -259 101 -251 124 -224C131 -216 138 -178 159 -24C171 66 197 200 227 356C264 550 295 668 393 668C443 668 479 632 479 575C479 516 446 458 383 418C361 404 344 398 318 397L296 350C395 338 460 281 460 192C460 110 411 40 300 40C258 40 215 55 192 69L181 51C191 18 222 -16 266 -16C308 -16 351 1 397 26C471 67 545 142 545 221C545 315 486 365 401 395C469 437 558 498 558 587Z"/></g></svg> phase through the intermediate (incommensurate)  phase within the temperature interval of nearly 1.3&#x2009;K at around 847&#x2009;K. The order parameter <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-2.23925pt" id="M5" height="11.2372pt" version="1.1" viewBox="-0.0498162 -8.99795 9.91808 11.2372" width="9.91808pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-82" d="M699 368C699 549 574 666 407 666C186 666 23 488 23 277C23 113 129 -3 288 -13L307 -26C431 -111 501 -139 533 -147C559 -154 613 -163 658 -164L666 -141C597 -111 507 -66 430 -11L416 -1C580 42 699 190 699 368ZM601 371C601 227 518 54 381 22L354 40L278 24C175 47 120 145 120 269C120 451 235 631 398 631C540 631 601 521 601 371Z"/></g></svg> occurs due to a tilting of SiO<sub>4</sub> tetrahedra around the threefold axis, which can be related to variation of the peak-intensity with the temperature in quartz. In this study, we analyze the temperature dependence of the Bragg peak-intensity measured through the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129903pt" id="M6" height="6.42315pt" version="1.1" viewBox="-0.0498162 -6.21016 7.82384 6.42315" width="7.82384pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-223"/></g></svg>-<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M7" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-224"/></g></svg> transition in quartz, as obtained from the literature according to a power-law formula. From our analysis, we deduce the values of the critical exponent <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M8" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-224"/></g></svg> for the order parameter (Bragg peak-intensity) for the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129903pt" id="M9" height="6.42315pt" version="1.1" viewBox="-0.0498162 -6.21016 7.82384 6.42315" width="7.82384pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-223"/></g></svg>-incommensurate (IC-)<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M10" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-224"/></g></svg> transition. Our <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M11" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-224"/></g></svg> values indicate that the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.571899pt" id="M12" height="13.2498pt" version="1.1" viewBox="-0.0498162 -9.6779 8.00062 13.2498" width="8.00062pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-224"/></g></svg>-IC phase transition is of a second order and that the IC-<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2129903pt" id="M13" height="6.42315pt" version="1.1" viewBox="-0.0498162 -6.21016 7.82384 6.42315" width="7.82384pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-223"/></g></svg> phase transition is of a weak first order, as also reported in the literature.

Hamit Yurtseven

Koray Kaymazlar

Temperature Dependence of the Bragg Peak-Intensity Close to the <svg  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.1993799pt" height="6.51834pt" version="1.1" viewBox="-0.0498162 -6.31896 8.04142 6.51834" width="8.04142pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g5-223" d="M563 442L553 454L479 439C463 404 440 354 416 322H414C389 422 344 454 283 454C151 454 21 310 21 162C21 48 73 -12 135 -12C182 -12 249 19 325 126H327C339 20 368 -12 407 -12C452 -12 507 21 557 110L530 136C508 107 493 92 480 92C462 92 453 123 430 253C459 292 528 386 563 442ZM318 186C290 133 235 76 202 76C175 76 154 108 154 184C154 275 198 406 247 406C288 406 313 294 318 186Z" /><glyph.data ascent="3481" descent="-2878" horiz-adv-x="584" vert-adv-y="584" /></g></svg>-Incommensurate-<svg  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.36801pt" height="13.0595pt" version="1.1" viewBox="-0.0498162 -9.69149 8.327 13.0595" width="8.327pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g5-224" d="M584 573C584 646 528 703 441 703C387 703 327 679 274 632C202 568 166 493 132 302L57 -122C43 -201 35 -214 21 -227L25 -246C54 -244 122 -236 156 -203C168 -191 175 -162 195 -40L261 369C291 556 318 652 391 652C431 652 465 620 465 543C465 497 449 456 408 422C395 411 364 405 340 403L309 336C386 319 447 279 447 188C447 105 419 50 329 50C290 50 253 63 226 77L216 55C218 23 252 -16 286 -16C324 -16 369 3 419 31C488 69 575 149 575 238C575 325 516 369 437 400C516 443 584 486 584 573Z" /><glyph.data ascent="3481" descent="-2878" horiz-adv-x="605" vert-adv-y="605" /></g></svg> Transition in Quartz

Structural formation of Bi<sub>1.65</sub>Pb<sub>0.35</sub>Sr<sub>2</sub>Ca<sub>4</sub>Cu<sub>5</sub>O<sub><i>y</i></sub> (2245 phase) superconducting compound was investigated by preparing the sample in a new matrix route. The phases formed at different intervals of heat treatment are monitored by X-ray diffraction studies. Bi-2212 phase was found to be the predominant phase till 20 hours of sintering at 850°C after which Bi-2223 phase was found to be the major phase. Traces of Ca<sub>2</sub>PbO<sub>4</sub> were also noticed along with 2212 and 2223 phases. For the first time, the highest <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42778pt" id="M1" height="12.7657pt" version="1.1" viewBox="-0.0498162 -9.33792 14.5489 12.7657" width="14.5489pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-85" d="M620 675H597C578 656 570 650 541 650H144C112 650 104 653 94 675H72C59 618 42 552 23 493L53 491C71 534 88 564 105 585C124 608 144 615 238 615H290L197 121C182 40 174 34 88 28L82 0H361L367 28C275 34 266 38 281 121L374 615H441C522 615 543 608 553 583C562 560 566 531 565 493L597 494C603 551 612 629 620 675Z"/></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><path id="g50-68" d="M690 629C653 643 577 667 483 667C225 667 24 528 24 292C24 92 174 -17 367 -17C448 -17 534 1 570 10C592 34 642 131 658 174C648 180 639 186 629 192C562 89 499 21 382 21C223 21 130 138 130 298C130 467 255 627 462 627C582 627 643 589 650 462L686 466C689 517 688 580 690 629Z"/></g></svg> onset of 127 K with maximum superconducting volume fraction was observed for the sample sintered at 850°C for 30 hours in this preparation. Further sintering is found to deteriorate the <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.42778pt" id="M2" height="12.7657pt" version="1.1" viewBox="-0.0498162 -9.33792 14.5489 12.7657" width="14.5489pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-85"/></g><g transform="matrix(.0095,0,0,-0.0095,7.479,3.264)"><use xlink:href="#g50-68"/></g></svg> onset value of the sample. There was no signature of the formation of 2234 or 2245 phase in this synthesis.

Ashoka Nukkanahalli Venkataswamy

George Thomas Chirayil

Srinivasan Kannaiyan

Investigation of Structural Formation of Starting Composition 2245 in the Bi-Pb-Sr-Ca-Cu-O System Superconductors

Irreversible quasi-surface metallurgical phase transformations are the specific response of some metallic materials&#x2014;such as metals and alloys&#x2014;subjected to high thermomechanical loads applied very near their surface during the manufacturing processes or after being put into operation. These solid/solid phase transformations can be observed, for example, on the tread of many rails in railroad networks frequented by freight trains. The severe thermal and mechanical loads imposed on the surface of the rails and in the immediate vicinity of the surface by the wheel/rail contact often result in highly localized irreversible metallurgical transformations. A new kinetic model based on a previous study is presented here, which accounts more realistically for the nucleation and growth of these irreversible solid/solid phase transformations resulting from high thermomechanical loads. This metallurgical behavioral model was developed in the framework of continuum thermodynamics with gradients of temperature and internal variables.

Gr&#xe9;gory Antoni

On a New Kinetic Modelling Approach of the Irreversible Quasi-Surface Metallurgical Phase Transformations

Polycrystalline ceramic samples of pure and germanium (Ge<sup>4+</sup>) doped fresnoite of general formula Ba<sub>2</sub>TiOSi<sub>2−<i>x</i></sub>Ge<sub><i>x</i></sub>O<sub>7</sub> (<svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.17555pt;width:49.237499px;" id="M3" height="11.125" version="1.1" viewBox="0 0 49.237499 11.125" width="49.237499">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,10.862)"><use xlink:href="#x1D465"></use></g><g transform="matrix(.017,-0,0,-.017,14.273,10.862)"><use xlink:href="#x3D"></use></g><g transform="matrix(.017,-0,0,-.017,28.977,10.862)"><use xlink:href="#x30"></use></g><g transform="matrix(.017,-0,0,-.017,37.137,10.862)"><use xlink:href="#x2E"></use></g><g transform="matrix(.017,-0,0,-.017,41.012,10.862)"><use xlink:href="#x30"></use></g>

		
	
</svg> and 0.2) have been prepared by solid state reaction technique. The formation of the single phase compound was confirmed by X-ray diffraction and the structural parameters were refined by the Rietveld refinement technique. The dc conductivity of both the materials has been measured as a function of temperature from room temperature to 753 K and activation energy was calculated using the relation <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.2316pt;width:80.4375px;" id="M4" height="12.325" version="1.1" viewBox="0 0 80.4375 12.325" width="80.4375">
	
		
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</svg>. The activation energy 4.74 eV obtained for the pure compound is very high in comparison with 1.47 eV of Ge<sup>4+</sup>-substituted compound. The frequency and temperature dependent dielectric behavior of both the compounds have been studied. The real and imaginary parts of the dielectric constant increase with the increase of temperature.

S. K. Barbar

M. Roy

Preparation and Electrical Properties of Ba<sub><bold>2</bold></sub>TiOSi<sub><bold>2&#x2212;</bold><italic>x</italic></sub>Ge<sub><italic>x</italic></sub>O<sub><bold>7</bold></sub> (<svg style="vertical-align:-0.17555pt" height="11.125" version="1.1" viewBox="0 0 49.237499 11.125" width="49.237499" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,10.862)"><path id="x1D465" d="M536 404q0 -17 -13.5 -31.5t-26.5 -14.5q-8 0 -15 10q-11 14 -25 14q-22 0 -67 -50q-47 -52 -68 -82l37 -102q31 -88 55 -88t78 59l16 -23q-32 -48 -68.5 -78t-65.5 -30q-19 0 -37.5 20t-29.5 53l-41 116q-72 -106 -114.5 -147.5t-79.5 -41.5q-21 0 -34.5 14t-13.5 37&#xA;q0 16 13.5 31.5t28.5 15.5q12 0 17 -11q5 -10 25 -10q22 0 57.5 36t89.5 111l-40 108q-22 58 -36 58q-21 0 -67 -57l-19 20q81 107 125 107q17 0 30 -22t39 -88l22 -55q68 92 108.5 128.5t74.5 36.5q20 0 32.5 -14t12.5 -30z" /></g><g transform="matrix(.017,-0,0,-.017,14.273,10.862)"><path id="x3D" d="M535 323h-483v50h483v-50zM535 138h-483v50h483v-50z" /></g><g transform="matrix(.017,-0,0,-.017,28.977,10.862)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g><g transform="matrix(.017,-0,0,-.017,37.137,10.862)"><path id="x2E" d="M113 -12q-24 0 -39.5 16t-15.5 42q0 24 16 40.5t40 16.5t40 -16.5t16 -40.5q0 -26 -16 -42t-41 -16z" /></g><g transform="matrix(.017,-0,0,-.017,41.012,10.862)"><use xlink:href="#x30"/></g></svg> and <svg style="vertical-align:-0.17555pt" height="11.125" version="1.1" viewBox="0 0 20.325001 11.125" width="20.325001" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,10.862)"><use xlink:href="#x30"/></g><g transform="matrix(.017,-0,0,-.017,8.222,10.862)"><use xlink:href="#x2E"/></g><g transform="matrix(.017,-0,0,-.017,12.098,10.862)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g></svg>) Ferroelectric Ceramics

We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices.

Martina De Laurentis

Andrea Irace

Optical Measurement Techniques of Recombination Lifetime Based on the Free Carriers Absorption Effect

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Journal of Solid State Physics