Chemical capacitance proposed for manganite-based ceramics

The measured value of effective electric permittivity \varepsilon_{eff} of several compounds, e.g., (BiNa)(MnNb)O_{3}, (BiPb)(MnNb)O_{3}, and BiMnO_{3} increases from a value \approx 10-100 at the low temperature range (100-300 K) up to the high value reaching the value 10^5 at high temperature range, e.g., 500-800 K. Such features suggest the manifestation of thermally activated space charge carriers, which effect the measured capacitance. The measured high-value effective permittivity of several manganite compounds can be ascribed to the chemical capacitance C_{\mu}=e^2\partial N_{i}/\partial \mu_{i} expressed in terms of the chemical potential \mu. The chemical capacitance C_{\mu}^{(cb)} = e^2 n_{C}/k_{B}T depends on temperature when the conduction electrons with density n_{C} = N_{C} \exp(\mu_{n}- E_{C})/k_{B}T are considered. The experimental results obtained for the manganite compounds, at high temperature range, are discussed in the framework of the chemical capacitance model. However, the measured capacitance dependence on geometrical factors is analysed for BiMnO_{3} indicating that the non-homogeneous electrostatic capacitor model is valid in 300-500 K range.Comment: 10 pages, 7 figure

The composition induced crossover in nonlinear dielectric response in (1-x) Pb(Zr0.70Ti0.30)O-3-x BiMn2O5 (x=0, 0.02, 0.055, 0.11, 0.15, 0.22, and 1) ceramics

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O-3 (PZT), bismuth manganite (BM) and the composite (1 - x) PZT-x BM were obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a(3), was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a(3) was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a(3) was positive for BM and for the composite with sufficiently high BM content. The positive a(3) was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a(3) and for the colossal magnitude of the imaginary part of the linear dielectric susceptibility. The concentration of the ions was determined using scanning electron microscopy. The chemical disorder and the precipitation of ions determined using time of flight-secondary ion mass spectrometry correspond to a crossover in the electrical features

Effect of uniaxial pressure on the ferroelectric phase transition in Pb5Ge3O11 : Ba crystals

The effect of uniaxial pressure up to 1 kbar applied perpendicular and parallel to c-axis, on the Curie temperature and electric permittivity "c of Ba-doped Pb5Ge3O11 single crystals was investigated. The Curie temperature decreases with uniaxial pressure and the coe±cient °i (°i ´ ±Tc=±Xi) is determined as {7 and {11 K kbar¡1 for the b- and c-axes, respectively. It was found that uniaxial pressure increases the phase transition diffuseness and the tricritical point cannot be achieved for this pyroelectric and ferroelectric single crystal

ZUR STRATEGIE DER ENERGIEWIRTSCHAFTLICHEN ENTWICKLUNG KROATIENS

U Hrvatskoj ne postoji strategija razvitka energetike. Nedavno objavljeni tekst tzv. »Strategija energetskog razvitka« to također nije. U njemu su dane mnoge tvrdnje koje nemaju uporište u stvarnosti. Predviđanja potrošnje energenata i njihova zadovoljavanja u potpunosti su bez osnova. Nepostojanje strategije razvitka te gospodarske grane imalo je za posljedicu brojne promašaje što je rezultiralo previsokim cijenama energenata. Cijena električne energije za domaćinstva u odnosu na platežne mogućnosti stanovništva u Hrvatskoj u prosjeku je dva puta viša nego u razmatranim europskim zemljama, a cijena plina čak tri puta. S obzirom na »strategiju« može se očekivati još više cijene energenata.The author holds that there is no development strategy of power industry in Croatia. The document published under the title “Development Strategy of Power Industry” is not a strategy. The author believs that in this document some assertions were made without any reference to reality. On a number of data and analyses it has been shown that the predictions about the use of energy and meeting the needs for it are unrealistic. A lack of an appropriate strategy concerning power industry in Croatia has resulted in too high prices of energy. The price of electric energy for households is in relation with the populations\u27 buying power twice as high as in some European countries, and the price of gas three times. The author concludes that – considering the existing “strategy” – the prices of energy will rise in the period to come.Der Autor bringt die These vor, daß es in Kroatien keine Strategie einer energiewirtschaftlichen Entwicklung gibt. Das unter dem Titel “Strategie der energiewirtschaftlichen Entwicklung” veröffentlichte Dokument ist keine Strategie. Der Autor ist der Meinung, daß in diesem Dokument Feststellungen vorkommen, die keinen Realitätsbezug aufweisen. An einer Reihe von Daten und Analysen wurde gezeigt, daß die Vorhersagen über den Energieverbrauch und die Bedarfdeckung keine Grundlage haben. Das Ausbleiben einer echten Entwicklungsstrategie der Energiewirtschaft in Kroatien hatte zahlreiche Verfehlungen zur Folge, was zu verhältnismäßig hohen Energiepreisen führte. Der Preis des elektrischen Stroms für Haushalte ist im Verhältnis zur Zahlkraft der Bevölkerung in Kroatien zweimal so hoch wie in einigen anderen Ländern Europas, und der Gaspreis ist sogar dreimal so hoch. Der Autor kommt zu dem Schluß, daß aufgrund der bestehenden “Strategie” in der kommenden Zeit noch höhere Preise der Energie zu erwarten sind

Propedeutyka polityki środowiskowej

Streszczenie jest niedostępne

SCHUTZ UND BEVÖLKERUNGSRETTUNG IN KRISENZUSTÄNDEN. Krisenmanagement

U članku se razmatra potreba uspostave cjelovitog sustava zaštite i spašavanja stanovnika, dobara i okoliša u Republici Hrvatskoj na osnovi iskustava u uspostavi sličnih sustava u ekonomski razvijenim zemljama (poglavito u SAD-u) i iskustava iz domovinskog rata. Žrtve rata, problemi povratka prognanika i obnove razorenih dijelova Hrvatske te goleme štete izazvane mirnodopskim ugrožavanjima (suše, oluje s tučom, potresi...), koje u Hrvatskoj iznose više od 800 tisu}a US$ na dan, obvezuju da se u nas što prije uspostavi takav ili sličan sustav. Organiziranost svake zemlje za obranu i zaštitu njenih stanovnika, dobara i okoliša unutrašnja je stvar svake pojedine zemlje. Stoga svaka zemlja tu aktivnost mora organizirati tako da bude najdjelotvornija u obavljanju svoje zada}e, a u skladu s najprečim zadacima u pojedinoj zemlji, uz što manje troškove - što je posebno važno za ratom osiromašenu Hrvatsku. Uobičajena je praksa u svijetu da za upravljanje u kriznim (izvanrednim) stanjima postoji samostalno državno tijelo (ministarstvo, agencija-udruga) postavljeno vrlo visoko u državnoj hijerarhiji, s vrlo stručnim kadrom i iznimno velikim ovlastima za djelovanje.The article discusses the need to establish an integral system for protecting and rescuing of civil population, goods and environment in the Republic of Croatia, based on the experience made by high-developed countries (especially by the USA) and by Croatia during the defensive war. Victims of war, return of displaced persons to their homes and the reconstruction of the damaged regions of Croatia together with huge material damages caused by natural disasters in peace-time (droughts, hail-storms, earthquakes, etc.), which in Croatia amount to more than 800.000 a day, oblige Croatia to establish an identical or a similar system. The level of organization of each country in defending and protecting its citizens, goods and environment is an interior issue of a particular country. Thus each country should be done at minimal costs and in accordance with the most urgent tasks in a particular country. This is especially true of the war-impoverished Croatia. In many countries there is an independent state body to deal with emergency situations (ministry, agency, etc.). It takes a high position in the state hierarchy, is well equipped with professionals and exercises broad authorities.Im Artikel wird das Bedürfnis nach der Aufstellung eines einheitlichen Schutz- und Rettungssystems der Bevölkerung, der Güter und der Umwelt in der Republik Kroatien erläutert, und zwar aufgrud der Erfahrungen, die bei der Entwicklung ähnlicher Systeme wirtschaftlich hochentwickelte Länder (vor allem die Vereinigten Staaten) und Kroatien selbst im Verteidigungskrieg machten. Die Kriegsopfer, die Heimkehr Vertriebener, der Wiederaufba kriegszerstörter Gebiete Kroatiens und die durch in der Friedenszeit vorgekommene Heimsuchungen (Dürre, Hagelstürme, Erdbeben, usw.) entstandenen Sachschäden, die in Kroatien mehr als 800.000 Dollar pro Tag betragen, verpflichten Kroatien, demnächst ein solches oder ähnliches System aufzustellen. Inwieweit ein Staat Verteidigung und Schutz seiner Bevölkerung, seiner Güter und seiner Umwelt organisiert, gehört zu seinen Innenangelegenheiten. Deswegen soll ein jeder Staat diese Tätigkeit möglichst wirksam organisieren, und zwar im Einklang mit den wichtigsten Aufgaben im jeweiligen Staat, aber mit möglichst kleinem finanziellem Aufwand. Das ist besonders wichtig für das kriegsverarmte Kroatien. In vielen Ländern ist es üblich, da für das Management in Krisenzuständen ein selbständiger staatlicher Körper (Ministerium, Agentur, usw.) mit hochqualifiziertem Personal und besonders groen Zuständigkeiten eine hohe Stelle in der Staatschierachie einnimmt

Polityka ochrony środowiska w podstawach traktatowych UE

The article contains a presentation of the main documents of the European Union and analyses ecological policy and the problems of environmental protection in this regard

UNBEAUFSICHTIGTE BEFREIUNG GEFÄHRLICHER (TOXISCHER) STOFFE IN DIE UMWELT

U radu je riječ o potrebi uspostave učinkovitog sustava za zaštitu stanovnika, materijalnih dobara i okoliša u slučaju nekontroliranog oslobađanja opasnih tvari u okoliš. Takva sustava u nas nema zbog različitih razloga, od kojih su osnovni: nedovoljno znanje za uspostavu, nedorečeno zakonodavstvo i privatni interesi pojedinaca. Izloženi su osnovni elementi za uspostavu djelotvorna sustava: analiza opasnosti, ovlasti (zakonodavstvo), organizacija, komuniciranje, resursi i plan djelovanja u slučaju nekontrolirana oslobađanja opasnih tvari. Prikazani su dosezi zona ugroženosti u slučaju nekontrolirana oslobađanja opasnih tvari za pojedine pogone u gradu Zagrebu. Rezultati obvezuju na nužno informiranje javnosti o mogućim rizicima kao preduvjetu za njihovu učinkovitu zaštitu i hitno uklanjanje svih zapreka za uspostavu sustava zaštite.The article shows the urgency of establishing the efficient organization and management system of the protection of citizens, of material goods and of environment in case of uncontrolled hazard materials release. Such system has not been established in Croatia, yet, for various reasons, as for example: insufficient knowledge to start the establishment, absence of positive views in present law clauses and individual interests. In the text there are shown the elements for the establishment of the efficient emergency management organization as: analysis of dangers, authorities (law enforcement instances), organization, communication, resources and hazard emergency response plans in case of uncontrolled toxic materials release situations. The assessment of the vulnerability of the zones of particular plants within the Zagreb city limits in case of uncontrolled toxic materials release has been made in the text as well. The results point to the necessity of informing the public about the risks of such incidents, this being the essential condition for the breaking of existing barriers and for the establishment of the efficient hazard materials emergency management organization.In dieser Arbeit ist die Rede von der Notwendigkeit der Herstellung eines wirkungsvollen Systems zum Schutz der Einwohner, der materiellen Güter und der Umwelt im Falle einer Unbeaufsichtigten Befreiung von gefährlichen Stoffen in die Umwelt. Ein derartiges System gibt es bei uns aus verschiedenen Gründen nicht, und die wichtigsten davon sind ungenügende Kenntnisse zur Herstellung, eine nicht zu Ende ausgedrückte Gesetzgebung und private Interessen einzelner Personen. Es wurden die grundlegenden Elemente zur Herstellung eines wirkungsvollen Systems erläutert: die Gefahrenanalyse, die Befugnisse (die Gesetzgebung) die Organisierung, die Kommunikation, die Ressourcen ind ein Wirkungsplan im Falle einer unbeaufsichtigten Befreiung von toxischen Stoffen. Es wurde die Reichweite der gefährdeten Zonen im Falle einer unjbeaufsichtigten Befreiung von Giftstoffen für einzelne Betriebe der Stadt Zagreb dargelegt. Die Ergebnisse verpflichten zu einer besseren Informierung der Öffentlichkeit über die möglichen Gefahrenals Voraussetzung für ihren wirksamen Schutz und die dringende Beseitigung aller Hindernisse zur Herstellung der Schutzsystems

Crossover from Ferroelectric to Relaxor Behavior in Ba1−xCaxTiO3 (x = 0.17) System

The dielectric properties of Ba1xCaxTiO3 (x = 0.17) ceramics were studied in a wide frequency range of 20 Hz–53 GHz. Di used ferroelectric phase transition was revealed close to 339 K in the dielectric properties of ceramics. The behaviour of distributions of relaxation times in vicinity of the ferroelectric phase transition temperature is also typical for order-disorder ferroelectric phase transition. However, at lower temperatures (below 200 K), the most probable relaxation increased according to the Arrhenius law. At lower temperatures the maximum of the imaginary part of dielectric permittivity versus temperature strongly shifted to higher temperatures when the frequency increased (from 125 K at 1.21 kHz to 300 K at 33 GHz). This behaviour was attributed to the dynamics of Ti ions. The origin of the crossover from ferroelectric to relaxor behaviour of Ba1xCaxTiO3 (x = 0.17) ceramics is discussed in the paper