Dobijanje provodne elektrokeramike na bazi barijum-stanata dopiranog antimonom sa linearnom strujno-naponskom karakteristikom

U okviru ove disertacije ispitivani su uticaji koncentracije dopanta i parametara sinterovanja na strukturu i svojstva keramičkih uzoraka barijum-stanata dopiranog antimonom, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 i 0,10) u cilju dobijanja provodne elektrokeramike sa linearnom strujno-naponskom (I-U) karakteristikom. Smeša prahova BaCO3, SnO2 i Sb2O3 mehanički je aktivirana u izopropanolu, kalcinisana na 900 °C i potom sinterovana koristeći tri različite metode: konvencionalno, spark plazma i hladno sinterovanje. Konvencionalno sinterovanje prahova vršeno je na 1200, 1400 i 1600 °C, ali se na nižim temperaturama dobija keramički materijal niskih relativnih gustina. Sinterovanjem na 1600 °C dobijeni su jednofazni uzorci kubne strukture BaSnO3 (BSO). Rezultati skenirajuće elektronske mikroskopije (engl. Scanning Electron Microscopy, SEM) ukazuju na značajno smanjenje veličine zrna nakon dopiranja, ali i na poroznost koja ometa električnu karakterizaciju uzoraka. Transmisiona elektronska mikroskopija visoke rezolucije (engl. High Resolution Transmission Electron Microscopy, HRTEM) ukazuje na prisustvo niskougaonih granica zrna u uzorku BaSn0,92Sb0,08O3. Pouzdana električna merenja izvršena na ovom uzorku ukazuju na njegova poluprovodnička svojstva karakteristična za materijale sa dvostrukom Šotkijevom barijerom (engl. Schottky barrier) na granici zrna. Spark plazma sinterovanje (SPS) vršeno je na temperaturama od 1000, 1100, 1200 i 1250 °C, za vreme od 5, 10, 15 i 30 min, pri pritisku od 60 MPa i sa brzinom zagrevanja od 100 °C min–1. Za dobijanje guste keramike optimalni uslovi sinterovanja su 1100 i 1200 °C, tokom 5 min. Sinterovanjem na 1100 °C dobijeni su jednofazni keramički uzorci kubne strukture BSO. Dopiranje antimonom dovodi do smanjenja veličine zrna, ali i do smanjenja specifične otpornosti u odnosu na nedopirani uzorak. Električna karakterizacija ukazuje na poluprovodnička svojstva svih keramičkih uzoraka, sa najnižom specifičnom otpornošću zabeleže
The main goal of this doctoral thesis was to investigate the influence of different dopant concentrations and sintering parameters on the structure and properties of antimony-doped barium stannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductive electroceramic samples with linear current-voltage (I-U) characteristics. A mixture of BaCO3, SnO2 and Sb2O3 powders was mechanically activated in isopropanol, calcined at 900 °C and then sintered using three different methods: conventional, spark plasma and cold sintering. Conventional sintering at 1200 and 1400 °C resulted in the preparation of low-density ceramic samples. By sintering at 1600 °C, single-phase material with a cubic BaSnO3 (BSO) structure was obtained. The scanning electron microscopy results (SEM) indicate a significant decrease in grain size upon doping but also reveal porosity, which hinders the electrical characterization of the samples. High resolution transmission electron microscopy (HRTEM) indicates the presence of low-angle grain boundaries (LAGBs) in the BaSn0.92Sb0.08O3 sample. Reliable electrical measurements performed on this sample indicate its semiconducting properties characteristic of materials with a double Schottky barrier at the grain boundary. Spark plasma sintering (SPS) was performed at temperatures 1000, 1100, 1200 and 1250 °C, for 5, 10, 15 and 30 min, at a pressure of 60 MPa and with a heating rate of 100 °C min–1. The most optimal conditions for the preparation of dense ceramic materials, in terms of temperatures and sintering time, were 1100 and 1200 °C for 5 min. By sintering at 1100 °C, single-phase ceramic samples with a cubic BSO structure were obtained. In comparison to the undoped sample, doping with Sb leads to a decrease in both grain size and electrical resisitivity. Electrical characterization shows semiconducting properties of all ceramic materials, with the lowest resistivity recorded for the BaSn0.92Sb0.08O3 sample. Apart from the cubic