Dielectric, elastic and optical properties of 80TeO2-(20-x) MnO2-xFe2O3 and 30Li2O-4MoO3-(66-x)TeO2-xV2O5 mixed oxide tellurite glasses in the conductivity anomaly region / Rosdiyana Hasham @ Hisam

Hasham @ Hisam, Rosdiyana (2017) Dielectric, elastic and optical properties of 80TeO2-(20-x) MnO2-xFe2O3 and 30Li2O-4MoO3-(66-x)TeO2-xV2O5 mixed oxide tellurite glasses in the conductivity anomaly region / Rosdiyana Hasham @ Hisam. In: The Doctoral Research Abstracts. IGS Biannual Publication, 12 (21). Institute of Graduate Studies, UiTM, Shah Alam.

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Abstract

In this study, two series of mixed oxide tellurite based glasses with composition 80TeO2-(20-x)MnO2-xFe2O3 (x = 5 mol% to 20 mol%) and 30Li2O-4MoO3-(66-x)TeO2-xV2O5 (x = 0.2–1.2 mol%) were prepared using melt-quenching method to investigate their dielectric, AC conductivity, elastic and optical properties. For the 80TeO2-(20-x)MnO2- xFe2O3 glass samples, the dielectric constant showed strong variation with Fe2O3 at a frequency ≥ 10 kHz, where ε′ decreased to a minimum value at x = 10 mol% before increasing for x >10%. The decrease in ε′ may be attributed to some form of hindrance effect on heavy dipoles caused by the mixed transition-ion effect (MTE). Meanwhile, variation of AC conductivity with Fe2O3 showed non-linear increase for x ≤ 10 mol% before dropping to a minimum at 15 mol% Fe2O3. This result is attributed to Anderson localization because of the disorder in the glass system. On the other hand, DC conductivity for the same glass system showed a strong increase for x ≤ 10 mol% Fe2O3 before reaching a saddle-like behavior between 10 mol % ≤ x ≤ 15 mol%, followed by a large increase for x > 15 mol%. Independent longitudinal modulus (CL), shear modulus (μ) and bulk modulus (Ke) showed increased values for x ≤ 10 mol% with an anomalous drop at x = 15 mol% Fe2O3, followed by a large increase at x > 15 mol%. The anomalous region between 10 mol% ≤ x ≤ 15 mol% coincided with DC conductivity saddle-like region and is suggested to be related to the MTE. Meanwhile, in the same region, optical band gap (Eopt) exhibited a maxima, whereas refractive index showed a minima, thereby indicating a variation in polarizability due to changes in concentration of bridging and non-bridging oxygens. For the 30Li2O-4MoO3-(66-x) TeO2-xV2O5 glasses, the variation of AC conductivity with V2O5 showed This thesis presents a simulation study on parameter estimation for binary and multinomial logistic regression, and the extension of the clustering partitioning strategy for goodness-of-fit test to multinomial logistic regression model. The motivation behind this study is influenced by two main factors. Firstly, parameter estimation is often sensitive to sample size and types of data. Simulation studies are useful to assess and confirm the effects of parameter estimation for binary and multinomial logistic regression under various conditions. The first phase of this study covers the effect of different types of covariate, distributions and sample size on parameter estimation for binary and multinomial logistic regression model. Data were simulated for different sample sizes, types of covariate (continuous, count, categorical) and distributions (normal or skewed for continuous variable). The simulation results show that the effect of skewed and categorical covariate reduces as sample size increases. The parameter estimates for normal distribution covariate apparently are less affected by sample size. For multinomial logistic regression model with a single covariate, a sample size of at least 300 is required to obtain unbiased estimates when the covariate is positively skewed or is a categorical covariate. A much larger sample size is required when covariates are 21 22 a non-linear increase for x ≤ 0.6 mol% before decreasing to a minimum at 0.8 mol% V2O5.

Item Type: Book Section
Creators:
CreatorsEmail
Hasham @ Hisam, RosdiyanaUNSPECIFIED
Subjects: Q Science > QD Chemistry > Physical and theoretical chemistry
Q Science > QD Chemistry > Analytical chemistry
Divisions: Institut Pengajian Siswazah (IPSis) : Institute of Graduate Studies (IGS)
Series Name: IGS Biannual Publication
Volume: 12
Number: 21
Item ID: 18958
Uncontrolled Keywords: Abstract; Abstract of Thesis; Newsletter; Research information; Doctoral graduates; IPSis; IGS; UiTM
Last Modified: 07 Jun 2018 01:44
Depositing User: Admin Pendigitan 2 PTAR
URI: http://ir.uitm.edu.my/id/eprint/18958

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