Dielectric and thermal behaviour of holmium tartrate trihydrate crystals

Abstract

Measurements on dielectric constant of holmium tartrate trihydrate crystals at frequencies of the applied a.c. in the range 1 kHz to 1 MHz and at temperature in the range 30°C to 330°C are reported. The dielectric constant ε' increases with temperature at all frequencies, attains a peak near 250°C, and then decreases as the temperature goes beyond 250°C. The anomalous dielectric behaviour at near about 250°C is attributed to be as a result of crystallographic/polymorphic phase transition brought about in the material. The results on the dielectric behaviour of the material are supplemented by results of thermal analysis viz., TG and DTA. Thermogravimetric and differential thermal analytic techniques have been used to study thermal behaviour of the material. It is shown that the material is thermally stable up to 220°C beyond which it decomposes through three stages till the formation of holmium oxide at 1200°C. The non-isothermal kinetic parameters e.g., activation energy and the frequency factor have been evaluated for first two stages of thermal decomposition by using the integral method of Coats and Redfern.

Structure, optical transition analysis and magnetic study of lanthanide based metal-organic framework: holmium bi-tartrate trihydrate

“…The measurement was performed over a sample weight of 5 mg by using the obtained crystals from 0 °C to 400 °C at a heating rate of 10 °C/ min in the nitrogen atmosphere.The synthesized metal-organic framework is thermally stable up to 240 °C followed by two endothermic peaks and an exothermic broad band highlighted as shaded portions as shown in figure 6. The thermal analysis for the synthesized MOF was found nearly consistent with the reported literature [34,35]. The first peak centered at 254 °C is attributed to water loss around the cationic sphere, and the second peak with centroid at 278 °C depicts the melting of synthesized metal-organic complex.…”

Studies on gel-grown pure and strontium-modified lanthanum tartrate crystals

“…The authors have taken measurements on dielectric constant of pure lanthanum tartrate and strontium-doped lanthanum tartrate in the temperature range 20-130 1C and under varying a.c. field from 1 to 1000 kHz. It is interesting that like other rare-earth tartrates [29][30][31], lanthanum tartrate shows a dielectric anomaly at about 102.47 1C. Further, doping the same with strontium (a ferroelectric material and having atomic radius (1.87Å) compatible with the atomic radius of (La 1.8Å)) increases the dielectric constant and shifts the temperature of dielectric anomaly towards a higher value [32].…”

Dielectric characteristics and thermal behaviour of terbium fumarate heptahydrate crystals

“…The advantage of a metal-organic hybrid system is the structural variability and tenability as the compounds can be grown from both inorganic and organic building blocks. In the class of metal-organic coordination compounds, rare-earth coordination compounds are the potential candidates, which besides showing dielectric and ferroelectric properties are also thermally stable [6,7]. A literature survey shows that there are interests in the research of coordination compounds from fumaric acid in the production of synthetic polymers and in the production of 3D framework structure [8,9].…”